Omega Owners Forum

Chat Area => General Car Chat => Topic started by: Webby the Bear on 30 August 2012, 17:50:38

Title: Mechanic School Blog
Post by: Webby the Bear on 30 August 2012, 17:50:38
Hi guys,

Well tomorrow is my first day at Tresham College Wellingborough on the Level 1 Motor Vehicle Maintenance & Repair.

I have considered all my options re blogging with updates and I've gone off the Twitter idea due to the inability to upload photos. SO if it's ok with the mods I will use this thread as my blog and update accordingly.

It's been a long time coming and as a 29 year old it's now or never so I've got my new work boots, my boiler suit and my safety glasses (compulsary Personal Protection Equipment AKA - PPE). This is what I have bought:

(http://i1226.photobucket.com/albums/ee402/webbybear1/Coveralls.png)
I can't believe it was this cheap. I bought it from BACA which are a safety workwear company in Northampton. The material is quite thin but this for me is a must as I sweat unbelievably!

Boots - can't upload a photo but I got a decent pair of Toetectors and they're JCB. Don't want anything heavy breaking my foot! lol

Goggles - cheapo from B&Q

I also have my stationery but that's boring stuff lol

So I'll update what I've learned hopefully after each day and thought it would be nice to discuss various bits.

I also want to get you some cool shots of the workshop. They have all the gear including lifts, tyre and wheel balancing machines, alignment machines etc.

Well peace out for now and I'll update you as and when stuff comes up :)

Cheers.

Car Bear

Title: Re: Mechanic School Blog
Post by: henryd on 30 August 2012, 18:31:00
Good luck on your first day Webby,hope all goes well for you :y
Title: Re: Mechanic School Blog
Post by: b4ndit on 30 August 2012, 18:51:08
All the best and have fun :y :y
Title: Re: Mechanic School Blog
Post by: omega3000 on 30 August 2012, 18:52:08
All the best  ;)
Title: Re: Mechanic School Blog
Post by: Shackeng on 30 August 2012, 18:59:19
I'm looking forward to following your blog Webby, although I think from your posts that you have already got the hang of it. Best wishes :y
Title: Re: Mechanic School Blog
Post by: ozzycat on 30 August 2012, 19:40:19
 :y :y good luck mr bear you will enjoy it i hope :y :y :y :y
Title: Re: Mechanic School Blog
Post by: dbug on 30 August 2012, 20:00:25
Good luck with it Webby - someone has to go to Wellingborough :) :) ;)

Like your gear - sure you will look the DBs in that :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 30 August 2012, 20:01:04
Thanks for all the comments guys. really appreciated... hopefully i won't get pickedon by the older kids  ::) ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: albitz on 30 August 2012, 20:14:28
Head down the toilet on your first day. :P ;D............good luck with it. :y
Title: Re: Mechanic School Blog
Post by: martin42 on 30 August 2012, 20:23:16
Good luck mate  :y
Title: Re: Mechanic School Blog
Post by: Lazydocker on 30 August 2012, 20:24:09
Good luck Webby... Enjoy yourself!!!! :y :y
Title: Re: Mechanic School Blog
Post by: pauls on 30 August 2012, 21:55:19
Good luck and dont forget your lunch and a apple for the teacher ;D
Title: Re: Mechanic School Blog
Post by: omega3000 on 30 August 2012, 22:04:16
Good luck and dont forget your lunch and a apple for the teacher ;D

+ 1

 (http://i219.photobucket.com/albums/cc41/milleblack/bearbox.jpg)

Maybe there will be girlie mechanics on the course too  8)
Title: Re: Mechanic School Blog
Post by: henryd on 30 August 2012, 22:40:46
Head down the toilet on your first day. :P ;D............good luck with it. :y

Used to greasing of nuts in my day :-X :-\
Title: Re: Mechanic School Blog
Post by: Andy B on 30 August 2012, 23:11:02
.......

Used to greasing of nuts in my day :-X :-\

Yours or someone else's?  ??? ??? ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: plym ian on 31 August 2012, 07:40:30
goggles, steel toe boots, overalls that's hs gone mad next they'll say you can't smoke while working on engine ;D

all the bet and hope it goes well and don't let the bigger boys take your lunch money ;D
Title: Re: Mechanic School Blog
Post by: dbug on 01 September 2012, 01:27:58
How did your first day go Webby?  You back home yet?
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 01 September 2012, 19:39:57
Day 1:

Well, it wasn't the day of mechanical learning I was expecting  ::) They had us fill in a load of enrollment forms..... wtf couldn't they have sent them to us??? lol

Well anyway, I already made a new friend and the group for a load of young lads seem pretty cool and not ''rude boys'' thank God.


I thought it weird that when we were given our course code to put on the enrollment forms it was for the Level 2. Someone queried this before I did and low and behold everyone in my group has been moved up to Level 2 due to our previous GCSE/qualifications so I save a year and most importantly a years' tuition fee!  8)

Well I'm in all week next week so I'll update then. In the mean time got some more work to do on Ralf before I get rid of him.

Cheers guys

Oh ps, I was going to get some pics of the workshop but was a bit manic so didn't get the chance but I will on Monday. I realised there's actually 3 or 4 workshops and loads of hydraulic lifts. pretty big and i'm hoping they'll let me use them for my ATF change haha ;)
Title: Re: Mechanic School Blog
Post by: omega3000 on 01 September 2012, 20:44:10
Nice one , maybe you can get stuck in next week  8) We all wait in anticipation of your progress and an omega up on the ramps  :y
Title: Re: Mechanic School Blog
Post by: Steve B on 01 September 2012, 20:45:30
Day 1:

Well, it wasn't the day of mechanical learning I was expecting  ::) They had us fill in a load of enrollment forms..... wtf couldn't they have sent them to us??? lol

Well anyway, I already made a new friend and the group for a load of young lads seem pretty cool and not ''rude boys'' thank God.


I thought it weird that when we were given our course code to put on the enrollment forms it was for the Level 2. Someone queried this before I did and low and behold everyone in my group has been moved up to Level 2 due to our previous GCSE/qualifications so I save a year and most importantly a years' tuition fee!  8)

Well I'm in all week next week so I'll update then. In the mean time got some more work to do on Ralf before I get rid of him.

Cheers guys

Oh ps, I was going to get some pics of the workshop but was a bit manic so didn't get the chance but I will on Monday. I realised there's actually 3 or 4 workshops and loads of hydraulic lifts. pretty big and i'm hoping they'll let me use them for my ATF change haha ;)

can you not sort a oof ramp just for us for the duration of your course ;D ;D ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 01 September 2012, 21:04:29
ha ha yeah ill try and sort that lol ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 04 September 2012, 12:34:49
Day 2 to Day 6:

Well, unfortunately it's not exactly eventful on my Induction Week. So far we've had the tour (for about the thousanth time), been told that we can only smoke in the designated areas... I don't smoke, and finally we must wear our badges. Frankly this is really tedious.

HOWEVER there is some good news and some very good news:

Firstly, the guys on the course seem really cool. No problems from that aspect. And I've also realised that I definitely have the sense of humour of their age level... we were in the library and just at the point where the receptionist said ''and we inly allow screw top bottles, no cans at all'' someone cracked a can of Coke open. You had to be there  ::) ;)

Secondly, I get a Halfords Discount Card!  :) :) :) :) :) :) :) :) :) :) :) :) I haven't been issued with it yet but I have a feeling it's not the holy grail (Trade Card) and it is in fact something unique to the College; either way up to 30% off suits me!  :)

I think the teachers have recognised that I really want to get on and I'm motivated to getting as much out of the course as possible. Funilly enough the only bit of mechanic information so far was a mini quiz to see if the group knew anything already. I was the only one to pipe up on most of them  8)

SO as a bit of fun I'll give you the list of abbreviations and see how many you get right ;) (I got 5/7)

TDC
BDC
ATDC
CV
SV
CR
CC

Basically he explained that these are the main abbreviations used so before we're even set any proper work I'm taking it upon myself to learn these.

Also he added learning what a borre is (I know already), a stroke is (I know already) and what a Crankthrow is (no bleedin' clue :))

So, next Monday is the first day of practical.

I'll update then.

Peace out Bear lovers  :y
Title: Re: Mechanic School Blog
Post by: Rods2 on 04 September 2012, 16:20:08
Great to see you getting on really well.

How many safety lectures have you had so far?  ::)

Crank throw is the offset of a crank pin from the crank's centre line. 2 x crank throw is the stroke of the engine as this is the distance the piston moves from TDC when the crank throw is at the top to BDC when the crank throw is at the bottom of the engine.

http://en.wikipedia.org/wiki/Crankshaft (http://en.wikipedia.org/wiki/Crankshaft)

The animated diagram on this wiki page illustrates it well.
Title: Re: Mechanic School Blog
Post by: omega3000 on 04 September 2012, 18:24:02
Great your getting on and next week seems it will pick up and get those spanners turning  :y

Quote
someone cracked a can of Coke open. You had to be there 

 ;D :y
Title: Re: Mechanic School Blog
Post by: TheBoy on 04 September 2012, 18:39:14
Unfortunately, most technical course start slow, as they have to do all the tosh.

Remember, therory is probably more important than practical - truely understanding how it works. With experience, anyone can undo stuff ;)


So, Webby is doing all our ATF changes then :D
Title: Re: Mechanic School Blog
Post by: Lazydocker on 04 September 2012, 20:29:48
Unfortunately, most technical course start slow, as they have to do all the tosh.

Remember, therory is probably far more important than practical - truely understanding how it works. With experience, anyone can undo stuff ;)


So, Webby is doing all our ATF changes then :D

Corrected that phrase for you ;) ;)
Title: Re: Mechanic School Blog
Post by: TheBoy on 05 September 2012, 18:24:17
Unfortunately, most technical course start slow, as they have to do all the tosh.

Remember, therory is probably far more important than practical - truely understanding how it works. With experience, anyone can undo stuff ;)


So, Webby is doing all our ATF changes then :D

Corrected that phrase for you ;) ;)
I worded mine as I wasn't sure if Webby wanted to work in a dealer's service dept, or wanted to be a good mechanic.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 05 September 2012, 20:50:23
Cheers for the comments again guys, much appreciated. Yeah the aim is to become a mechanic and move up to Diagnostic Technician. But that's years off so for now I'll work hard towards getting the papers and take it from there. It is awesome as I already have access to mock exam papers. I'm going to give them a go to see where I am now  :y

So, I thought I'd put the answers to my little quiz bearing in mind I'm going to write them and print them off for review anyway.... you can help me with my questions in red  ;D  :)

TDC - Top Dead Centre - Now this is an interesting one. The technical answer to this (I think this is right) is that this is where the piston is at it's highest point in the cylinder. Now of course that's straight forward. However an interesting thought I had was this: Take a 4 pot engine and looking at the pistons travel cycle I see that two are moving up at the same time and two moving down at the same time (is this known as sister cylinders i believe??). Well when we put the crank at TDC for example when we're going to time them to the cams which two cylinders are at TDC? Surely on this basis the phrase ''getting the crank at TDC'' is wrong and it should be ''cylinders x & x are at TDC''?  

BDC - Bottom Dead Centre - again, like above this is the oposite where by the pistons are at their lowest posible point in the cylinder.

ATDC - After Top Dead Centre (or before) - This where the pistons are between their highest and lowest points. I put the crank at 60o ATDC on Ralf when I was sorting out his timing because I didn't want the valves to come in contact with the pistons when I was moving cam sprocket 1 up to the correct time (all in vain anyway as his valves were nackered already but still good to practise).

CV - Check Valve - this I'm unsure on. I've Googled this and the best explanation I can get is it's a valve that usually supplies fluid in one direction. So in an engine would this be a valve that shoots pressurised oil through it?  

SV - I can't find any explanation of this even in the Term Abbreviation tool i have lol... what is this?

CR - Compression Ratio - A nice easy one! Shown as a ratio a cylinders minimum and maximum volumes.

CC - Cubic Centimetre - and also this is used to describe Cylinder Capacity. I am actually looking at the formula at the moment which works out a cylinders displacement. It includes using PIE. God I aint had to use that for 15 years  ::) ;D Anyway I'll be looking at that next so will update at a later point.

Bore - The diameter of a cylinder
Stroke  - I may have got this wrong but is this the distance between the top of the piston (when it's at BDC) up to the top of the cylinder?

Crankthrow - Already experly explained by Rods2... thanks for that mate  :y

Apologies if any of that is wrong but I'm still learning so  :P :P :P ;D

Your input guys would be awesome as I need all the help I can get  :y

Oh and sadly I've still not been able to get pics of the workshops. Due to all the H&S lectures we aint been allowed in there again since our initial quick stop tour  ::) I'm in two minds about it really..... obviously I'm there to work on cars so I want to get cracking. But equally I'm a bit hesitant: School Kids + Machinery x Their Stupidity = Dead Bear.

Well anyways that's enough of me talking... gonna have a cold brewski and relax. love you all :)
xxx

Car Bear
Title: Re: Mechanic School Blog
Post by: Lazydocker on 05 September 2012, 21:00:20
TDC refers to No 1 cylinder ;)

All good info there Webby and it looks like you really do have the bug at the moment :y Best of luck
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 05 September 2012, 21:04:12
TDC refers to No 1 cylinder ;)

All good info there Webby and it looks like you really do have the bug at the moment :y Best of luck

Aaaaa-ha! that makes sense lol thanks LD  :y I like straightforward answers  ;D
Title: Re: Mechanic School Blog
Post by: dbug on 05 September 2012, 21:05:44
CV could well mean Constant Velocity as in CV Joint :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 05 September 2012, 21:07:11
CV could well mean Constant Velocity as in CV Joint :y

Cheers mate. i did see on the list it had that meaning as well. but i remember my tutor mentioning check valve so knew he wanted me to find out what that was  ;D
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 05 September 2012, 21:10:02
CV is Constant Velocity as in a constant velocity joint....as fitted to front wheel drive cars and very similar to the lobro type used on the omega rear drive shafts

Stroke is the distance the piston travels up the bore from BDC to TDC, its is not related to the bore as some pistons dont travel to the bore top (e.g. some low compression engines) and some travel beyond (e.g. some diesel engines)

TDC, BDC and ATDC (plus BTDC) are considered to be with reference to number 1 cylinder unless other wise stated (e.g. set no 2 cylinder to BDC)

SV is the swept volume and describes the volume of the area 'swept' by the cylinder.

All simples really  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 05 September 2012, 21:21:57
CV is Constant Velocity as in a constant velocity joint....as fitted to front wheel drive cars and very similar to the lobro type used on the omega rear drive shafts

Stroke is the distance the piston travels up the bore from BDC to TDC, its is not related to the bore as some pistons dont travel to the bore top (e.g. some low compression engines) and some travel beyond (e.g. some diesel engines)

TDC, BDC and ATDC (plus BTDC) are considered to be with reference to number 1 cylinder unless other wise stated (e.g. set no 2 cylinder to BDC)

SV is the swept volume and describes the volume of the area 'swept' by the cylinder.

All simples really  :y

Beautiful! Thanks mate!  :y :y
Title: Re: Mechanic School Blog
Post by: omega3000 on 05 September 2012, 21:32:51
Well done , keep up the good work ...im lost already  ;D :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 05 September 2012, 21:36:41
Well done , keep up the good work ...im lost already  ;D :y

cheers mate!  :y
Title: Re: Mechanic School Blog
Post by: grain.ben on 06 September 2012, 12:19:19
Good luck  :y
Title: Re: Mechanic School Blog
Post by: jonnycool on 06 September 2012, 14:56:09
I thought you liked a bit of PIE mate  ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 10 September 2012, 12:40:48
well after a week and a half i finally have some cool stuff to share with the class. We're currently taking a gear box apart. Will try and get some pics and do a proper update tonight but OMG the people who design these must be geniuses. We're struggling just to put it back together ha ha . Update tonight. Car bear x
Title: Re: Mechanic School Blog
Post by: omega3000 on 10 September 2012, 12:49:21
well after a week and a half i finally have some cool stuff to share with the class. We're currently taking a gear box apart. Will try and get some pics and do a proper update tonight but OMG the people who design these must be geniuses. We're struggling just to put it back together ha ha . Update tonight. Car bear x

Took a 4 speed off a capri and replaced it with a 5 speed cortina one once but never taken one to bits ... Hope your enjoying it all  :y
Title: Re: Mechanic School Blog
Post by: TheBoy on 10 September 2012, 12:49:54
TDC refers to No 1 cylinder ;)

All good info there Webby and it looks like you really do have the bug at the moment :y Best of luck
Any cylinder can be at TDC, but as Lazydocker says, if you see it written without being specific, its normally referring to No1 being TDC
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 10 September 2012, 15:53:54
well after a week and a half i finally have some cool stuff to share with the class. We're currently taking a gear box apart. Will try and get some pics and do a proper update tonight but OMG the people who design these must be geniuses. We're struggling just to put it back together ha ha . Update tonight. Car bear x

Took a 4 speed off a capri and replaced it with a 5 speed cortina one once but never taken one to bits ... Hope your enjoying it all  :y

Not much to them in reality, the clever bit is knowing how to shim and re-build them to get bearing loading and shaft end float correct
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 10 September 2012, 20:36:11
Evening chaps :)

Day 7:

Well we finally get our paws dirty in the workshop.

Our classroom within the workshop:
(http://i1226.photobucket.com/albums/ee402/webbybear1/coll4.jpg)
The workshop itself... there's a lot more to it than this (there's actually 4 workshops but this one's my class's) but I was limited to photos.... something about having to do work  ::)
(http://i1226.photobucket.com/albums/ee402/webbybear1/coll2.jpg)
Here's the transmission below:
(http://i1226.photobucket.com/albums/ee402/webbybear1/coll6.jpg)
And here;s a picture of the 4-speed transmission (from a ford I believe) following me adding some labdels from what i've learned....
(http://i1226.photobucket.com/albums/ee402/webbybear1/coll12.jpg)
Now please forgive me if I've got any of this wrong. But on the left is the input shaft. if my understanding is correct the power comes directly from the engine through this shaft and takes that power and transfers it to the output shaft which is the very large cogg on it's lonesome on the right and will be connected to the drive shaft which in turn goes to the wheels and the relevent diff. Now as this lesson was purely to learn about the tools (which i already know as they use the Hellfrauds 150 piece set) so in my own time I was quizzing the teacher and obviously there's only so much you can take in in one go so again apologies if I've got any of that wrong (maybe you could tell me if I'm right or not as every bit of knowledge helps ;))
In the picture also I've labelled the 4 gears... straightforward.
You'll note there are 2 arrow signs on the shaft where the gears live. These I believe are the gear selectors. SO again if my understanding is correct when gear 1 or 2 is selected the bottom most arrow showing 1 and 2 selector will ''latch on'' to the gear you've selected and rotate the shaft and output power. the upper most arrow does the same for gears 3 and 4. And when you put the clutch in or stick it in neutral the selector sits between the two gears and makes sure the shaft doesn't spin until a gear is selected and it can lock on to that gear.

We also took apart a carburettor but to be honest I didn't have time to quiz the teacher on this and I know everything's fuel injected anyway. Although when I did undo the bolts and prised it open there was the mini-est little gasket Ive ever seen; girls would call it cute!  ::) ??? :y

Anyways I got practival again tomorrow and unless any of you want me to list all the items in a Hellfrauds 150 piece that's today's update done.  :y
Title: Re: Mechanic School Blog
Post by: omega3000 on 11 September 2012, 09:30:17
Whats that red stand thing your holding onto in picture no2  :-\
Title: Re: Mechanic School Blog
Post by: tunnie on 11 September 2012, 09:32:07
Whats that red stand thing your holding onto in picture no2  :-\

Portable/moveable car lift  :y
Title: Re: Mechanic School Blog
Post by: tunnie on 11 September 2012, 09:33:28
Looking good Bear, are most there to train as mechanics to work in a garage?
Title: Re: Mechanic School Blog
Post by: omega3000 on 11 September 2012, 09:46:38
Whats that red stand thing your holding onto in picture no2  :-\

Portable/moveable car lift  :y

Ahrh i see ...thought it was a press or something  ;D :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 September 2012, 19:59:03
cheers guys, yeah that thing i think he called a part mover.... we put the gearboxes on and moved them around  :y

Tunnster, yes mate most of them are there to be mechanics but there are a couple of interesting potential careers namely two guys who want to be technicians for the RAF  :y

Day 8:

No point in really going through this as it's soul destroying stuff..... Risk Assessments  :'( :'( :'( :'( :'( :'(

it has made me recognise a few things but on the whole it's pretty darn boring. and i have a big assignment to do about just safety. OMG OMG OMG OMG  :'( :'( :'( :'( :'(
Title: Re: Mechanic School Blog
Post by: tidla on 11 September 2012, 21:17:01
Was going to come out with a quip like "some things are quite heavy". Then i remembered a post by Mr Wood about mixing certain garage chemicals which really are life threatening. Cannot for the life of me remember the detail.
Title: Re: Mechanic School Blog
Post by: aaronjb on 11 September 2012, 21:26:48
Was going to come out with a quip like "some things are quite heavy". Then i remembered a post by Mr Wood about mixing certain garage chemicals which really are life threatening. Cannot for the life of me remember the detail.

Thinking of this, maybe? http://www.brewracingframes.com/id75.htm - short version: brake cleaner containing chlorinated hydrocarbons decomposing to highly toxic phosgene gas during welding causing death and or serious lifetime health issues..
Title: Re: Mechanic School Blog
Post by: tidla on 11 September 2012, 21:32:44
Was going to come out with a quip like "some things are quite heavy". Then i remembered a post by Mr Wood about mixing certain garage chemicals which really are life threatening. Cannot for the life of me remember the detail.

Thinking of this, maybe? http://www.brewracingframes.com/id75.htm - short version: brake cleaner containing chlorinated hydrocarbons decomposing to highly toxic phosgene gas during welding causing death and or serious lifetime health issues..

Yep. :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 12 September 2012, 09:50:27
Dont get me wrong I'm fully aware of how dangerous most stuff for a car is. Hell i was in A and E a couple months back after shooting carb cleaner in my eye. But thing is I'm cautious of everything naturally and always pro actively think what i need to do to protect myself. It's just very very tedious having to write it down a thousand times lol
Title: Re: Mechanic School Blog
Post by: Lazydocker on 12 September 2012, 10:00:28
Dont get me wrong I'm fully aware of how dangerous most stuff for a car is. Hell i was in A and E a couple months back after shooting carb cleaner in my eye. But thing is I'm cautious of everything naturally and always pro actively think what i need to do to protect myself. It's just very very tedious having to write it down a thousand times lol
But that's the way the real world works now Bear ;) You should see some of the risk assessments I have to do (and have had to train my guys to do) when working on forecourts/roadside ::)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 12 September 2012, 10:14:16
ha ha yeah it's pretty sad aint it. I remember my dad telling me about his first day at work. They spent an hour risk assessing a hammer and listing it's uses. Wtf lol
Title: Re: Mechanic School Blog
Post by: biggriffin on 12 September 2012, 12:25:48
Risk assment  and eefing safety are the biggest money earners going. Get rid of no win no fee ambulance chasers and eefing safety wil disapear. When I was a boy we had a thing called common sense,but I'm not allowed to think for myself anymore I need a laminated plastic card telling me how/what do my job.
 its all to stop them being taken to court and having to pay compo.
.
. But that's my opinion.
Title: Re: Mechanic School Blog
Post by: plym ian on 12 September 2012, 13:37:05
Risk assment  and eefing safety are the biggest money earners going. Get rid of no win no fee ambulance chasers and eefing safety wil disapear. When I was a boy we had a thing called common sense,but I'm not allowed to think for myself anymore I need a laminated plastic card telling me how/what do my job.
 its all to stop them being taken to court and having to pay compo.
.
. But that's my opinion.
+1  :y

years ago if you had an accident at work say cut your finger off it would have been up the hospital sorted out back to work next day laughing and joking what a tit you'd been.

now it if you get so much as a paper cut its stop what your doing shut the factory down till hs have done a full investigation, compensation claim put in for loss of earnings, traumatic stress, counciling blah blah blah >:(

although a paper cut hurts more than losing actual finger or arm ;D ;D
Title: Re: Mechanic School Blog
Post by: omega3000 on 12 September 2012, 14:34:31
One of the courses i did had over 100 pages of health and safety reading to swot up on and answer to  >:( totally mind boggling and confusing ... nanny state says we need it  ::)

Risk assment  and eefing safety are the biggest money earners going. Get rid of no win no fee ambulance chasers and eefing safety wil disapear. When I was a boy we had a thing called common sense,but I'm not allowed to think for myself anymore I need a laminated plastic card telling me how/what do my job.
 its all to stop them being taken to court and having to pay compo.
.
. But that's my opinion.

Totally agree  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 September 2012, 21:40:05
Right then chaps, really looking for your help if possible  :) :) :)

is a parts washer to clean tools with?
Title: Re: Mechanic School Blog
Post by: albitz on 15 September 2012, 21:47:02
Clue is in the title webby, a parts washer is generally used for..................................washing parts. :D
Parts you take of an engine etc. which are coated in oil and grease. You drop them in there,switch it on and it cleans all the shite off. :y

http://www.machinemart.co.uk/shop/product/details/cw2d-bench-mounted-parts-washer?da=1&TC=SRC-parts washer
Title: Re: Mechanic School Blog
Post by: plym ian on 15 September 2012, 23:27:47
I suppose you could wash off a greasy tool in a parts washer ;D
Title: Re: Mechanic School Blog
Post by: omega3000 on 16 September 2012, 09:17:22
I heard a dish washer does a good job , obviously parts to be cleaned must be done while swmbo is out shopping  :-X :)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 16 September 2012, 09:44:18
Clue is in the title webby, a parts washer is generally used for..................................washing parts. :D
Parts you take of an engine etc. which are coated in oil and grease. You drop them in there,switch it on and it cleans all the shite off. :y

http://www.machinemart.co.uk/shop/product/details/cw2d-bench-mounted-parts-washer?da=1&TC=SRC-parts washer

Haha, yep, that is true; however due to the vast amount of ironies in life one assumes nothing  ;)

Ok, well I'm 7 questions in to a 17 question assignment  ::)

I'm kinda stuck.... does anyone know what cleaning products are used to specifically clean tools?
Title: Re: Mechanic School Blog
Post by: plym ian on 16 September 2012, 14:32:19
Clue is in the title webby, a parts washer is generally used for..................................washing parts. :D
Parts you take of an engine etc. which are coated in oil and grease. You drop them in there,switch it on and it cleans all the shite off. :y

http://www.machinemart.co.uk/shop/product/details/cw2d-bench-mounted-parts-washer?da=1&TC=SRC-parts washer

Haha, yep, that is true; however due to the vast amount of ironies in life one assumes nothing  ;)

Ok, well I'm 7 questions in to a 17 question assignment  ::)

I'm kinda stuck.... does anyone know what cleaning products are used to specifically clean tools?
whos doing this course us or you ;D

do we get any credit if you get it right ;D

anyway the answer is mr muscle loves the jobs you hate or clit cilt bang, bang and the dirts gone ;D

im not being much help am i :)
Title: Re: Mechanic School Blog
Post by: omega3000 on 16 September 2012, 14:50:10
Clue is in the title webby, a parts washer is generally used for..................................washing parts. :D
Parts you take of an engine etc. which are coated in oil and grease. You drop them in there,switch it on and it cleans all the shite off. :y

http://www.machinemart.co.uk/shop/product/details/cw2d-bench-mounted-parts-washer?da=1&TC=SRC-parts washer

Haha, yep, that is true; however due to the vast amount of ironies in life one assumes nothing  ;)

Ok, well I'm 7 questions in to a 17 question assignment  ::)

I'm kinda stuck.... does anyone know what cleaning products are used to specifically clean tools?
whos doing this course us or you ;D

do we get any credit if you get it right ;D

anyway the answer is mr muscle loves the jobs you hate or clit cilt bang, bang and the dirts gone ;D

im not being much help am i :)

 ;D ;D

I just use a rag and some WD if its thick grease  :-\ old boys use to use paraffin  :-\
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 16 September 2012, 16:07:30
Well i paid for the course, i aint doing the work too!  :P :P :P ;D ;D ;D

i think i got it. once ive done it would anyone be interested if i posted the questions and answers? :)
Title: Re: Mechanic School Blog
Post by: TheBoy on 16 September 2012, 18:57:10
I'm kinda stuck.... does anyone know what cleaning products are used to specifically clean tools?
I use:

http://www.finish.co.uk/finish_powerball_classic_dishwasher_tablets.php

;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 16 September 2012, 19:02:45
I'm kinda stuck.... does anyone know what cleaning products are used to specifically clean tools?
I use:

http://www.finish.co.uk/finish_powerball_classic_dishwasher_tablets.php

;)

I thank you for the sentiment mate... but if I put tools in the dishwasher I would be single quite quickly.....

Hmmmm..... (dons thinking cap)
Title: Re: Mechanic School Blog
Post by: dbug on 16 September 2012, 19:58:53
I suppose you could wash off a greasy tool in a parts washer ;D

Have to say wouldn't put my tool in a parts washer - but each to their own ;)  ;D ;D ;D  ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 September 2012, 16:24:24
right lads. Just in the pub for a couple of pints after a good days graft. Will give full update with lots of photos tonight as i have some really cool stuff to share with you :-) x
Title: Re: Mechanic School Blog
Post by: omega3000 on 18 September 2012, 17:20:38
Hurry up  ::) ;D

(http://i15.photobucket.com/albums/a384/themarbleintheoatmeal/smilies/watchdrama8jm.gif)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 September 2012, 20:00:57
Hurry up  ::) ;D

(http://i15.photobucket.com/albums/a384/themarbleintheoatmeal/smilies/watchdrama8jm.gif)

hahaha i fekking love that popcorn smilie  ;D ;D ;D ;D

just typing up the last two days events now.... awaiting downloads for photos  ::)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 September 2012, 20:40:54
right, looks like the update wont be tonight bar a miracle that my phone decides to stop being a potato and decides to be a useful working phone again :(
Title: Re: Mechanic School Blog
Post by: omega3000 on 18 September 2012, 20:50:41
right, looks like the update wont be tonight bar a miracle that my phone decides to stop being a potato and decides to be a useful working phone again :(

No problemo (http://i238.photobucket.com/albums/ff230/mikep37013/Mini%20Dancing/GoalMiniDancingBear.gif) just going to dance all night
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 21 September 2012, 23:27:44
evenin chaps. I will do full update tomorrow. Sadly my main omega has been giving me Shit this week so not had chance to update. However there was one thing i thought I'd quickly mention that shocked the Shit outta me assuming I've got my figures right. I queried in class the meaning of RPM. tutor told me that RPM was the number of full 360 turns the crank shaft makes per minute. So say you were in park and kept your foot on accelerator at 3k rpm that means that crank is doin 3000 full 360 turns a minute lol. And again if my maths is correct that would mean that one piston would move 100 times a second in the cylinder. I knew engine's were awesome but that takes the biscuit lol
Title: Re: Mechanic School Blog
Post by: plym ian on 21 September 2012, 23:46:11
isn't it 50 per second not 100

you failed ;D ;D
Title: Re: Mechanic School Blog
Post by: plym ian on 21 September 2012, 23:48:04
or did I fail is it 50 times up and 50 times down equaling a hundred :-\
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 21 September 2012, 23:50:12
yep 50 up and 50 down totalling on hundred strokes :-)
Title: Re: Mechanic School Blog
Post by: tidla on 22 September 2012, 00:07:41
For those joining the thread at page 6..

The discussion is engine revolutions per minute.
Title: Re: Mechanic School Blog
Post by: albitz on 22 September 2012, 00:22:27
Webby,if you still have Ralf and the heads are off ? get someone to turn the engine over on the starter for a few seconds and you will probably be surprised how quickly the pistons go up & down the bores even just at a speed which would hardly register on the rev counter. :y
Title: Re: Mechanic School Blog
Post by: omega3000 on 22 September 2012, 08:28:44
Hmmm , got me thinking so how would you measure if the car is performing the correct rpm ... strobe or something  :-\ Keep up the good work mate and pick that tutors brain  ;)
Title: Re: Mechanic School Blog
Post by: 78bex on 22 September 2012, 17:58:30
It`s great learning new stuff
Go for it now....... in 5 years time you`ll thank yourself for doing it.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 22 September 2012, 21:47:51
Day 9 to 11...... finally I hear you say  ::)

Ok well as I mentioned I have had a H&S Assignment to do. All done and handed in  8)

However, on Monday we started engine work. Day 9 to 10 was practical and Day 11 was theory.

This is the pushrod engine (from a Ford Fiesta I believe)....
(http://i1226.photobucket.com/albums/ee402/webbybear1/23_zps79b3074e.jpg)

This is the little engine shop...when I say engine shop it's just a room full of engines on lifts specifically there to work on... as you can see my mates are working hard while i take a breather to take the photo  ::) 8)

(http://i1226.photobucket.com/albums/ee402/webbybear1/15_zps039f0cb0.jpg)

This is us after we'd ripped the head off and we were able to turn the engine over on it's special mount, pull the sump off to reveal the holy grail of shafts  8) 8) 8). I found out that those bracket looking things with the big bolts are the big end bearings.  8) and they attach to the con rod.

(http://i1226.photobucket.com/albums/ee402/webbybear1/16_zpsebd43717.jpg)

ooooh....a quick shot of the head off....  8) 8) 8)

(http://i1226.photobucket.com/albums/ee402/webbybear1/21_zps605fa3fb.jpg)

This is me and my new friend lol i removed the clutch and fly wheel, timing gears and crankshaft..... and then he takes the photo plaudits  ::) ;D

(http://i1226.photobucket.com/albums/ee402/webbybear1/14_zps2ed92eb2.jpg)

This was day 10..... we'd put back together the bottom end including timing up the timing gears and putting the sump back. all nice n tidy and then we set about taking the valves out of the head and removing the collets by using the valve spring compressors.....

(http://i1226.photobucket.com/albums/ee402/webbybear1/13_zpsb94c286c.jpg)

....then we got the valve, covered the valve stem in grinding paste and used a stick to twist the paste in to the valve seat until it turned from ''rough'' to ''fine'' and this apparently is making sure the valve seats perfectly.....

(http://i1226.photobucket.com/albums/ee402/webbybear1/12_zpse77e0aca.jpg)


Anyway, as mentioned before in theory i learned about RPM..... unbelievable as mentioned before.

but most importantly i learned about the four stroke cycle (suck, squeeze, bang, blow  ;D ;D ;D ;D) and we'll be doing more theory on that as it was just an introduction to it this week.

as i mentioned before i have completed the H&S assignment. although its not interesting i do plan on posting my assignment on line for completeness and for any real boring b......s there are on the forum  ;D ;D ;D ;D

Title: Re: Mechanic School Blog
Post by: omega3000 on 23 September 2012, 08:29:12
At least your getting into the swing of things now the H&S >:( is out the way , when we did auto mechanics we had a triumph stag to work on ...it was the tutors  ;D :y
Title: Re: Mechanic School Blog
Post by: TheBoy on 23 September 2012, 09:36:55
At least your getting into the swing of things now the H&S >:( is out the way , when we did auto mechanics we had a triumph stag to work on ...it was the tutors  ;D :y
The boring H&S is useful, and should be adhered to...

...says TB, looking out of one eye, after pouring all the rust from tunnie's exhaust in one ;D
Title: Re: Mechanic School Blog
Post by: Lazydocker on 23 September 2012, 11:49:35
At least your getting into the swing of things now the H&S >:( is out the way , when we did auto mechanics we had a triumph stag to work on ...it was the tutors  ;D :y
The boring H&S is useful, and should be adhered to...

...says TB, looking out of one eye, after pouring all the rust from tunnie's exhaust in one ;D
Yep... "Gay" glasses have their uses ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 23 September 2012, 11:52:36
Haha yep they should be adhered to.... but it aint 'alf boring.

Also I believe I misquoted in one of my photos....

The one where I said we had the sump off to reveal the crankshaft.... the big end bearings are not the ones with the big bolts.... theyre actually the ones that are being undone by dumb and dumber to get the pistons out  8)
Title: Re: Mechanic School Blog
Post by: Shackeng on 24 September 2012, 12:59:01
They are, I believe, the main bearing retaining bolts. :y
Title: Re: Mechanic School Blog
Post by: aaronjb on 24 September 2012, 14:44:54
(http://i1226.photobucket.com/albums/ee402/webbybear1/16_zpsebd43717.jpg)

Main bearing retaining bolts are the large bolts sitting on the main bearing caps in this picture - 8 of them and they hold the crank into the engine.

What you're (well, your assistant ;D) busily undoing are the big end bearing caps (big end bearing being at the larger end of the con rod and holding the rod to the crank) - which is I think what you corrected yourself to say and what Shackeng also said.. but I just felt like saying it again ;D
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 24 September 2012, 14:55:35
Hateful shitty old engines those old Ford pushrod engines
Title: Re: Mechanic School Blog
Post by: 05omegav6 on 24 September 2012, 16:26:19
At least your getting into the swing of things now the H&S >:( is out the way , when we did auto mechanics we had a triumph stag to work on ...it was the tutors  ;D :y
The boring H&S is useful, and should be adhered to...

...says TB, looking out of one eye, after pouring all the rust from tunnie's exhaust in one ;D
Yep... "Gay" glasses have their uses ;)

True, but even they won't keep sparks from a grinding wheel or drill bit shrapnel away from your face :-X
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 24 September 2012, 21:08:27
Day 12 (Today): Help and input from you guys in red  :y ;D

Well, another awesome day of just practical  8) 8) 8)

So I finished off putting the collets back on to the valves (I had just two left from last week) using the valve spring compressor. just a brief reminder that we'd got the valves out so we could ''lap them in'' which means we were using that grinding paste to make the seat perfect........We then put the HG on the block and then the head and then torqued it up... standard spiral to 30nm, 90o, 90o. we then put the pushrods back in, then the rocker shaft.

We then got the engine hoist out to lift the engine back up on the stand.... i did tell my mate to get out of the way as he was ruining the shot  ::) Also was interesting that the engine didn't have its own lifting eyes but they had a box of them. we simply found two, put one through an exhaust manifold stud, and the other on an intake manifold stud, put nuts on them and began lifting ;)

(http://i1226.photobucket.com/albums/ee402/webbybear1/COLLEGE12.jpg)

So then when we'd put our engine back we had purposely left the valve cover off as our teacher showed us how to gap the valves. a note worth making for reference is that the inlet valves are always bigger than the exhaust valves so they can pull more mixture in. also if the exhaust valves were as big (or bigger) apparently they would get too hot..... got to be honest not too sure why  ???
Anyhow because the exhaust valve expands more in use we set that at 0.3mm and the inlet valve gap at 0.2.... when i say gap i mean the gap between the rockers and the top of the valves  :y and we used these feeler gaugers (i think thats what theyre called) to get the right gap.......
(this pic was actually taken from our second valve gapping job which we actually did on an engine in a car... another Ford Fiesta) its also worth noting that the bolt the socket is on we simply tightened if there was too much of a gap and unscrewed that if we wanted to make a bigger gap if it was too close). one final note is that the gapping of valves is mainly done on pushrod engines as most SOHC & DOHC have hydraulic lifters that are serviced differently and ultimately dont need gapping.
ooooooooooh one really important thing i nearly missed....... to do the gapping on we had to have the valves we were working on with that cylinder at TDC on compression stroke. and we used a method called ''ON THE ROCKS''  8). And it goes like this....
Cylinder 1: we turn the engine by hand and watch it's sister cylinder (cylinder 4) close it's exhaust valve and just open it's inlet valve. we now know cylinder one is at TDC and on it's compression stroke and therefore we're ready to gap cyliner 1. repeat for other cylinders.
(http://i1226.photobucket.com/albums/ee402/webbybear1/COLLEGE10.jpg)

This is a pic of the Fiesta Engine. note the battery is missing, however due to some good old charm and a bit of persistance i got a battery... and the keys  8) I have to say that even though i didnt hear the car before we'd done the job it sounded really sweet after the job!
A note about this engine which i completely didnt understand.... you see the oil filler cap.... there are two pipes going from this in to the intake. one you can see (short thin pipe to the left) and then one thick pipe which you cant see going from the oil filler tube to the right near the MAF on the right near where the battery should be. any ideas why this is?????
(http://i1226.photobucket.com/albums/ee402/webbybear1/COLLEGE11.jpg)

ok, so then we moved our trail of destruction mechanics skills to a corsa  ::). 4 pot, DOHC.....
(http://i1226.photobucket.com/albums/ee402/webbybear1/COLLEGE9.jpg)

Took the valve cover off this bad boy...... how many fekking bolts  :o and were greeted with.....(soz for the shite photo)
(http://i1226.photobucket.com/albums/ee402/webbybear1/COLLEGE8.jpg)

now this was interesting. the teacher rushed this a bit so i didnt quite get it so if anyone cares to explain that would be great. but basically we got a small screwdriver and under each cam lobe (when both dual cam lobes weren't opening valves) we pushed something to the right and back in place. if it clicked, which they all did, they were good  :-\ :-\ :-\ :-\ :-\ sorry for the crap explanation but i'm struggling myself with what happened  ;D

Anyway thats enough action for one day. some good work done. will update tomorrow as we hae more practical  8) 8) 8) 8) 8) 8)

Car Bear


Title: Re: Mechanic School Blog
Post by: Kevin Wood on 24 September 2012, 21:16:28
The pipes into the oil filler cap are the crankshaft breathers on this engine... They're not very effective, and Ford owners don't believe in oil changes, so you'll normally find a large buildup of very black margarine under the rocker cover. ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 24 September 2012, 21:18:46
Two quick things I forgot to mention....

1. when we'd done our valve gap job on the fiesta we'd put the HT leads round the wrong way... they weren't numbered sadly. however when we started it up it woudn't idle  ??? however when i put them the correct order it idled sweetly at 1000rpm. why is that? i thought we'd just be down a pot on power and maybe hear a machine gunning type sound as the sparks fly???

2. on that corsa valve cover is a gasket very similar to the CC Gasket for the mig. however those half moons were at the front of the engine so very easy to see whether they were sat in place correctly  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 24 September 2012, 21:20:31
The pipes into the oil filler cap are the crankshaft breathers on this engine... They're not very effective, and Ford owners don't believe in oil changes, so you'll normally find a large buildup of very black margarine under the rocker cover. ;D

 ;D

Thanks Kevin. why circulating back in to the intake though? i asked if this was this cars version of EGR but i was told a definite no. but thats what it sounds like  ???
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 24 September 2012, 21:23:08
Oh yes, setting the valve clearances on those engines is pretty hopeless using feeler gauges.

The ony effective way is with gauge wires whilst presing gently on the adjuster bolt as the rockers are shite and wear grooves in them where they rub on the valve stem tops.......and hence why most KA's rattle (they have this dog of an engine that should have been retired 25 years ago!).

With leads wrong, you wont be lighting the fuel mix (if at all!) on the correct cycle (remember your suck-squeeze-bang-blow)

Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 24 September 2012, 21:24:34
The pipes into the oil filler cap are the crankshaft breathers on this engine... They're not very effective, and Ford owners don't believe in oil changes, so you'll normally find a large buildup of very black margarine under the rocker cover. ;D

 ;D

Thanks Kevin. why circulating back in to the intake though? i asked if this was this cars version of EGR but i was told a definite no. but thats what it sounds like  ???

Crank case gases have to be re-cycled via the inlet for 'environmental' purposes, years ago they were vented to atmosphere resulting in oil spraying about and gases escaping.

They are (trying) to do the same job as the breathers on the Omega
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 24 September 2012, 21:27:03
That all makes sense, thanks Mark. so if we consider this as an ''accompaniment'' to the EGR that the omega has?

as for the 4 stroke cycle, yes thats true... if i'd mixed the minimum amount of leads that would mean the spark plug isnt igniting on at least two cylinders. soz its been a long day  ::) :y
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 24 September 2012, 21:28:27
The pipes into the oil filler cap are the crankshaft breathers on this engine... They're not very effective, and Ford owners don't believe in oil changes, so you'll normally find a large buildup of very black margarine under the rocker cover. ;D

 ;D

Thanks Kevin. why circulating back in to the intake though? i asked if this was this cars version of EGR but i was told a definite no. but thats what it sounds like  ???

I can't remember exactly how it works as, thankfully, my days of maintaining that car ended when it was made a couple of feet shorter. ;D

Incidentally, it had tried to kill itself once before that when the oil got into such poor condition that one of the big ends seized and it suffered a leg out of bed (connecting rod through the side of the block leaving a fist-sized hole).

I think you'll find one of those breather pipes comes from before the throttle, I.E. air filter box or ducting, and one comes from a small jet after the throttle, i.e. the throttle body or intake manifold. It's simply a case that one pipe creates a slight vacuum from the intake manifold at idle or closed throttle and the other takes over at open throttle from further up the intake when there's no vacuum in the intake manifold,so the engine is ventilated in all operating conditions.

This is exactly how the Omegas system works, just laid out differently.
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 24 September 2012, 21:31:51
EGR is doing a slightly different thing, by the way.

EGR is a connection from the exhaust manifold to the intake manifold that can open under certain conditions. It means the engine is burning a mixture of fuel, air and exhaust gases instead of just fuel and air. This lowers the temperature of combustion giving better exhaust emissions and also gives a small improvement in fuel consumption when lightly loaded.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 24 September 2012, 21:32:29
The pipes into the oil filler cap are the crankshaft breathers on this engine... They're not very effective, and Ford owners don't believe in oil changes, so you'll normally find a large buildup of very black margarine under the rocker cover. ;D

 ;D

Thanks Kevin. why circulating back in to the intake though? i asked if this was this cars version of EGR but i was told a definite no. but thats what it sounds like  ???

I can't remember exactly how it works as, thankfully, my days of maintaining that car ended when it was made a couple of feet shorter. ;D

Incidentally, it had tried to kill itself once before that when the oil got into such poor condition that one of the big ends seized and it suffered a leg out of bed (connecting rod through the side of the block leaving a fist-sized hole).
I think you'll find one of those breather pipes comes from before the throttle, I.E. air filter box or ducting, and one comes from a small jet after the throttle, i.e. the throttle body or intake manifold. It's simply a case that one pipe creates a slight vacuum from the intake manifold at idle or closed throttle and the other takes over at open throttle from further up the intake when there's no vacuum in the intake manifold,so the engine is ventilated in all operating conditions.

This is exactly how the Omegas system works, just laid out differently.

 :o :o :o :o ;D ;D ;D ;D

got to say though they're really easy to work on compared to my omega  ::)

but thanks fir that explanation.... it all makes perfect sense!!!  :y

distributor is in a weird place though, RIGHT UNDER the intake manifold - would be a bugger to get to
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 24 September 2012, 21:34:16
EGR is doing a slightly different thing, by the way.

EGR is a connection from the exhaust manifold to the intake manifold that can open under certain conditions. It means the engine is burning a mixture of fuel, air and exhaust gases instead of just fuel and air. This lowers the temperature of combustion giving better exhaust emissions and also gives a small improvement in fuel consumption when lightly loaded.

cheers mate. i knew my friends at OOF would put me on the right track  ;D :y :y :y

difficult at times trying to get all the info you need when the teachers are having to spend a lot of their time bollocking kids running round with windy guns pretending to be in Die Hard  ;D ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 24 September 2012, 21:36:41

distributor is in a weird place though, RIGHT UNDER the intake manifold - would be a bugger to get to

Yep, it's also a bugger when you have a crossflow engine on carbs and the carburettor starts leaking fuel onto the distributor (which contains sparks, of course). Just another way these engines attempt suicide. It's a good job most are now injected. ;D
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 24 September 2012, 21:37:22
Dizzies are a nightmare on them (although the Endura engine had a DIS pack) as are plugs.........right upto final production Ford still used tapered seat plugs which are nicly positioned at the front where the wet and shite sprays.

I have actualy had to bin two heads off these when plugs sheared off on removal and NOTHING would get the remains out!

Its a good job the head can be changed in an hour!  ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 24 September 2012, 21:37:55
By the way, I completely forgot to mention some more good news...... I got an ''outstanding'' on my first assignment  :) :) :) :) :) :) that H&S one I mentioned.

just toying with the idea of posting it up...... but then it may send peeps to sleep  :-\ ::) :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 24 September 2012, 21:38:25
Search on here, I and a few others have explained a few times what EGR does (might even be in the FAQ section)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 24 September 2012, 21:39:52
Search on here, I and a few others have explained a few times what EGR does (might even be in the FAQ section)

yep, should have read before i posted  ::)cheers mate  :y
Title: Re: Mechanic School Blog
Post by: Andy B on 24 September 2012, 21:48:02
............right upto final production Ford still used tapered seat plugs ....

I have actualy had to bin two heads off these when plugs sheared off on removal and NOTHING would get the remains out!
 .......

because people over tighten them  ...... too used to a crush washer under a plug.  :y :y :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 24 September 2012, 21:55:37
............right upto final production Ford still used tapered seat plugs ....

I have actualy had to bin two heads off these when plugs sheared off on removal and NOTHING would get the remains out!
 .......

because people over tighten them  ...... too used to a crush washer under a plug.  :y :y :y

And because they extended the service interval to 20K miles!

A few winters, salt the lot and the dam things rust in   ;D
Title: Re: Mechanic School Blog
Post by: Andy B on 24 September 2012, 22:20:11
.....
And because they extended the service interval to 20K miles!
 ......

 ;D ;D  I can only relate to my MKIII Cortina  ;), and that was lucky to not need something doing under the bonnet within a couple of hundred miles, let alone 20 000 miles!  ;D ;D
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 24 September 2012, 23:11:30

And because they extended the service interval to 20K miles!

A few winters, salt the lot and the dam things rust in   ;D

In practice most Fords appear to get serviced "when they stop moving". ;D
Title: Re: Mechanic School Blog
Post by: 05omegav6 on 24 September 2012, 23:53:33
Well you might as well service the thing if you've bothered to drag it to the garage when it breaks ::)
Title: Re: Mechanic School Blog
Post by: Andy B on 25 September 2012, 00:01:06
....

In practice most Fords appear to get serviced "when they stop moving". ;D

 ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 25 September 2012, 20:36:25
DAY 13:

Today saw me get in for a short day....10.45 to 16.15. Basically on Tuesdays and Wednesdays I get in late cos they have Maths and English retakes for the retards kids who didn't apply themselves fully in school. To be fair that's actually none of my group as they're all pretty smart kids. Ironically it is annoying though... I'd much rather come in and have another full day practical. Instead the lesson from 10.45 to lunch is a ''Tutorial''. Absolute 'dangle berries' if I'm brutally honest. As if this ''lesson'' wasn't pointless enough the one thing I was told I'd get from it would be proof reading of my assignments..... first assignment I asked to be proof-read was met with ''it's best if you get it read by your MV tutor as he'll know the answers''. ok. wtf!!!! grrrrr

Anyway, rant over.

We got assigned a new job today  :)

Me and my bud pulled the crank shaft out of a 1988 Astra 1.8.....unsure whether it was SOHC or DOHC as the head was mising  ??? but nevertheless we got the crank out and left the pistons in (sump off, main bearings off, big end bearings off, crank oulley off, oil pump off)
(http://i1226.photobucket.com/albums/ee402/webbybear1/day133.jpg)
unsure the name of this device that we put our crank shaft on to (crankshaft holder device perhaps?  :D ::)) but we locked the shaft in place and awaited further instructions...

We were instructed to get a micrometer....
(http://i1226.photobucket.com/albums/ee402/webbybear1/day131.jpg)
apologies for the poor pics but anyway this we were told to use to measure the main bearing shafts.... the front had a minimum thickness of 53.47mm (iirc) and the centre and rear had minimum 54.something. ours all measured at the 57mm mark... cant remember exactly what. anyhow i did learn that these bearings have shells in between to actually aid wear on the shaft bearing so if they get ttoo worn they're simply replaced. good idea!  :y

Anyway, we did a measurement report which basically consisted of noting the minimums, noting what our readings were and our reccommendations.... which in this case were that the bearings were well above minimum and could therefore be used again with no further action.

we then put the crank back, sewed up the bottom end, sump back, job done. that was basically this afternoons productivity.

there are a couple of things i'd like to mention as asides....

1.) not sure if this is something used in garages or whether its something unique to the college(s) but we have a system called ''AUTODATA''.........
(http://i1226.photobucket.com/albums/ee402/webbybear1/day132.jpg)
you click on the make, model, year, engine size and then you're brought all the technical data like torque settings, measurements, head bolt sequences, tolerances for components etc. anyone use or know of this? really rather good :)

2.) i talked yesterday about valve clearances. the trick my teacher showed me was to get the clearance to what you believe is correct. then you take the next feeler gauge up (e.g. a 0.35 if the clearance should be 0.3) and if it fits in the gap then you need to tighten down. if it doesn't fit and you have resistance or ''drag'' on the correct gauge then you're spot on  8)

3.) the hydraulic lifters should also be checked for clearance apparently between the cam lobe (its corresponding cylinder again on tdc compression).

Anyways that concludes today's lesson.

ooooh one cool thing about college.... you get free pens and condoms  ;D ;D ;D ;D
(http://i1226.photobucket.com/albums/ee402/webbybear1/day13.jpg)
will come in handy if i ever need to do the MARIGOLD test and dont have any marigolds..... definitely wont be using them for the purpose they were intended. love cars, hate s*x  ;D ;D ;D ;D ;D ;D ;D

Car Bear
Title: Re: Mechanic School Blog
Post by: henryd on 25 September 2012, 22:17:29
I use the Autodata program,very useful tool :y :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 26 September 2012, 08:03:45
As already mentioned, the feeler gauge set up does not work well on some engines including the Ford ones (there are some good alternatives). Did he tell you to apply light pressure to the push rod side of the rocker so as to remove the clearances in that part of the valve train?

Much more fun is settting the clearances on pushrod engines that need it doing when they are running (the old Nova 1.0 engines were like that)

A 1988 1.8 Vx engine will be an 8 valve although the bottom end is pretty much the same as the later 16V headed unit (which appeared in the early 90's)
Title: Re: Mechanic School Blog
Post by: Andy B on 26 September 2012, 09:17:04
....
Much more fun is settting the clearances on pushrod engines that need it doing when they are running (the old Nova 1.0 engines were like that)

.......

Same as the older CIH cam in head Vauxhall lumps before they fitted hydraulic lifters. At least the undserside would never rust after you'd done them.  ;D
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 26 September 2012, 09:32:59
Ah yes.

The hydrauilc lifter versions also needed initial setup with them running to. You used to back them off until they started to chatter and then wound the adjustment nut in a whole turn (slowly).

I had a home made cover for the timing chain for these.

The Nova 1.0 (which was also available as 1.2 in the Mk1 Astra) spilt almost no oil when setting them up, you could watch a small drop of oil flick upwards off the rocker and it landed almost where it started from!
Title: Re: Mechanic School Blog
Post by: Andy B on 26 September 2012, 11:57:47
Ah yes.

The hydrauilc lifter versions also needed initial setup with them running to. You used to back them off until they started to chatter and then wound the adjustment nut in a whole turn (slowly).


Correct! I found a 'tappet' kept coming loose after higher motorway runs. It would always quieten up when adjusted & would stay silent till the next motorway run. I eventually discovered there was a samll hairline crack in the top of the lock nut! New nut sorted it ..... infact I think I still have a brand new somewhere in my garage  ??? No idea where no though  ;D
Turning more than 360 degrees though made the car undrivable ..... apparently!  ::)

I had a home made cover for the timing chain for these.

GM made mine  ;). I just cut a hole/slot in the top of a steel 4 pot rocker cover. It was later cut in half & extended when I got a 6 pot Senator  :y
Title: Re: Mechanic School Blog
Post by: omega3000 on 26 September 2012, 19:54:45
No school today  :( ::)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 26 September 2012, 21:14:15
DAY 14...... Engine theory. Bits in red I need help with :)

Today started off well....100% correct answers for our weekly knowledge test with which I'll sum up:

Principle role of an Int. Comb. Engine: ''to take chemical energy, provide a place to heat it and turn the recipricating (linear) energy created into rotary motion which will eventually rotate the wheels''.

Piston and crankshaft indentification (easy)

Purpose of the HG: ''To provide a seal between the block and head so as not to allow combustion, oil or water to escape.

Crankshaft to camshaft rotation ratio: 2:1 (important note to self that even though the cam shaft will only have one turn to two of the crank, the cam sprocket will have twice as many teeth as the crank sprocket).... plus one full four stroke cycle equals 720o crank rotation, 3600 cam rotation.

Identification of a chain drive:
(http://i1226.photobucket.com/albums/ee402/webbybear1/chaindrive.jpg)

State the location of a mid engine.... rule of thumb: mid engine in front of rear axel, rear engine behind rear axel.

Indicate a rocker and camshaft on a Overhead Valve (pushrod engine).... camshaft at bottom near crank which pushes push rod up and that in turn pushes the rocker (located at the top) downwards to open the valve.

And some other stuff that was easy that I shan't bother to note  ::)

Anyhow.... I mentioned that it went well. which it did. then it got hard and confusing  :'( although on reflection I think i get it :)

Ok firstly we labelled up the exact parts of a crankshaft and i labelled up this google image which shows the different parts:
(http://i1226.photobucket.com/albums/ee402/webbybear1/crankshaft21.jpg)
one really interesting thing i didnt realise until today was that the balance weights have the holes in them for literally that reason...balancing... like you'd add weight to the light area of a wheel to balance it, the balance weight is drilled of metal to balance it  :)

Ok, here's where it gets tricky....

How torque is produced in the engine....
now i qualified with the teacher that the only place in the engine where torque was produced was from the pistons. but having said that there are other areas that torque is used, obviously one we all know: the tightness of nuts and bolts using a torque wrench. however this discussion centred around engine torque....

ok, so torque is twisting force. to calculate torque it force X radius. SO
the spark occurs at the very end of the compression cycle, 10o before the piston is at TDC. Rapid burning occurs for 20o so when the piston reaches 10o PAST TDC it produces it's maximum force because there's maximum cylinder pressure and this then has the effect of shooting the piston down. NB, this pushing/shooting force could not happen at TDC because the radius would be 0o and therefore no leverage which is what you need to produce torque.
To measure the radius is where it gets dfficult (for me anyway).... it's easy with a torque wrench because when it's used at 90o to what it's tightening the radius (or leverage) is simply the length of the torque wrench  :y
HOWEVER below is how to work out the radius with regards to the crank and pistons (i've drawn this so sorry if it's a bit, errrrm, shite lol:
(http://i1226.photobucket.com/albums/ee402/webbybear1/radius.png)

NEXT: VALVE SPRINGS

to sum up the cam operates the spring and allows it to shut. the spring keeps it closed and holds the valve shut until the next time the cam opens it.

Surging/Resonating: this is vibration created (at certain engine speeds) parellel to the valve guide. is this linear (up and down) vibration or side to side vibration?  :-\

most common spring is the helical coil spring as they're easier to fit compared to hairpin springs due to them being smaller and fitting in the tight space available:
(http://i1226.photobucket.com/albums/ee402/webbybear1/valvesprings.jpg)

ways manufacturers deal with resonating is to make the spring more tightly wound... less room to vibrate.
and also two springs fitted in to one really? why would this work? didnt understand the explanation really  :'(

Anyway that concludes today's theory. I'm not in again until Monday but I have been given some stuff to research which I'll add to the group for discussion :)

Title: Re: Mechanic School Blog
Post by: Webby the Bear on 26 September 2012, 21:15:00
No school today  :( ::)

was typing steve  ::) :P :P :P ;D ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 26 September 2012, 21:23:37
Resonation is in the line of the valve (it cant occur at a right angle due to the valve guide).

Simple physics, a spring with a mass will have a resonating frequency which may be in the engine operating range ( e.g a specific rpm).

Add a second smaller spring inside the main one and design it so that it resonates at a different frequency and when one of them resonates, the other wont and hence you overcome the issue.

Or make the springs stronger and design them so they only resonate at very high rpms beyond the engine operating range, this is not good for pushrod and rocker engines as it results in larger components being needed (stronger) which increases the valve train weight.....which is not good as it limits the upper rpm range....thats a major advantage of OHC....lighter valve train  :y

Not totaly conviced on your torque talk...its the crank that converts a linear motion into a rotational one and hence its the crank where the torque is produced.
Title: Re: Mechanic School Blog
Post by: Andy B on 26 September 2012, 21:36:35
.....
 ..... the spring keeps it closed and holds the valve shut until the next time the cam opens it. ....

Unless it's a Ducati & the valves are desmodromic  ;) ;) ;) ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 26 September 2012, 21:39:44
Resonation is in the line of the valve (it cant occur at a right angle due to the valve guide).

Simple physics, a spring with a mass will have a resonating frequency which may be in the engine operating range ( e.g a specific rpm).

Add a second smaller spring inside the main one and design it so that it resonates at a different frequency and when one of them resonates, the other wont and hence you overcome the issue.

Or make the springs stronger and design them so they only resonate at very high rpms beyond the engine operating range, this is not good for pushrod and rocker engines as it results in larger components being needed (stronger) which increases the valve train weight.....which is not good as it limits the upper rpm range....thats a major advantage of OHC....lighter valve train  :y

Not totaly conviced on your torque talk...its the crank that converts a linear motion into a rotational one and hence its the crank where the torque is produced.

that makes sense re the resonating and the smaller spring inside the bigger one. however one thing i've obviously missed which i should have asked...... what's the actual problem with resonating? noise? worn parts? soz should have asked really.

as for the torque talk. as far as i know, yes, the crank is where the torque is ''given'' to the drive shaft, but its what happens in the combustion chamber and the acts and forces on the pistons that sends that power...... or have i got confused with the question?  ::) ;D
Title: Re: Mechanic School Blog
Post by: Manual Elite V6 on 26 September 2012, 21:52:50
Resonation is in the line of the valve (it cant occur at a right angle due to the valve guide).

Simple physics, a spring with a mass will have a resonating frequency which may be in the engine operating range ( e.g a specific rpm).

Add a second smaller spring inside the main one and design it so that it resonates at a different frequency and when one of them resonates, the other wont and hence you overcome the issue.

Or make the springs stronger and design them so they only resonate at very high rpms beyond the engine operating range, this is not good for pushrod and rocker engines as it results in larger components being needed (stronger) which increases the valve train weight.....which is not good as it limits the upper rpm range....thats a major advantage of OHC....lighter valve train  :y

Not totaly conviced on your torque talk...its the crank that converts a linear motion into a rotational one and hence its the crank where the torque is produced.

that makes sense re the resonating and the smaller spring inside the bigger one. however one thing i've obviously missed which i should have asked...... what's the actual problem with resonating? noise? worn parts? soz should have asked really.

as for the torque talk. as far as i know, yes, the crank is where the torque is ''given'' to the drive shaft, but its what happens in the combustion chamber and the acts and forces on the pistons that sends that power...... or have i got confused with the question?  ::) ;D

If I remember correctly when the springs reach a certain speed and are resonating at quite a high frequency the valve is in a sense just floating as the spring isn't making contact with the valves which eventually leads to the sudden contact when the resonance stops, which causes the valve to crash into the cam.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 26 September 2012, 21:58:26
Resonation is in the line of the valve (it cant occur at a right angle due to the valve guide).

Simple physics, a spring with a mass will have a resonating frequency which may be in the engine operating range ( e.g a specific rpm).

Add a second smaller spring inside the main one and design it so that it resonates at a different frequency and when one of them resonates, the other wont and hence you overcome the issue.

Or make the springs stronger and design them so they only resonate at very high rpms beyond the engine operating range, this is not good for pushrod and rocker engines as it results in larger components being needed (stronger) which increases the valve train weight.....which is not good as it limits the upper rpm range....thats a major advantage of OHC....lighter valve train  :y

Not totaly conviced on your torque talk...its the crank that converts a linear motion into a rotational one and hence its the crank where the torque is produced.

that makes sense re the resonating and the smaller spring inside the bigger one. however one thing i've obviously missed which i should have asked...... what's the actual problem with resonating? noise? worn parts? soz should have asked really.

as for the torque talk. as far as i know, yes, the crank is where the torque is ''given'' to the drive shaft, but its what happens in the combustion chamber and the acts and forces on the pistons that sends that power...... or have i got confused with the question?  ::) ;D

If I remember correctly when the springs reach a certain speed and are resonating at quite a high frequency the valve is in a sense just floating as the spring isn't making contact with the valves which eventually leads to the sudden contact when the resonance stops, which causes the valve to crash into the cam.

that makes sense mate... and just thinking aloud, i imagine that if the valve is floating like that then it could in theory be open or closed when its not supposed to be hence affecting the 4 stroke cycle. perhaps  :-\
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 27 September 2012, 08:08:54
Exactly, if the valve resonates then it does not close (it will still fully open as its being forced open but it relies on the spring to close it).

Interestingly, cams and psrung valves may weel dissappear soon, I was observing a Sulzer marine engine the other day with directly actuated valves.....i.e. electro-hydraulic.

This gives infinate timing, lift and duration control  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 September 2012, 08:36:11
Haha don't boggle my mind Mark, i can only take so much info  ;D ;D

Title: Re: Mechanic School Blog
Post by: Andy B on 27 September 2012, 09:00:37
..... marine engine the other day with directly actuated valves.....i.e. electro-hydraulic.

This gives infinate timing, lift and duration control  :y

I'm seen similar ideas before (on paper though & not in the metal) ...... It never seems to make it to the road though  :-\
Title: Re: Mechanic School Blog
Post by: albitz on 27 September 2012, 09:49:56
Pretty sure F1 cars have a similar setup.

Edit.
http://scarbsf1.com/valves.html
Title: Re: Mechanic School Blog
Post by: f3nt0n on 28 September 2012, 20:08:03
I am ABSOLUTELY LOVING this thread. My foster parents owned a garage when I lived with them 30 yrs ago and I spent a lot of time there with my fosterdad. This stuff is exactly what he taught me when I decided to take apart broken old cars and put them back together again (for profit!) including minis, a jensen-healy, a renault 4 (bought for £250 with a blown head gasket (engine out jobbie, royal pain in the arse) -£75 for HG kit - sold it for £900! PROPER PROFIT in that old motor!), an mgb and a Rover p600. Incidentally, I absolutely loved working on the Austin "A" series engine, because it was so lovely and simple!

Thanks Web and looking forward to more...
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 28 September 2012, 22:23:35
glad you're enjoying it mate. Thanks for the feedback. It's great on here too cos there's so many knowledgeable folk on here to help out and chip in. I actually have a load of stuff ive got to self study so am hoping to give another update tomorrow :-) cheers mate :-)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 01 October 2012, 21:27:44
Week 5 begins.

Evening gents, help/advice needed in red please  ;D

Well today had the potential to be interesting until the entire class (minus myself) decided they were going to dick about like idiots all day and not get on with the work  >:(
I find the guys mostly funny but there's overkill and they went past that today and the teacher saw red. Anyways.....

I did a cambelt on a SOHC Renault engine (Megane or clit, not sure which...). Well I don't think I've ever done something so simple....... Crank notch @ 6 o'clock. Cam sprocket @ 12 o'clock. Tensioner off. Belt off. We did some other stuff to the head that I'd already done and gone through on here (valve springs out, lapping in the valves with the grinding paste, reattach the head etc etc).
Anyway, cam sprocket and crank sprocket both at their respective timing notches/marks. belt on, feed tight up the right hand side (as you look at it) belt over the cam sprocket, tensioner back in, tighten tensioner up. PIECE OF P...!

So that was enjoyable and half way through we were shown compression testing  :) :) :) :) :) :)
Real simple..... if you got a 4 pot you would do 4 ''Dry'' tests and 4 ''Wet'' tests. I'll explain.

1.) Isolate the fuel system... pull fuel injectors out or simply pull the Fuel Pump fuse out  :y
2.) Isolate the spark... pull the HT leads out, take the spark plugs out and disconnect the distributor/coilpack.
3.) Break out this bad boy...
(http://i1226.photobucket.com/albums/ee402/webbybear1/compressiontester.jpg)
you fix it to the correct attachment that's the same size as your spark plugs and then screw it in to pot one for the first of the ''Dry'' tests. Turn engine over a few times and the dial above will score your first reading. Repeat for 3 other pots.
4.) Time for ''Wet'' testing. Let's keep it simple. Pot 1 we'll imagine we got a dry reading of 165. We then pour some oil down the spark plug well. this will cover the top of the piston. plug in our compression tester. Turn engine over and record our reading. if its the same or only slightly above our initial ''dry'' test reading then our pot is good for compression. if on our wet test we get a reading thats 40+ above our initial dry test reading (so a reading of 205 upwards) then our pot is losing compression.....
We know this because the oil we poured in has sealed where our compression leak is and hence given us a higher reading. If we had no compression leak in the first place the oil would make no (or very little difference).

Sadly i'd only just got through my dry test on pot 3 when my class decided to turn in to a load of immature retards and we were all told to pack away early in preperation for a 30 minute bollocking!  >:( seriously i really dont see why i should have to pack up what i'm doing cos some little tw*ts can't stop honking the car's horns!!!  i and a few others genuinely want to learn!!! >:( >:( >:( >:( >:(

Rant over. Actually no it's not...

The tutor did also go through a ''Leak Down Test''. Again this was doomed from the off..... there's two leak down test gauges available. Both used by some moronic children who used them without setting them back to zero before reusing. this broke them  :( this is simply tested by not plugging it in and getting a reading from the fresh air.... ours in the fresh air was saying we had no leak  ::) ;D
So I presume we'll have to wait for a new one to be ordered  ::)

If you're wondering what the difference is between a compression test and a leak down test..... ask someone else cos i wasn't told! lol ;) i can't understand what the difference is because the compression test will measure air pressure in the cylinder and you perform the wet test to see if there's leaks..... the leak down test will also find leaks. at a guess i'd say the leak down test would be more foolproof. Anyone care to clarify?

So if this day wasn't a tad mental anyway, halfway through the tutor's rant he chucks in a load of formulas. now i'm sad that he did this. i'm not the best at maths  :'( and i like to take my time when given an equation.

HOWEVER. i'm going to post this now and show this as ''today's lesson''..... and expect another post in a few minutes about cylinder formulas and you can hopefully tell me if i've managed to grasp it.  :y

oooooh one last quick thing..... We measured a cylinder head for warping  8) so easy...... get a flat edge, place it on the head (combustion chamber side).... can you get the smallest feeler gauge in between the head and the flat edge tool.... yes? you hae warpage and it needs to be machined. no? your head is not warped. proceed  :y
Title: Re: Mechanic School Blog
Post by: omega3000 on 01 October 2012, 22:11:22
Nice work , shame about those knuckle heads spoiling it  >:(

(http://i15.photobucket.com/albums/a384/themarbleintheoatmeal/smilies/watchdrama8jm.gif)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 01 October 2012, 22:35:36
Mechanic School Blog After Hours  ::)

CYLINDER FORMULAS & VOLUMES

SWEPT VOLUME a.k.a ''STROKE'' VOLUME a.k.a DISPLACEMENT a.k.a ENGINE LITRE SIZE
This quite simply is the volume covered by the cylinder from it's upper most point (TDC) to it's lowest most point (BDC):
(http://i1226.photobucket.com/albums/ee402/webbybear1/pistondiagram.png)
Swept volume formula is: Pi X radius squared X the stroke.
EXAMPLE: if the diameter (or bore) of your cylinder is 80mm and your stroke is 70mm the calculation would be: 3.14159265359 X 16cm X 7cm = 352cm3.............X4 cylinders = 1407cc (1.4L Engine  :y)

CLEARANCE VOLUME (The volume of the Combustion Chamber)
This, again quite simply, is the area from TDC upwards which is basically the combustion chamber. Difficult to measure when you think that usually the combustion chamber is hemospherical (if thats even correct  :-\ ::))
See this diagram and the crude white marked out area with the purple star.... its late, ok?  ::) ;D
(http://i1226.photobucket.com/albums/ee402/webbybear1/pistondiagram-clearancevol.png)
Clearance volume formula is: Swept Volume / Compression Ratio - 1.
EXAMPLE: From the example before... one cylinder = 352cm3 / 8:1 - 1 = 7. 352/7 = 50.285cm3

COMPRESSION RATIO
This is the combustion chamber volume expressed as a ratio compared to the swept volume.
Compression Ratio Formula is: Swept Volume + Clearance Volume / Clearance Volume
EXAMPLE: Our pot on this shite 1.4L engine is has a swept volume of 352cm3 + 50.255cm3 = 402.26cm3 / 50.285cm3 = 7.999........... Compression Ratio of 8:1  :y

Right guys, this is seriously enough maths for today. I hope I've got all the above correct but if I haven't please do correct me... I need to learn.

I'm a bit pee'd off I've had to research this myself when I should have had it taught to me in class but due to the stupidity of what turned out to be the majority  ::)

Well that is rant over.

Hope you enjoyed the detail but I doubt it as I know it's a bit... errrrm.... tedious  ;D ;D ;D ;D

over and out until tomorrow my dawgs ;)

Car Bear.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 01 October 2012, 22:59:48
Sod it, one final math problem we had to work out... couldn't do it in class as too many distractions but the question is this:

Four cylinder engine has a bore diameter of 80mm and a stroke of 70mm. Calculate the Compression Ratio if clearance volume is 40cm3

SO.

I firstly work out my SV.... 3.14 X 16cm X 7cm = 351.68

I add my CV - 351.68 + 40 = 391.68

Divide this by the CV = 9.792................CR = 9.79:1
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 02 October 2012, 08:13:15
A few observations on the compression testing.

1) The throttle needs to be fully open when testing

2) The oil trick is actualy not that great, to often the oil gets nowhere near the rings, particularly on modern multivalve engines and it just sits on the top of the pistons (as many or pocketed or slightly dished). The result is an increase in CR any way as the clearance volume. Also, adding only a few drops of oil equals a cc!

Your CR calc gives you static CR, dynamic CR will be different and will be higher thanks to scavenging or forced induction.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 05 October 2012, 18:41:51
A few observations on the compression testing.

1) The throttle needs to be fully open when testing

2) The oil trick is actualy not that great, to often the oil gets nowhere near the rings, particularly on modern multivalve engines and it just sits on the top of the pistons (as many or pocketed or slightly dished). The result is an increase in CR any way as the clearance volume. Also, adding only a few drops of oil equals a cc!

Your CR calc gives you static CR, dynamic CR will be different and will be higher thanks to scavenging or forced induction.

Mark, thanks for responding on this. Also, yes defo should have mentioned to have the throttle fully open. And certainly the teacher definitely treated the compression test as a 'Quick Test'' that should be backed up by a leakage test.

Dynamic CR  :o :o :o :o Thought I'd cracked it!  ::) :D I'll look in to that, or better still get my tutor to fully explain it as punishment for pulling me in when the kids got in trouble!  :y

Got quite a big update to do but I've been poorly this week (still went to school of course)  :'(

Chillin' tonight so gonna pop a top on a few beers and spend all evening on here updating  :y
I'll
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 09 October 2012, 00:00:22
Last Tuesday/Wednesday and today...

Evening chaps, very sorry I didn't update as intended to last week... ended up getting drunk on Friday night instead  :)

Well it's been a busy week. More theory to go through and also my first engine practical assessment today  :y

Ok so last weeks' lessons consisted of the following:

Although I said I couldn't do a leak down test because the dials were broken I still managed to sneak a pic of the demo before we found out it was bust  ::)
(http://i1226.photobucket.com/albums/ee402/webbybear1/fiestaleakagetest.jpg)
The dial on the right shows the leakage and it has green, amber and red to show whether it's good, bad or ugly  ;D

''Poppet'' valve the most common type of valve...
(http://i1226.photobucket.com/albums/ee402/webbybear1/poppetvalves.jpg)
The seat (the bit that is angled from the stem) is machined to an angle between 30o and 45o so they fit or ''seat'' nicely into the head so it seals. the valve seat in the head is angled slightly more to allow for expansion.... gets hot in that there combustion chamber  :y
Exhaust valves are smaller than the inlets and I believe (although I don't have the exact explanation written down weirdly) it's something to do with the exhaust temperature. Maybe someone could clarify?  :)

So to break down the components of the valve....
(http://i1226.photobucket.com/albums/ee402/webbybear1/valvediagram.jpg)
the valve itself obviously has a valve tip, the spring fixing (where those little collets sit and keep the spring in place), the valve stem, the valve head (where the stem starts to angle, the seating which has the 30-45o angle to fit in to the head nicely and the face which i think is the flat bottom.
another reason why the valve must seat correctly and securely is because the combustion chamber needs to be able to dissipate the heat it creates. if the seating is too shallow or doesnt fit correctly you will get burned out valves.... expensive to replace i imagine!
finally on valves you have the spring which the collar goes over, compress that down, fit the collets, release compressor=one nicely fitted valve  :y

moving on from valves as that part we learned kinda got very dull after 2 hours of talking about it!...... i aso learned that the crankshaft has a ''woodruf key''. this is like a notch or groove that slots in to the first main journal (main bearing) and keeps the crank pulley in place.....
(http://i1226.photobucket.com/albums/ee402/webbybear1/woodrufkey.jpg)

a quick note about the piston....
through the centre of it is a gudgeon pin. this allows the con. rod to rotate within the pistin. at the top of the con rod is the little end bearing (as its smaller) and on the other end is the................ thats right, big end bearing and is fitted to the crank pin via the big end bearing cap. worth noting that on the inside of the big end bearing and the big end bearing cap are two semi-circle shell type things... simply there so that they take the wearing and can be replaced and not the big end/cap themselves. simple but effective ;)
also if you cut the con rod in half it would be 'H' shaped. this is for extra strength. a square shape could buckle  :y

a quick word about camshafts....
DID YOU KNOW that they are slightly offset to their corresponding follower? this is so that when it opens the valve not only does it simply open and close but also turns the valve as it does so....this helps get rid of the heat more effectively.... think of air ''swirling'' if you will.  :y

ok, i do have some more stuff to go through but i am beat for now. got some cool assessment pics to show you though when my phone wants to send e mails again  >:(

ta ta for now  :y
Title: Re: Mechanic School Blog
Post by: albitz on 09 October 2012, 00:11:33
Great stuff again webby.Be aware though that not all engines are of the same design.For example,not all crank pulleys have a woodruff key,not all bearings are shell type bearings etc.Expensive,highly tuned engines (particularily in bikes) will have needle roller bearings in the small and big end bearings. And then you have the Ducati Desmodromic valve system which has no valve springs.Springs are closed by mechanical means as well as opened.No valve spring bounce or coil binding to worry about,so engine can rev higher.
 Your learning fast though mate.This stuff will stand you in good stead for years to come,until you get to my age. Then everytime you learn one thing you forget three others. :'( ;D
Title: Re: Mechanic School Blog
Post by: Andy B on 09 October 2012, 00:21:37
......
For example,not all crank pulleys have a woodruff key, .....

The diseasal Astra I had was as you say. Cam pulley was just on a taper fit, and cam timing really needed a separate bit of kit that used one of the cam lobes to time it up. Glad I didn't remove the nut on the end .......as I very nearly did.  ::)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 09 October 2012, 09:55:30
Also, many modern engines dont have the camshaft lobe off set (or a raised side profile as per the Rover V8) to rotate the follower as they use better hardening and oil is MUCH better so its not required.

Also valve seat angles, most if not all modern engines will have multiple angles ground onto the seat to support better gas flow.

Exhaust valve size is a compromise, you only have a limited space available within the combustion chamber for valves and its harder to get air/fuel in than exhaust gases out (exhaust gases are expanding as the exhaust valve opens before BDC so they force themselves out plus the piston will push them out as it rises on the exhaust stroke) so they can be made smaller so you can make the inlets bigger (as on a NA vehicle the inlet will be at a vaccum) which is where you want the biggest valves you can get
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 09 October 2012, 12:09:24
Thanks for the input chaps. Very useful as ever!!!

Ok, so carrying on from last night.....

Valve lead, lag and overlap....

LEAD = When a valve opens shortly before the next stroke. An example of this would be the inlet opening at the end of the exhaust stroke ready for the induction stroke.

LAG = When a valve finishes closing shortly after the next stroke has started. I think an example of this would be the exhaust shutting shortly after induction.... but I'm a tad unsure. We have looked briefly at valve timing diagrams and I'm going to be honest it's a bit confusing  ;D but we're going to look more in depth at these later so sorry if I got this one wrong.

OVERLAP = When two valves are open at the same time. An example is the start of the induction stroke  :y

There's other stuff as well but I need to upload piccies tonight  :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 09 October 2012, 13:18:43
Some basic info on here about about valve timing etc here:

Valves

http://www.omegaowners.com/forum/index.php?topic=90472.0 (http://www.omegaowners.com/forum/index.php?topic=90472.0)

Valve Timing

http://www.omegaowners.com/forum/index.php?topic=90474.0 (http://www.omegaowners.com/forum/index.php?topic=90474.0)

For completeness, compresion ratio:

http://www.omegaowners.com/forum/index.php?topic=90473.0 (http://www.omegaowners.com/forum/index.php?topic=90473.0)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 09 October 2012, 21:19:51
That's really useful, Mark! Really bloody useful in fact! We hardly touched the surface last week but I know we're going to get in depth with valve timing. it certainly makes sense, especially why the inlet is allowed to open before TDC on the exhauset stroke as you say having the overlap will create a vacuum which, when you're wanting to get your mixture in in however many miliseconds it is then i suppose every little aid helps the overall process massively  :y :y :y :y :y so thanks for that!

well, hopefully youll be pleased to know i finished my first assessment and although its still being marked the tutor commented that my work was very impressive!  8) 8) 8) 8)

in short over the last few weeks, as you've seen from the photos, we've had a load of different engine jobs that we've practised and for the assessment we simply had to choose one. me and my buddy chose removing head, whipping valves out, lapping them in, putting the valves back in and refiting the head and timing it up correctly.

i shan't go through it all as although it was a different engine i've already highlighted the job with pics previously. HOWEVER, i did get this pic which i think may interest you.....
(http://i1226.photobucket.com/albums/ee402/webbybear1/engassess.jpg)
this engine is a 1991 Ford Escort 1.8 DOHC.
Firstly i'll highlight that me and my buddy did make one mistake and that was we assumed something  ::) there was a notch on the crank and every other engine we've worked on has been at TDC when the notch is at 6 o'clock. Sadly for us it should've been at 5 o'clock  ::) ::) ::) ::) ::) but only ourselves to blame as we should've double checked..... luckily it was the only mistake we made  8)
the very interesting thing about this engine (or interesting to me at least) is it's the first engine that's required the use of a camshaft alignment tool (all other engines in the workshop have simply used timing marks...very crude). the photo shows the back of the engine and if you look at the back of the cam shafts youll note two indents that when they're at the correct time you can slot the alignment tool nicely in and it fits perfectly. with the crank at 5 o'clock this bad boy is timed up  8)

OK next up the cam lobe...
(http://i1226.photobucket.com/albums/ee402/webbybear1/CAMDIAGRAM.jpg)
pretty straightforward. the longer the nose the longer the valves stay open for.... i suppose thats why they say the bump stick is the heart of the engine as its performance will change the performance of the car.

next, firing orders....
we learned very little about this but what i do know is that the reason the foring order appears ''random'' (instead of just 1234) is to balance out the power strokes across the engine.
Four pot enginges have one of only two possible firing orders:
1342   or    1243
i still dont get why you couldnt have 1324  :-\ in my mind thats the most even order
In line 6 cylinder engines can only have the fllowing:
145632, 142635, 132645 or 135642.
as mentioned before sadly we didnt delve in to this so thats the only info i have..... feel free to add as appropriate  :y

lastly pistons and the combustion chamber.....
i've mentioned the crown (very top), the rings (two compression rings and one oil ring with gaps at 180o to avoid leakage, the skirt, the gudgeon pin. but i would also like to add that the combustion chamber shapes are designed to help to burn the mixture and also create a swirly vacuum for the mixture and exhaust gases. moving air is hard so agan every little helps!  :y

Anyway thats it until tomorrow. hope youve enjoyed so far  :y
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 09 October 2012, 22:23:06
Thought it looked familiar.  ;)

http://www.omegaowners.com/forum/index.php?topic=41484.msg627149#msg627149 (http://www.omegaowners.com/forum/index.php?topic=41484.msg627149#msg627149)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 10 October 2012, 10:39:54
Small block GM engines use the same cam timing method (they are chain based) e.g. the 1.0, 1.2 and 1.4.

I have a few medium 6 cylinder diesels to re-build shortly (11 plus ltres) having just finished a Land Rover 2.5 diesel head gasket and a BSD444 diesel engine job. Once you understand the basics then they are all actualy surprisingly similar.

If you ever want to see a real engine then pop up to Nottingham!

You should also now have enough understanding to start thinking what certain engine management sensors do....e.g. crank sensor and cam sensor.
Title: Re: Mechanic School Blog
Post by: Andy B on 10 October 2012, 12:07:02
....
You should also now have enough understanding to start thinking what certain engine management sensors do....e.g. crank sensor and cam sensor.

Sense the crank & sense the cam ........  ::) ::) ::)
Title: Re: Mechanic School Blog
Post by: TheBoy on 10 October 2012, 18:03:53
....
You should also now have enough understanding to start thinking what certain engine management sensors do....e.g. crank sensor and cam sensor.

Sense the crank & sense the cam ........  ::) ::) ::)
But why ;)
Title: Re: Mechanic School Blog
Post by: ozzycat on 10 October 2012, 22:20:02
 :y :y this is a brilliant  thread webby brings back alot of memories :y :y :y :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 11 October 2012, 08:09:32
One question.....how often have you used a torque wrench on engine re-assembly and on what bolts/nuts.......?
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 October 2012, 19:21:31
One question.....how often have you used a torque wrench on engine re-assembly and on what bolts/nuts.......?

Well prior to the course I only used my own torque wrench on the wheel nuts. however since the course i've used it on everything when putting the engine back..

e.g. on this assessment which was just top end we had torques for:

inlet manifold
exhaust manifold
coil pack retaining bolts
head bolts (inc. head correct tightening sequence)
cam shafts shells (inc. tightening sequence)
valve cover

cant think of any more we used.

the head bolts were torqued in stages... however cos they're stretch bolts and they've been undone/re-tightened many times we just did the first two stages and missed out the final ''angle tightening''.

 :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 October 2012, 19:22:39
ooooh forgot we also had a torque for the timing belt tensioner bolt  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 October 2012, 19:30:18
Thought it looked familiar.  ;)

http://www.omegaowners.com/forum/index.php?topic=41484.msg627149#msg627149 (http://www.omegaowners.com/forum/index.php?topic=41484.msg627149#msg627149)

haha awesome!  :y :y :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 October 2012, 19:40:02
Small block GM engines use the same cam timing method (they are chain based) e.g. the 1.0, 1.2 and 1.4.

I have a few medium 6 cylinder diesels to re-build shortly (11 plus ltres) having just finished a Land Rover 2.5 diesel head gasket and a BSD444 diesel engine job. Once you understand the basics then they are all actualy surprisingly similar.

If you ever want to see a real engine then pop up to Nottingham!

You should also now have enough understanding to start thinking what certain engine management sensors do....e.g. crank sensor and cam sensor.

cheers mark, very helpful as ever! maybe we could combine it with you supervising my cambelt change too if thats possible... ill pay you of course. just if i go to TB near me, when i get it wrong and he has to step in he may put his back out again and i dont want that on my conscience :-X ;D  :y

i tell you what i'm really interested in also.... after finding out the RPM facts and that at a constant 3k RPM the piston would be going up and down 100 times a second..... is there any way i wonder of being able to view that?  :-\ i imagine if it was possible it would simply be a blur?

while i'm thinking out loud also....... with valve overlapping......say for example where both valves are open at the end of the exhaust stroke tyhrough to start of induction...... if two valves are open at the same time why then doesnt the piston come in contact with the valves like say when a cambelt tensioner goes and the engine lunches on itself ???

cheers guys  :y :y :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 October 2012, 19:45:27
:y :y this is a brilliant  thread webby brings back alot of memories :y :y :y :y

thanks for the feedback mate.... nice to hear its of interest and i aint just boring folk  ;D ;D ;D :y :y :y
Title: Re: Mechanic School Blog
Post by: albitz on 11 October 2012, 19:48:34
The valves may be open to some extent at the same time,but they wont be open at TDC. ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 October 2012, 19:51:29
The valves may be open to some extent at the same time,but they wont be open at TDC. ;)

Cheers Albs  :y :y :y
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 11 October 2012, 20:11:12
cheers mark, very helpful as ever! maybe we could combine it with you supervising my cambelt change too if thats possible... ill pay you of course. just if i go to TB near me, when i get it wrong and he has to step in he may put his back out again and i dont want that on my conscience :-X ;D  :y

Naah.

I reckon he'll just look up from his cup of tea and say "It's not my effing car". ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 October 2012, 20:14:53
cheers mark, very helpful as ever! maybe we could combine it with you supervising my cambelt change too if thats possible... ill pay you of course. just if i go to TB near me, when i get it wrong and he has to step in he may put his back out again and i dont want that on my conscience :-X ;D  :y

Naah.

I reckon he'll just look up from his cup of tea and say "It's not my effing car". ;)

 ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: Lazydocker on 11 October 2012, 20:21:42
cheers mark, very helpful as ever! maybe we could combine it with you supervising my cambelt change too if thats possible... ill pay you of course. just if i go to TB near me, when i get it wrong and he has to step in he may put his back out again and i dont want that on my conscience :-X ;D  :y

Naah.

I reckon he'll just look up from his cup of tea and say "It's not my effing car". ;)

I can't believe he would ever utter those words :-X ::)

Or... "Keep him busy, I just broke something!" ::) ;D
Title: Re: Mechanic School Blog
Post by: TheBoy on 11 October 2012, 21:20:32
cheers mark, very helpful as ever! maybe we could combine it with you supervising my cambelt change too if thats possible... ill pay you of course. just if i go to TB near me, when i get it wrong and he has to step in he may put his back out again and i dont want that on my conscience :-X ;D  :y

Naah.

I reckon he'll just look up from his cup of tea and say "It's not my effing car". ;)
Well, its not, is it ::)
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 11 October 2012, 22:20:35
The valves may be open to some extent at the same time,but they wont be open at TDC. ;)

Not on the power stroke but they will between exhaust and intake. Gas moving down the exhaust scavenges the cylinder much more effectively if the intake valve is already opening, and this also helps to accelerate the intake charge before the piston starts to move down the cylinder.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 October 2012, 22:22:54
The valves may be open to some extent at the same time,but they wont be open at TDC. ;)

Not on the power stroke but they will between exhaust and intake. Gas moving down the exhaust scavenges the cylinder much more effectively if the intake valve is already opening, and this also helps to accelerate the intake charge before the piston starts to move down the cylinder.

Thanks Kev so how come they dont hit the piston between the E and I strokes?  :y
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 11 October 2012, 22:28:47
The valves may be open to some extent at the same time,but they wont be open at TDC. ;)

Not on the power stroke but they will between exhaust and intake. Gas moving down the exhaust scavenges the cylinder much more effectively if the intake valve is already opening, and this also helps to accelerate the intake charge before the piston starts to move down the cylinder.

Thanks Kev so how come they dont hit the piston between the E and I strokes?  :y

Well, they're not fully open. Exhaust valve is closing and intake valve is opening at this time, and the clearance between valves and piston is carefully worked out. ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 October 2012, 22:30:59
The valves may be open to some extent at the same time,but they wont be open at TDC. ;)

Not on the power stroke but they will between exhaust and intake. Gas moving down the exhaust scavenges the cylinder much more effectively if the intake valve is already opening, and this also helps to accelerate the intake charge before the piston starts to move down the cylinder.

Thanks Kev so how come they dont hit the piston between the E and I strokes?  :y

Well, they're not fully open. Exhaust valve is closing and intake valve is opening at this time, and the clearance between valves and piston is carefully worked out. ;)

cheers mate, was just wondering  :y :y :y
Title: Re: Mechanic School Blog
Post by: aaronjb on 11 October 2012, 22:32:48
The valves may be open to some extent at the same time,but they wont be open at TDC. ;)

Not on the power stroke but they will between exhaust and intake. Gas moving down the exhaust scavenges the cylinder much more effectively if the intake valve is already opening, and this also helps to accelerate the intake charge before the piston starts to move down the cylinder.

Thanks Kev so how come they dont hit the piston between the E and I strokes?  :y

Well, they're not fully open. Exhaust valve is closing and intake valve is opening at this time, and the clearance between valves and piston is carefully worked out. ;)

Or if you're feeling ghetto, checked with some plasticine..  :-[
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 11 October 2012, 22:35:01
Or if you're feeling ghetto, checked with some plasticine..  :-[

True. :D

Or the seat of the pants if you're running hydraulic tappets. ::)
Title: Re: Mechanic School Blog
Post by: aaronjb on 11 October 2012, 23:38:18
Or if you're feeling ghetto, checked with some plasticine..  :-[

True. :D

Or the seat of the pants if you're running hydraulic tappets. ::)

Indeed, it gets expensive if you need to buy two sets just to fill some with wax.. ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 17 October 2012, 12:39:50
afternoon chaps. Got some great stuff to share with the class. Going for a curry with Martin42 tonight as the northampton branch of OOF ha ha anyone in the area wants to go let me know. Anyway prob wont get an update chance today but will do tomorrow. Moved on to diesel today but before all that i have the interesting pug exhaust to go through. Lol it Wasnt pretty ha ha prob update tomorrow :-)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 21 October 2012, 15:35:06
Afternoon fellas...

Well bit late with the update for this weeks' blog but as Im now on half term for two weeks  8) i didnt see the point in rushing  :y
However, there's a lot to cover. so let's start at the beginning :)

SPARK PLUG WEAR:
Image of a spark plug with normal wear... brown or grey colouration at firing end:
(http://i1226.photobucket.com/albums/ee402/webbybear1/sp1-1.jpg)

Image of a spark plug with white ''crusty'' deposits at firing end.... plugs have overheated probably due to use of plug with incorrect heat range:
(http://i1226.photobucket.com/albums/ee402/webbybear1/sp2.jpg)

Image of spark plug with carbon fouling due to over rich fuel mixture... any idea why the mixture could get over-rich???
(http://i1226.photobucket.com/albums/ee402/webbybear1/sp3.jpg)

Image of spark plug with oil fouling.... due to worn bores and/or piston rings or worn valve guides. this also can occur temporarily during the running in period:
(http://i1226.photobucket.com/albums/ee402/webbybear1/sp4.jpg)

Image of spark plug with blistered white deposits (difficult to differentiate between this and the crusty one in my opinion) ...... caused by worn valve guides, excessive use of upper cylinder lubricant, or idling for long periods.
(http://i1226.photobucket.com/albums/ee402/webbybear1/sp5.jpg)

Finally on spark plugs....
a SP that is worn through age/use will have an increasingly larger gap. the effect this will have...
weak spark could equal loss of power. also late spark could occur throwing the timing out. or finally it could cause no spark if it uses the cylinder head as the ''earth'' instead of the electrode due to the gap being too big.

DIESEL ENGINES AND FUEL SYSTEMS.....

This one i was particularly looking forward to as i knew nowt about diesels but they're suprisingly similar...

if we look at the four stroke cycle it's pretty much identical to that of the ''spark ignition'' (petrol) engine except the spark is replaced with fuelinjection....

induction:
only air pulled in... no fiel at this point.

compression:
the air is compressedd but to a much higher rate than a petrol engine... its usual that diesel engines have roughly double the compressin ratio to that of a petrol engine. at 10o before TDC (where the spark would occur in a petrol engine) the fuel is injected. due to the higher compression ratio the air is compressed and heated PAST the flashpoint of the diesel fuel. therefore when the fuel is injected it ignites.....

power:
diesel having self ignition temperature of around 400oC the diesel burns increasing the pressure in the cylinder and forcing the piston downwards.

Exhaust:
burned waste gas forced out of the cylinder as normal. it is also common for a diesel exhaust system to have a filter to reduce the carbon/soot build up.


......SHITE..... got to nip out - will continue update later today... there is lots!  :y :y :y :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 22 October 2012, 14:53:14
I doubt you will see such saprk plug issues on all but classic cars these days.

The only real issues you get now are wear (electrode recession) and sometimes fouling, all thanks to monster ignition voltages, knock control and mixture feedback control.

Diesels are simple, very simple.....more interesting once common rail comes into the equation but, sill pretty simple be it small single cylinder units or very large x00 litre jobs.

 
Title: Re: Mechanic School Blog
Post by: Nick W on 22 October 2012, 17:15:54
Or if you're feeling ghetto, checked with some plasticine..  :-[

True. :D

Or the seat of the pants if you're running hydraulic tappets. ::)

Indeed, it gets expensive if you need to buy two sets just to fill some with wax.. ;D

Why would you buy two sets when you only need to check one cylinder for clearance? Something you could quite easily do with the old followers that you won't be using.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 24 October 2012, 21:06:38
Evening chaps, as mentioned before still on half term which is why the updates aren't coming through everyday.

I've still got some stuff to update on diesles what I've learned so far but there's not much to be honest.

HOWEVER my homework is cool  8) 8) 8) 8)

I have to research the use of Turbos and Superchargers  8) 8) 8) 8)

Now from what I've learned already the turbo is connected between the exhaust manifold and exhaust pipe. The exhaust gas coming out of the manifold goes in to the turbo and turns a turbine. at its maximum heat it gets to 959oC and at its fastest UNBELIEVABLY 240,000RPM!!!! no, i didnt mistype that!!! I mean wtf!!!!!
Anyhow... this turbine is connected to an air compressor by way of a small shaft (lubricated by engine oil).
Air is pulled in by the rotating compressor, errm, then compressed and connected to the inlet manifold where the compressed air is forced in to the cylinders.
More air + more fuel = more power  8)
to get more power you would have to increase cubic capacity and normally you'd have to chuck in some more cyliners or make them bigger whatever... but this would perhaps not be practical and would also add weight. the turbo is a space and weight saving device giving increased power using the exhaust gases which exist already... kind of killing two birds with one stone  :y

This is a turbo.... labelled by moi:

(http://i1226.photobucket.com/albums/ee402/webbybear1/turbo.gif)

Also worth noting that when you compress air it increases temperature (the whole point of the afore-discussed compression ignition (diesel) engines where the air is compressed increasing the temperature to past the diesel fkashpoint...diesel injected... BOOM) so between the turbo and the cylinders (part of the intake i believe) would be an intercooler to cool the air down prior to it being sucked in to the cylinders.

SO this prompts an interesting question........ what's to stop one of us dweebs fitting a turbo? and has anyone done it? and if not possible why not? :)  

Anyway thats the basics. got a lot more to research on these but got excited so i thought id update  ;D

 :y :y :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 25 October 2012, 08:22:24
There is much more to it than just blowing air in.

As you are now producing more energy, you produce more heat and that heat has to be dealt with by the cooling system. More power also means more strain on the bottom end and drive train and hence this often needs beefing up to.

Further to this, you need to lower the static compression ratio as the dynamic one will be higher in, this means new pistons.

Very expensive to convert an engine to be blown
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 25 October 2012, 08:39:56
thanks mark :-) i didnt think about the effect on other components. What interested me was how the compressed air stays compressed between compressor and cylinders ? I know nothing in depth bout physics but would have thought that once in the inlet it would be allowed to expand again.
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 25 October 2012, 08:47:56
It would only expand if allowed to e.g. if the pipe work gets bigger.

Not all vehicles have/had intercoolers, some diesels had no intercooler, other petrol engines use charge cooling (e.g. the Lotus Caarlton) where a fine water mist is sprayed into the inlet to cool the air.

Many supercharged engines dont use intercoolers, some use charge cooling, some nothing.
Title: Re: Mechanic School Blog
Post by: Omegatoy on 25 October 2012, 09:20:01
It would only expand if allowed to e.g. if the pipe work gets bigger.

Not all vehicles have/had intercoolers, some diesels had no intercooler, other petrol engines use charge cooling (e.g. the Lotus Caarlton) where a fine water mist is sprayed into the inlet to cool the air.

Many supercharged engines dont use intercoolers, some use charge cooling, some nothing.

?????? CHARGE COOLER is a self contained unit, which cools the inlet temps by heat transfer to the water held in the charge cooler,
it does not inject water into the inlet,thats water injection!! totally different ballgame Mark :y
Title: Re: Mechanic School Blog
Post by: aaronjb on 25 October 2012, 12:20:48
Technically doesn't it all really just come under the heading of "charge cooling" whether it's air/air (commonly 'intercooler') air/water (commonly 'chargecooler') or water injection? Seeing as all three achieve the same aim - cooling the intake charge.

As an aside, you don't always need to do lots of expensive stuff to turbocharge an engine - take the little Toyota 1ZZ-FE; relatively high static compression ratio of 10.5:1, fully floating liners, peened rods but no other fancy components, even a plastic intake manifold, and it'll happily take ~10-12psi of boost to increase the crank hp from ~140 to ~300 before the bottom end lets go. In fact, the gearbox usually eats itself before the engine..

Even the 2ZZ-GE with it's even higher static compression ratio of 11.5:1 has been turbo- and supercharged without mods, though (naturally) it won't stand as much boost pressure.

Not everyone makes chocolate engines like Vauxhall ;) *ducks*
Title: Re: Mechanic School Blog
Post by: Omegatoy on 25 October 2012, 13:40:54
Technically doesn't it all really just come under the heading of "charge cooling" whether it's air/air (commonly 'intercooler') air/water (commonly 'chargecooler') or water injection? Seeing as all three achieve the same aim - cooling the intake charge.

As an aside, you don't always need to do lots of expensive stuff to turbocharge an engine - take the little Toyota 1ZZ-FE; relatively high static compression ratio of 10.5:1, fully floating liners, peened rods but no other fancy components, even a plastic intake manifold, and it'll happily take ~10-12psi of boost to increase the crank hp from ~140 to ~300 before the bottom end lets go. In fact, the gearbox usually eats itself before the engine..

Even the 2ZZ-GE with it's even higher static compression ratio of 11.5:1 has been turbo- and supercharged without mods, though (naturally) it won't stand as much boost pressure.

Not everyone makes chocolate engines like Vauxhall ;) *ducks*

lol only the v6 is made of choccy!11
water injection is there to cool the incoming charge agreed, but its used mainly to stop detonation on high turbo boost levels, :y
Title: Re: Mechanic School Blog
Post by: aaronjb on 25 October 2012, 14:53:48
lol only the v6 is made of choccy!11

That bit was only tongue in cheek, really ;)

Never did get 'round to fitting the WI to my 1ZZ-FE powered MR2 :( Then again I did have an enormous air/water chargecooler as well ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 01 November 2012, 12:35:49
Afternoon chaps, hope you're well. This isn't a school update sadly but to save starting a new thread I thought I'd post this arvo's thoughts on my own car and its diagnostics and perhaps we could discuss :)

Ok so as you may know I have had some fuel consumption troubles. I went to TB and did a TechII session where we found I have some lazy O2 sensors. So as soon as I get to swapping those out the better. I also swapped out the fuel filter for good measure. So anyway I'm happy with where we are on that front and obviously thanks to the TB-meister for his help there.

HOWEVER. he did mention that it felt low on power. I felt at the time that it was ok and didnt really pursue it. but i do feel after thinking about it that he must be right as its not spritely anymore. its quite dim-witted at the moment and sloth like. anyways i have my cambelt due next year but as vx did it i'm planning on doing that before then just in case.
there is also a ticking that doesnt go away.

just thinking out loud i'm wondering if the timing is slightly out (ticking's certainly not loud but defo there) and perhaps thats whats affecting the performance.

so i presume if its slightly out that would nacker the whole 4 stroke cycle and could contribute to the power loss and perhaps the fuel economy?

what are your thoughts? :)
Title: Re: Mechanic School Blog
Post by: Andy B on 01 November 2012, 22:15:08
.......
just thinking out loud i'm wondering if the timing is slightly out (ticking's certainly not loud but defo there) and perhaps thats whats affecting the performance.
Is the ticking not just the normal sound of an injector injecting?

so i presume if its slightly out that would nacker the whole 4 stroke cycle and could contribute to the power loss and perhaps the fuel economy?

what are your thoughts? :)
Yes! The valve over lap will be wrong .......... it could be firing with a valve still slightly open etc
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 07 November 2012, 17:20:26
Evening chaps, well just had a full week back at school after a nice half term break.

Practical was easy but theory has got very involved and I feel quite out of my depth.

Just picking up laptop from me mam's and shooting off home... so will give full update tonight  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 08 November 2012, 17:45:37
Tried to post this yesterday but my freaking internet went down  >:(

Right then chaps.... here goes....

Let's cover the first look at diesel knowledge.... what i dont understand in red  :y

Induction:
ONLY AIR is drawn in to the cylinder. The downward motion of the piston lowers cylinder pressure and creates a vacuum for the air to enter.

Compression:
The piston then moves up and compresses the air raising cylinder pressure due to the air heating up during compression. Towards the end of this stroke the diesel is injected.

Power:
After the ''Delay period'' (the time span from injection to ignition) the piston is forced down as in the normal 4 stroke cycle. It's important to note that there is flame spread when the diesel ignites. this creates shockwaves and due to the high compression ratio the shockwaves hit the piston crown and the combustion chamber. this is called ''Diesel knock'' and is the tell tale sound of a diesel  :)

There are 3 things that can be done to reduce the delay period, give quiter operation, better fuel economy and a smoother running engine:

1. increase temperature (higher compression ratio, the addition of glow plugs)
2. increased atomisation (breaking down the fuel.... increase injection pressure)
3. increased swirl (valve with a mask on the head, special piston crown shape)

next:

Direct Injection:
where the injector nozzle is directly in the combustion chamber and fuel injected straight in at the right time. simples

Indirect Injection:
where the injection of fuel is pre-swirled in to a ''pre-combustion chamber''. What i dont get is this... if the fuel and air are already mixed is it this thats pulled in on the induction stroke? or is just air pulled in and compressed and then this pre-mixed fuel/air mixture injected?

A very, very, very awful picture i've drawn (sorry its a ''paint'' jobbie) of the main components in the diesel engine...
(http://i1226.photobucket.com/albums/ee402/webbybear1/DIESEL1.png)

fuel is stored in the fuel tank and moved through the fuel lines by the lift pump. it then goes through a fuel filter (this has a water bleed and air bleed... why would water or airget in your fuel lines???  :-\
the fuel then travels to the injector pump and from the injector pump to the injectors.
NOTE the red and green lines..... red are high pressure lines from the injection pump to the injectors which is about 2000psi. the green lines are low pressure lines just to move the fuel between tank and injector pump and also the excess not used from the injectors in to the ''run off''.

Title: Re: Mechanic School Blog
Post by: Webby the Bear on 08 November 2012, 17:45:52
NEXT....

Glow plugs....

these are only found in indirect injection diesel engines and i'm informed that actually they're not that common anymore. they're specifically for cold starts where you turn the ignition on and wait for the glow plugs to warm the air sufficiently (about 10 seconds). diesels WITHOUT glow plugs (direct injection) will simply have a higher compression ratio to aid with cold starts.... air compressed more equals more heat  :y
a quick word on how glow plugs work.... there should be a wire going to them which is a live and the screw thread creates an earth. the glow plug is just a heater element basically (i liken it to the element in a bulb obviously though producing lots of heat). you can test them using a multimeter...anyone know how? not really sure what a multimeter is used for???

fuel filter:
as mentioned this has an air and water bleed screw (air at the top as its lighter and water screw at the bottom as it will sit at the bottom). the filter also has a ''primer''. is this used when all the diesel has been drained following say someone putting petrol in by mistake???

Fuel injectors:
the fuel is forced in to the injector at 2000psi through the injectors inlet port. the injector has a spring which is forced up by the pessure and allows the fuel to spray from the nozzle. when injection stops the spring closes the injector so there is no drippage. note the correct size and strength spring must be correct as too strong and it wont be allowed to open and too weak it wont close properly. the injector also has a leak off port which then, under much lower pressure, is allowed to go back to the fuel tank saving fuel :)

Rotary (or distributor) injection pump:
ok, got to be honest i dont understand this too well. can someone explain how this works? it seems that theres a cam which opens and closes two little pressy in things  ??? this allows fuel to go to all the lines and then the line for each individual injector is opened at the correct time as it is also rotating at the same speed as he cam as its driven by the same belt.... ok i'm going to stopthere as i think i'm babbling on something i really dont understand  :-[

PRACTICAL..... Stay with me as this is the easy bit  :y

Well we started our lubrication section this week. oil and filter changes to start.........piece if p*ss.  :y
nothing learned doing this that i could really tell you that would be any use apart from i got to use an oil filter wrench for the first time as the filter in my car is the paper element with thousing/24mm nut.  :y

However, a lot of the group seemed to take ages with this  ??? lazy b.......  ;D
anyway it meant me and my work partner, josh (who also is an apprentice at vauxhall and does 1 million oil/filter changes every thursday and friday lol), stormed off on our work schedule.
we moved quickly on to oil pressure switches.

Oil Pressure Switch:

Its purpose is to register whether the car has oil pressure. Good pressure and the switch will turn the light off on the dash (to signify no problems), bad pressure or lack of pressure and the switch will make a electrical connection which is linked to the bulb and the light comes on. its a very clever system......

let me type some more and providing my net holds on it will be up tonight  :y
Title: Re: Mechanic School Blog
Post by: TheBoy on 08 November 2012, 18:42:15
Only air is drawn in, diesel is injected directly (or indirectly) into the piston at the end of the compression stroke. Unlike petrol, where the fuel/air is mixed in the inlet.

Diesel - the diesel and and condensation can seperate. The filter catches this, and you can drain it off at the filter.

Not all diesels have priming pumps. The Omega TD is one that doesn't.  The nature of the system, if you run out of fuel (or open the high pressure side of the fuel system) you can get airlocks. Because air will compress, you can't get rid of them through the injectors etc, so diesels need to be bled, and in some cases primed depending on where the airlock is.

Glowplug, usually about 1 ohm resistance. Measured with meter on Ohms scale.

Diesel pump (for non common rail systems). Know how a distributor works? Its a bit like the same for diesel, rather than electric. It builds up the extrem fuel pressures, and distributes it in sequence to the cylinders. Its the pump that controls the timing (as the firing is determined when the diesel is injected in the cylinder).
Title: Re: Mechanic School Blog
Post by: TheBoy on 08 November 2012, 18:43:54
Ok so as you may know I have had some fuel consumption troubles. I went to TB and did a TechII session where we found I have some lazy O2 sensors. So as soon as I get to swapping those out the better. I also swapped out the fuel filter for good measure. So anyway I'm happy with where we are on that front and obviously thanks to the TB-meister for his help there.
As per PM, if both O2's were looking lazy (I can't remember), its possible they are both lazy, or its possible that the fault is something elsewhere that can affect the mixture on both banks...  ...eg, airleaks, maf, duff fuel etc
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 08 November 2012, 20:16:51
Sounds like your tutor does not understand diesels either.....where do I start!

As a starter, if you truely do have diesel knock (and you WOULD know) then your injecting to early.

As for glow plugs, old and new have them, there a must even on common rail, direct injection makes the engines start easier but there still needed. Older diesels had heaters either in the pre-combustion chambers or the inlet manifolds, some even had devices such as a thermostart which lit a fire in the inlet using fuel from the bleed off lines.
Title: Re: Mechanic School Blog
Post by: TheBoy on 08 November 2012, 20:19:38
Sounds like your tutor does not understand diesels either.....where do I start!
With some "guides" like before :y ;D
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 08 November 2012, 20:25:38
Right air, its bad news, you inject the fuel at very high pressure (100's of psi), liquids cant be compressed so no worries but gases can so if you get air in the system it will get to the high pressure lines and the result will be no fuel out of the injectors (as the air will compress and act like a spring). The result is that you have to be able to bleed the air out of the system after maintenance work such as changing injectors, pumps or even the fuel filter.

Diesel also sometimes has some water content, this is bad for precision items such as injector nozzles and injetion pumps (can cause corrosion and pitting) and hence it gets trapped in the fuel filter housing and needs to be drained off. This is not as big an issue as it used to be as the fuels are better (on argicultural stuff and years ago it was a bigger problem).
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 08 November 2012, 20:28:56
Your fuel pump description sounds more like an inline pump than a rotary one as an inline one has effectively a cam shaft that operates little pistons which pressurises the fuel, one for each fuel line/injector. The throttle control is via spill ports, these are little bleed off points which vent the fuel at a variable point up the injector pump piston bores. The more power required (harder you press) the higher up the bore the spill port is moved which means more fuel is delivered.

There are variations of this like PD on the VW's where the spill ports are electronic controled.

Rotary pumps are very different!
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 November 2012, 22:20:03
Right, once again sorry for the delay... been doing nothing but playing with electricity all day  ::)

However...

OIL PRESSURE SWITCHES:

I've drawn this little curcuit showing roughly how these things work:
(http://i1226.photobucket.com/albums/ee402/webbybear1/oilpressureswitch.png)
in short the oil is pressured in to the switch from the threaded end and as long as there IS pressure it will keep the circuit to the light on the dash disconnected using a spring inside. if the pressure drops (indicating a problem) then the spring will go to its relaxed state, complete the circuit and the light will come on the dash. you see it on for a couple of seconds when the car starts as pressure has yet to build up  :y

i'm still learning about electrics (as per my gen. discussion post  ::)) but even i can understand this one. very basic circuit set up.

we took a couple out (one off a tigra and one off a 206). however they are hard to find as they can be anywhere from the filter up to the top of the emgine. the 206 was right by the filter easily seen... the one on the tigra was hidden at the back of the block BEHIND some sort of manufactured lip.... vaux obviously doing it to annoy folk  ::)

anyway, thats a piece of piddle so i wont go on too long but i read the haynes and couldnt find out where it lives on the omega. anyone know and perhaps have a piccie? :)

oil pressure testing tomorrow..... stay tuned  :y

ps, with regards to the previous comments about the inline and rotary pumps..... yeah youre totally right that the inline one has a camshaft.

however what i was trying to explain was that the ''plungers'' in the rotary pump are depressed via a cam.... admittedly it doesnt look like a cam but performs the same function  :)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 12 November 2012, 11:32:49
A rotary pump has no real plungers (you could argue there is a single one but its nothing like that of the inline pump) and no real cam, thats the clever bit on them, what they effectively use is a variable quish plate to control the injection duration and a distributor to distribute the fuel.

One point to make, there is no such thing as an earth on a car, its a ground or 0V connection (sometimes referred to as chassis or chassis return), for it to be an 'earth' it would need to be connected to a 2m metal spike inserted into the 'earth' !
Title: Re: Mechanic School Blog
Post by: henryd on 12 November 2012, 11:34:06
A rotary pump has no real plungers and no real cam, thats the clever bit on them!

One point to make, there is no such thing as an earth on a car, its a ground or 0V connection (sometimes referred to as chassis or chassis return), for it to be an 'earth' it would need to be connected to a 2m metal spike inserted into the 'earth' !

Which may be inconvenient on longer runs :D :D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 12 November 2012, 12:20:14
oh ok. Thanks for that. May be worth me looking over that again. Re the earth/ground i got to be honest i dont understand electricity. Ill investigate some more :-)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 12 November 2012, 13:04:33
The simple thing to remember is that an earth is exactly what it sounds like, a strong electrical connection to 'earth'.

Have a read of the cav dpa pump service book here as the explanation of operation is quite good (with pictures!)

http://www.bluemoment.com/manuals/Lucas%20CAV%20DPA%20injection%20pump%20instruction%20book.pdf
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 12 November 2012, 18:50:59
thats great, thanks for that mate  :y
Title: Re: Mechanic School Blog
Post by: Andy B on 12 November 2012, 20:45:08
.....

One point to make, there is no such thing as an earth on a car, its a ground or 0V connection (sometimes referred to as chassis or chassis return), for it to be an 'earth' it would need to be connected to a 2m metal spike inserted into the 'earth' !

but 'earth' is a generally accepted term for the side of the battery that connects to the chassis ie positive earth or negative earth  ;) ;) ;)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 12 November 2012, 20:55:46
.....

One point to make, there is no such thing as an earth on a car, its a ground or 0V connection (sometimes referred to as chassis or chassis return), for it to be an 'earth' it would need to be connected to a 2m metal spike inserted into the 'earth' !

but 'earth' is a generally accepted term for the side of the battery that connects to the chassis ie positive earth or negative earth  ;) ;) ;)

Only in the uneducated world of the mechanic.....not in any other electrical or electronic field.
Title: Re: Mechanic School Blog
Post by: Entwood on 12 November 2012, 21:44:58
[Devils Advocate Head on]

If you allow the use of "ground" ... (americanism) why are you against the english word "earth"  :)

[Devils Advocate Head off]
Title: Re: Mechanic School Blog
Post by: Andy B on 12 November 2012, 23:23:00
.....

One point to make, there is no such thing as an earth on a car, its a ground or 0V connection (sometimes referred to as chassis or chassis return), for it to be an 'earth' it would need to be connected to a 2m metal spike inserted into the 'earth' !

but 'earth' is a generally accepted term for the side of the battery that connects to the chassis ie positive earth or negative earth  ;) ;) ;)

Only in the uneducated world of the mechanic.....not in any other electrical or electronic field.

But most 'mechanics' aren't sparks!  ;) ;) Otherwise they'd be making a living without getting their hands dirty.  ::) ::)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 13 November 2012, 08:04:48
The key point here is that this is a learning thread and in a learning thread it is important to ensure that Webby understands that the 0V is not actualy an earth and that the phrase 'earth' for vehicles is incorrect in the electrical world (and we are talking electrics).

An earth is a safety return path for fault currents.

On the 'ground' discussion, this is a different concenpt as its recognised that a ground is a return and not a safety related path for fault currents. Given the setup on a vehicle the chassis is the return path and hence may be considered a 'ground return'.

The truely correct phrase would be a 0V chassis return/connection.

 
Title: Re: Mechanic School Blog
Post by: aaronjb on 13 November 2012, 08:55:50
Shamelessly stolen from the MR2 workshop manual (electrical section):

Quote
GROUND
The point at which wiring attaches to the Body, thereby providing a return path for an electrical circuit; without a ground, current cannot flow.

(Obviously it's referring specifically to the fact that the little 'ground' picture on wiring diagrams signifies the actual physical location of a connection to the chassis)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 13 November 2012, 19:30:57
Evening guys, hope you're all well.

It's been a little while in coming but since I have fixed my phone I can now e-mail photos to myself and in turn share photos from today's practical :)

Well first of all yesterday and today was spent on lubrication system again. Yesterday was oil pressure testing; very simple.... get car up to temperature, remove oil pressure switch, screw in the pressure gauge adapter, pop on the gauge itself and take a reading at the specified revs in the Haynes. For example, the car we were on needed to read 2.8 bar @ 2000 revs. give it 2000 revs and take the reading. this will give you what oil pressure you're getting :)
it's worth noting that high pressure could indicate blocked oil galleries, clogged up filter or wrong type of oil being used. if the pressure is too low it could indicate a worn out pump.
me and my mate have took such a lead in the amount of jobs we've done that we got to actually remove an oil pump out of a clit engine, inspect it, measure it (specs in the Haynes), advise whether it should be replaced or is useable and refit on to the car.

so here's some pics of us measuring our prize....

using feeler blades and a straight edge to measure the end float...
(http://i1226.photobucket.com/albums/ee402/webbybear1/op1.jpg)

using feeler blades to measure gap between inner and outer rotor...
(http://i1226.photobucket.com/albums/ee402/webbybear1/op2.jpg)

using feeler blades to measure gap between outer rotor and the body...
(http://i1226.photobucket.com/albums/ee402/webbybear1/op3.jpg)

the specs.....(pump clearances)
(http://i1226.photobucket.com/albums/ee402/webbybear1/op6.jpg)
(http://i1226.photobucket.com/albums/ee402/webbybear1/op4.jpg)

the only ones i've seen have basically been part of the oil filter assembly. are there different versions?  :-\
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 13 November 2012, 19:33:40
...looking at the pics i cant remember if those are of a ford fiesta pump that was already off the car that we practised measuring or whether that is the clit pump we pulled out. maybe some knowledgeable person could tell?  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 13 November 2012, 19:47:32
(http://i1226.photobucket.com/albums/ee402/webbybear1/op22.jpg)
Title: Re: Mechanic School Blog
Post by: Andy B on 13 November 2012, 20:08:00
.....
so here's some pics of us measuring our prize....

using feeler blades and a straight edge to measure the end float...
(http://i1226.photobucket.com/albums/ee402/webbybear1/op1.jpg)
 ......

Turn your steel rule 90 degs so you're using the edge of it. Using it flat as you are, if your rule was bent, it'd give you an iffy reading with your feeler gauges.  ;) ;) :y :y :y
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 13 November 2012, 21:04:15
...looking at the pics i cant remember if those are of a ford fiesta pump that was already off the car that we practised measuring or whether that is the clit pump we pulled out. maybe some knowledgeable person could tell?  :y

Looks like it's off a Ford pushrod engine to me, but I'm not familiar with the clit.

There are several types. Most common these days are on the front of the block driven directly by the crankshaft as modern engines don't have a camshaft down in the block to drive it. This is the case on the GM V6. It's what you're looking at when you take the crank pulley off.
Title: Re: Mechanic School Blog
Post by: Entwood on 13 November 2012, 21:53:58
.....
so here's some pics of us measuring our prize....

using feeler blades and a straight edge to measure the end float...
(http://i1226.photobucket.com/albums/ee402/webbybear1/op1.jpg)
 ......

Turn your steel rule 90 degs so you're using the edge of it. Using it flat as you are, if your rule was bent, it'd give you an iffy reading with your feeler gauges.  ;) ;) :y :y :y

 :y :y :y

Pressing down with the "top" finger can also distort the readings .. as the rule will flex slightly .... on its side and it stays rigid ...

 ;) ;) ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 14 November 2012, 09:49:54
thanks for the tips guys ill remember that. Re which pump it is I'm fairly certain that this is the ford one. Sadly i cant get pics of the clit one as we put it back on ha ha :-)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 26 November 2012, 21:52:48
Good evening chaps, very sorry for the delay.

I think we pretty much covered the lubrication side of things.

We have moved on now to....

COOLING

Firstly i have loads of photos but again my phone isn't sending  >:( >:( >:( >:( >:( >:( >:( >:( really gotta get a new phone.

The purpose of the cooling system...

1. to ensure no overheating
2. to ensure no over cooling
3. to maintain normal and correct operating temperature.

Firstly lets look at the radiator and its function...

in short when you start your car from cold the only coolant moving around the engine is in the water jackets in the block. this is moved about by the water pump and the pressure placed on the coolant.
once up to temperature the thermostat opens allowing coolant to not only flow around the engine but most importantly moves the (recently) hot coolant from the engine to the radiator where it is cooled and then thrown back in to the engine.

it works like this:

1. conduction - heat travels from the cylinders in to the coolant by conduction (heat movement through a solid object).
2. convection - the heat then travels through the coolant en route to the radiator
3. radiation - the coolant enters the radiator hot. it then gets cooled through the radiator by the air coming in from the grill (or by the cooling fan during idle).

our first practical was to drain coolant and refill... piece of piss :)

you jack it up, brake loose the top hose (to let air in to help with draining), brake loose the bottom hose (or drainplug like in the case of the omega), all hoses back, fill her up, run the car with a few revs, wait for the bubbles to subside. DONE.

The second thing we had to do was remove the rad. ive done 3 now and have to say its a piece of piss also. generally speaking you drain the radiator of coolant, undo (normally 2 monting bolts from underneath, pop it loose from its rubber grommets. DONE

Third thing we did was to test the coolant for its percentage of antifreeze using a hydromoeter. simply press the pump and draw in some coolant from your expansion tank (if you have one) like a syringe and the amount of discs in the tube that float indicate the boiling point of your mixture. we then have a nice graph we can look at which shows what the various boiling points are compared to the exact percentage of antiofreeze mixture. 50% is what you want. not from a ''how low can you go'' chart in terms of temperatuure but also it needs 50% to help with the other things that the mixture does which is stopping rust and corrosion on the engine.

fourth thing we did was to test some thermostsats. this was well easy. take off your thermostat (generally found by trailing back the upper hose to where it meets the engine), put it in some water in a saucepan and put it on the heat. we luckily had a ''thermometer gun'' which we pressed a button towards the water and it magically took the temperature. awesome! anyway on the stats they generally have a number that is the temperature that they're supposed to open at. example, our first one said 89. so that meant it should open at 89oC. when tested ours started to open at 80oC. Bad stat and would need to be replaced as its opening early, causing over cooling and therefore wouldnt get to temperature (or would take too long).

an interesting side note on the thermostat talk is the housing. made of the most brittle material in the world. i only nipped mine up and i broke the housing :( mended it with a made gasket out of some gasket paper  :o and some proxy glue which properly stinks of actual shite!!!! horrible. and i still smell of it even after a shower  ;D

finally we came to do a pressure test to look for coolant leaks. only had a quick demo of this but we found that the stat was leaking following me breaking it  ;D obviously the gasket didnt work  ;D ;D ;D ;D

anyway, as i said im sorry for the very very late update but above is what ive done in a nut shell.

i am desperately trying to add my photos as i feel they add a lot to what im doing and trying to say at the same time.

love car bear
Title: Re: Mechanic School Blog
Post by: omega3000 on 27 November 2012, 07:53:05
Quote
we found that the stat was leaking following me breaking it   

 ;D ;D
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 27 November 2012, 08:08:22
1. conduction - heat travels from the cylinders in to the coolant by conduction (heat movement through a solid object).
2. conduction - the heat then travels via the coolant en route to the radiator
3. radiation - the coolant enters the radiator hot. it then gets cooled through the radiator by the air coming in from the grill (or by the cooling fan during idle).

Corrected that for you, you wont see a convection cooling system these days.

The coolant is used as a transport medium for the heat, it effectively stores it temporarily whilst its moved to the radiator.

Also note that hydrometer testing of coolant only tells you half the story as it indicates only the freeze point. One of THE most important things that antifreeze has is an anti corrosion additive that protects the cylinder head, head gasket etc from corrosion.

Bottom line is if its 2 years old (basic stuff) or 4 years old (advanced stuff) then it MUST be changed no matter what the hydrometer reading says
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 November 2012, 10:13:07
thanks mark. Very clear as usual :-) re the convection, would the coolant being a transfer medium effectively be convection? The problem i have is that although these are basic terms for most sadly i havent done any science in years and am having to do extra research when we get a new term quoted at us. By th way i Havent really gone in to too much detail on the pressure in the system. I'll try and add that tonight as this is very important :-)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 27 November 2012, 10:45:54
In answer to the convection, no not really is the answer, have a little look at this:

http://www.wisc-online.com/Objects/ViewObject.aspx?ID=sce304

If the system had no water pump then yes, convection would be the means by which the system operated as the heat differentials setup convection currents (some vintage cars were like this and had no water pump!). Reality is that the liquid is force pumped and hence no chance for the convection currents to be be setup hence its actualy conduction cooled.

Pressurised systems are important to understand, hopefuly you have a grasp on the fact that the boiling point of a liquid is dependent on pressure and hence a pressurised coolant system results in the boiling point of water rising above the 100 degC level.

Similarly if you lower the pressure water will boil at room temperature (this is one of the reasons why you vac down air con systems as it boils off any moisture)
Title: Re: Mechanic School Blog
Post by: 2woody on 27 November 2012, 11:47:45
the proper term is "pump-assisted thermo-siphon".

most cooling systems work at least partly convectionally - i.e. the coolant enters the bottom of the engine and flows upwards and enters the radiator at the top, cooling as it falls. This generally makes bugger all difference when running, but can be quite important to prevent "afterboil", when the coolant circulates on its own without the engine running.

some engines, however, are "reverse-flow", where the coolant enters the heads first.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 November 2012, 16:48:34
thanks for the replies chaps and mark ill check that link when I'm at a computer. What I'm about to say is going to open a can of worms ha ha. But. My tutor said that the water pump Isnt what forces water round the system and that its the pressure created when it heats up. He said the term water 'pump' is actually inaccurate as it doesn't create any pressure.
Title: Re: Mechanic School Blog
Post by: Entwood on 27 November 2012, 17:03:30
thanks for the replies chaps and mark ill check that link when I'm at a computer. What I'm about to say is going to open a can of worms ha ha. But. My tutor said that the water pump Isnt what forces water round the system and that its the pressure created when it heats up. He said the term water 'pump' is actually inaccurate as it doesn't create any pressure.

No pump in the world creates pressure  :)  All pumps create FLOW. Pressure is only resistance to flow.

Maximum pressure is at minimum flow, maximum flow is at minimum pressure ... :)

Most pumps are rated as xy/galls(litres)/minute ... ie FLOW,
A very few pumps will be rated at a combination of flow/pressure ... xy galls(litres/min @ z psi(g/sq.cm)

An engine waterpump  is NOT rated for pressure but being a pure vane type will produce more flow at higher rpm, and the system is designed NOT to resist that flow by dynamic pressure.

The increase in static pressure by the radiator cap is a totally different aspect.. :)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 28 November 2012, 08:17:29
thanks for the replies chaps and mark ill check that link when I'm at a computer. What I'm about to say is going to open a can of worms ha ha. But. My tutor said that the water pump Isnt what forces water round the system and that its the pressure created when it heats up. He said the term water 'pump' is actually inaccurate as it doesn't create any pressure.

Lol, hes very wrong.

They do say those that can do and those that cant teach  ;D ;D

If his statement was totaly true then the water would elave the kettle when it was boiled. As per 2Woody, there is a thermo syphon effect based on heat differentails but, its far from enough to cool the engine and hence the pump. Perhaps you should remove the water pump on his car to prove your point  :y ;D

And as per Entwoods statement, the pump is not there to create pressure (there will be a measureable pressure differential across the pump) its there to 'move' the coolant effectively.

The real pressure increase in the system is due to the heating of the coolant.
Title: Re: Mechanic School Blog
Post by: 2woody on 28 November 2012, 19:54:27
Have just fixed a Discovery, which was running as a thermo-siphon only - the coolant pump driveshaft had broken.

The thermo-siphon was good enough to cool the engine at idle and up to about 10mph with very little load, so powerful enough for some running I guess.
Title: Re: Mechanic School Blog
Post by: martin42 on 28 November 2012, 20:57:13
water pump is just the same as central heating pump it pushes water around,doesnt create pressure,pressure comes because its basically a sealed system.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 December 2012, 12:08:56
Afternoon fellas, sadly no real update for a while. I've had exam mocks and practical assessments on what i've learned so far so sadly no new awesome info from webby the car bear :(

i do have some pics to upload though from our assessments so ill upload those tonight.

i do have an interesting topic though and thats oil changes.

i know this is going to open flood gates but hell, whats the point in me blogging if i dont spark debate lol

we had a test on lubricantion system (already covered in this blog) and i mentioned to my tutor that i change my oil every 3k miles. he couldnt believe it and said that was flat out too often. i said the haynes says 5000 but ''from what ive read'' the recommended is 3000.

we then looked on autodata and it said every 10000 miles.


SO. What do you guys reckon? Anybody agree with the 10k? or we all happy that its 3k.
if i was to comment i know for a fact that my engine seems happier doing it every 3k. there seems to be a noticeable smoothness after a change. however, the cost is obviously a lot.

so what do we think?

:)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 December 2012, 12:29:39
oh and one more quickie about oil....

when you're down to '0' miles on the range and bang on empty, did i read somewhere that there are actually still 3 gallons in the tank?

obviously important to know from an mpg working out point of view :)
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 06 December 2012, 12:31:59
Autodata simply shows the manufacturer's recommendation, which the trade will go by, of course, otherwise customers will complain that they are carrying out unnecessary work.

This recommendation is a compromise between a long-lived engine and a cheap car to run that will be attractive to fleet managers and customers who know no better. After all, the manufacturer doesn't care what happens to the car after the warranty has expired, and the cynic in me would say that they believe that the sooner it's worn out the sooner you'll be queuing up to buy a new one. ;)

The fact is that you can't change oil "flat out too often". ;)

Another thing to consider is that even the manufacturer specifies a shorter interval for "extreme conditions". I would say anything other than a rep blasting up and down a motorway 5 days a week does constitute "extreme conditions". Urban driving and cold starts do it no favours.

How often you decide to change it depends on your usage pattern, attitude to the costs and time involved and personal preference, but nothing but a top-of-the-line synthetic oil will be in good condition after 10,000 miles of typical driving, IMHO, so you're doing the right thing in my book.

Consider also that later petrol Omegas specified an interval of 20,000 miles. :o (Conditional on the use of a higher spec of oil, admittedly)
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 06 December 2012, 12:34:24
oh and one more quickie about oil....

when you're down to '0' miles on the range and bang on empty, did i read somewhere that there are actually still 3 gallons in the tank?

obviously important to know from an mpg working out point of view :)

Don't rely on the range. It's not always accurate and it's based on average consumption rather than the level left in the tank!

You don't need to know how much is left to work out fuel consumption accurately. Just fill to the brim and divide the miles you have covered by the fuel you have put back in.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 December 2012, 12:37:39
Thanks for clarifying kevin. as i said i honestly believe it makes a difference. its definitely smoother without a doubt and i will keep changing mine that often so thanks for that. just wondered what the consensus was ;)

thanks for clarifying the capacity thing too ;)

as a matter of pure interest though...forgetting the range.... if it does get to the bottom of empty (last red notch) then do you roughly have 3 gals left?
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 06 December 2012, 12:42:04
I've no idea. I've never run out of petrol. ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 December 2012, 12:42:39
I've no idea. I've never run out of petrol. ;)

 ;D

no worries. cheers mate  :y
Title: Re: Mechanic School Blog
Post by: albitz on 06 December 2012, 13:04:59
There is nothing like three gallons left when the MID is reading 0. One gallon would be more likely imo. :y
Possibly 3 when the fuel ight comes on,although I would have thought it to be more like 2. :-\
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 December 2012, 13:10:40
There is nothing like three gallons left when the MID is reading 0. One gallon would be more likely imo. :y
Possibly 3 when the fuel ight comes on,although I would have thought it to be more like 2. :-\

cheers albus....thought that sounded a bit off  :y :y
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 06 December 2012, 14:41:46
Be warned that there will be times when it'll run out before the mid reads 0, though. It's not an exact figure, as I said. ;)
Title: Re: Mechanic School Blog
Post by: TheBoy on 06 December 2012, 18:41:38
Don't take too much notice of MID, its easy to confuse.

I've had it hit zero, yet do 18m up the motorway (admittedly at 56mph, fully clenched), and only take 73l.  I've also had it run out with Range=8m.

Once the fuel light starts flashing, think about getting more.
Title: Re: Mechanic School Blog
Post by: dbdb on 06 December 2012, 20:51:53
I've tested the MID 'range' function a few times, twice on my 98 Reflection and once on my 2001 Elite.  Easy to do, take a full petrol can and funnel then drive along a road with a hard shoulder, ideally a dual carriage way not a motorway (where it may be illegal).

With the Reflection it ran out on the dot of zero both times.  With the elite it did almost one mile after zero was displayed.  It is so accurate I do wonder if the pump is told to cut out on zero whether there's any fuel left or not.

Yes it calculates an running average  so if you go down a long hill at range 5 miles and then come up a hill don't be surprised if it drops to 0 in much less than 5 miles.  What  mine won't do though is run out when it still says 5.  As regards slope I suspect it doesn't affect the tank take off, is it designed to take the last drop whatever angle it is at within reason?

According to the manual "The range is calculated from the current contents of the fuel tank and the average
consumption over the last 12 to 20 miles" This may account for people running out unexpectedly or getting more miles thanwhen it says 0.  Best to reset it using the stalk button when it gets low. 

Well worth doing once as it gives you the confidence to use almost the whole tank and the evidence to tell SHMBO not to keep panicking.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 December 2012, 21:03:35
Right then lads. As promised. photos :)

Testing a stat from a nissan micra. real easy to do. fill a saucepan with cold water. put in the stat. put it on the heat. when it starts to open up it should be at the temp. indicated on the stat capsule. this one was shagged. it was meant to open at 89oC. It opened at 80!  :y
(http://i1226.photobucket.com/albums/ee402/webbybear1/bbbb.jpg)
This is me making a gasket for the stat housing. i forgot to ask if this was special gasket paper. either way it didnt work as i suspected  ::)
(http://i1226.photobucket.com/albums/ee402/webbybear1/bbbbbbb.jpg)
this is my work partner proudly showing off our prize from our cooling assessment (even though i'm the one who drained the system, removed it from the car, cut up my fingers on a sharp edge of the cooling fan and got covered with around 6 litres of coolant  >:( ::) :y)
(http://i1226.photobucket.com/albums/ee402/webbybear1/bbbbb.jpg)
this is me about to test my mates nackered coil pack using a volt meter set on the ohmes range (remember i posted about the mondeo). weirdly the coilpack was up to spec  ???
(http://i1226.photobucket.com/albums/ee402/webbybear1/bbbbbbbb.jpg)
and the spec from autodata.
(http://i1226.photobucket.com/albums/ee402/webbybear1/bbbbbbbbbbb.jpg)

i had to be shown how to test this coilpack as we havent done ignition systems yet so dont ask me any questions about it as i dont know!  ;D

Title: Re: Mechanic School Blog
Post by: dbdb on 06 December 2012, 21:17:32
I've had it hit zero, yet do 18m up the motorway (admittedly at 56mph, fully clenched), and only take 73l. 

Up to two additional litres can be gradually added after the automatic shut-off.
Title: Re: Mechanic School Blog
Post by: Lazydocker on 06 December 2012, 21:23:58
Yes it calculates an running average  so if you go down a long hill at range 5 miles and then come up a hill don't be surprised if it drops to 0 in much less than 5 miles.  What  mine won't do though is run out when it still says 5.  As regards slope I suspect it doesn't affect the tank take off, is it designed to take the last drop whatever angle it is at within reason?

I've never yet encountered any car that uses every last drop, even when empty and cut out ;) Some leave as much as a couple of litres :o
Title: Re: Mechanic School Blog
Post by: dbdb on 07 December 2012, 00:39:48
I wonder then if the slope does matter, if you are on the flat with a very low tank and than change to a slope will it cut out? All my tests were pretty much on the flat. But even on a hill a bit of braking is going to throw the back of the tank contents forward over the pump, even with baffles.

Makes me think even more that the fuel is electronically cut off when it decides the tank is too low rather than keep pumping every last drop.  On each of the three tests I did when it cut out it went immediately, no spluttering.  I didn't try ignition off and restarting; I wonder if that might reset something.
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 07 December 2012, 00:43:27
I suspect once the fuel pump has sucked the swirl pot in the tank dry, there isn't enough fuel for it to re-prime. I don't think there's anything clever to vut it off. Engine stops when it sucks air.
Title: Re: Mechanic School Blog
Post by: omega3000 on 07 December 2012, 07:58:59
I know years ago we used a cutout from a cornflake box to make up gaskets .. worked a treat with a bit of sealant .
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 07 December 2012, 08:30:13
Resistance is not a great method for checking coils, a test plug with variable gap (upto 40-50mm for modern ignition systems) is the only method that gives a true test of the setup.

The reason being that an important part of the coil is the iron core, it is this that stores the energy in the form of magnetic flux and hence when the core corrodes, the capacity to store magnetic flux drops and the spark energy drops......and in this common failure mode, the resistance values are unchanged.  :y
Title: Re: Mechanic School Blog
Post by: Andy B on 07 December 2012, 11:08:19
.....The reason being that an important part of the coil is the iron core, it is this that stores the energy in the form of magnetic flux and hence when the core corrodes, the capacity to store magnetic flux drops and the spark energy drops......and in this common failure mode, the resistance values are unchanged.  :y

How do you remember all this stuff?  ???   ;D  ;D
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 07 December 2012, 11:22:04
.....The reason being that an important part of the coil is the iron core, it is this that stores the energy in the form of magnetic flux and hence when the core corrodes, the capacity to store magnetic flux drops and the spark energy drops......and in this common failure mode, the resistance values are unchanged.  :y

How do you remember all this stuff?  ???   ;D  ;D

Its basic electrical engineering (first year theory)  :y
Title: Re: Mechanic School Blog
Post by: 05omegav6 on 07 December 2012, 11:55:46
I wonder then if the slope does matter, if you are on the flat with a very low tank and than change to a slope will it cut out? All my tests were pretty much on the flat. But even on a hill a bit of braking is going to throw the back of the tank contents forward over the pump, even with baffles.

Makes me think even more that the fuel is electronically cut off when it decides the tank is too low rather than keep pumping every last drop.  On each of the three tests I did when it cut out it went immediately, no spluttering.  I didn't try ignition off and restarting; I wonder if that might reset something.

The estate can cut out parked on a bit of camber if your heading towards the red :o Takes a lot more fuel than you might think to get it running again, as Albs will testify ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 07 December 2012, 12:27:41
cheers guys  :y as said i cant comment as i aint learned ignition yet  but thanks for the explanation :y

as i dont have any updates due to assessments there is something i would like to talk about thats been bothering me in my short learning curve.

that is....

RUSTY BOLTS.

As you probably know i was the proud owner of ralf and after scrapping the old boy im really pissed off i didnt get the cats off and take more stuff off to be honest. however in fairness to myself i own onlythe halfords tool kit (mainly with awfully pointless double hex ring spanners) and a bottle of wd40.

i made a half hearted attempt to get the bolts undone. no chance. especially as i couldnt get the car on stands (i dont trust my stands anymore and am replacing) and it was on a slope  ::)

Anyway....

i want a little step-by-step cut out and keep guide as to how to tackle any bolt.... i think it should be as follows... do you agree....

spanner/socket
penetrating oil then spanner/socket
heat
last resort...angle grinder and replace bolts

but what about in tight areas like exhaust manifolds?  :-\

as per the addition of heat is there anything that you can buy for the ''DIYer''? i have a very good heat gun but im thinking that wont get anywhere near the temp needed.

SO i suppose the topic should be ''what can the diy'er use for heat''? :)

discuss.


Title: Re: Mechanic School Blog
Post by: aaronjb on 07 December 2012, 13:23:33
Skip the WD40 and use a proper disassembly oil like PlusGas..

For home use your best option is Oxy/Propane - slightly less potentially lethal than Oxy/Acetylene and doesn't require a license to store the bottles. Expensive for infrequent use, though.. really good straight propane torch might do it, but I've never tried.

With limited access a very good HSS/Cobalt bit and a steady hand with a drill is your only real option.. it's annoying, takes forever and some practice!
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 07 December 2012, 13:31:01
Thanks Aaron ;)

if i did want to have a home kit is there one that anyone could recommend?
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 07 December 2012, 13:31:20
by kit i mean blow torch kit to remove rusty bolts  :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 07 December 2012, 14:41:42
Look for a Bernzomatic torch and then get either a disposable Propane bottle (hot) or a MAPP gas bottle (hottest).

They can be used for plumbing, heating, brazing etc
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 07 December 2012, 14:48:42
Look for a Bernzomatic torch and then get either a disposable Propane bottle (hot) or a MAPP gas bottle (hottest).

They can be used for plumbing, heating, brazing etc

cheers mark  :y :y :y

are these a good edition to the home worker would you suggest? at least i'd never not be able to remove a bolt again  ;D
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 07 December 2012, 16:05:13
Its the next best thing to a Portapack! (which are pricey!).

Plus very useful for general things such as plumbing, fire lighting etc
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 07 December 2012, 16:06:11
cheers mate.

would my heat gun set on high be any good?
Title: Re: Mechanic School Blog
Post by: aaronjb on 07 December 2012, 16:28:37
would my heat gun set on high be any good?

Electric one as used for stripping paint etc? Not even remotely ;) I have a butane torch and even that doesn't get things hot enough..
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 07 December 2012, 16:54:21
cheers mate.

would my heat gun set on high be any good?

Unlikely, you need a GOOD blow torch with a controlable flame and at least propane (much hooter than Butane).
Title: Re: Mechanic School Blog
Post by: Andy B on 07 December 2012, 17:01:58
..... (first year theory)  :y

That was a long long time ago for some!  ::) ::)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 07 December 2012, 17:40:23
this the sort of thing mark? :)

http://www.ebay.co.uk/itm/Bernzomatic-Blow-Torch-/281032823873?pt=UK_DIY_Materials_Plumbing_MJ&hash=item416edc9441
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 07 December 2012, 18:11:03
or this.....

http://www.amazon.co.uk/Bernzomatic-Solid-Brass-Adjustable-JT682/dp/B0055S2JCO

what do i need in addition to this? just a gas bottle? sorry i know nowt about this
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 07 December 2012, 20:43:32
I have a TS7000, you need to check on their website to make sure it can work on mapp and propane. You can get the gas from the likes of B&Q at the larger stores
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 08 December 2012, 12:24:22
thanks mark. i was watching ETCG and i noticed this in the corner...
(http://i1226.photobucket.com/albums/ee402/webbybear1/benzermatic.png)
so presumably (as long as i have the right canister) this would just be hooked up to my ''nozzle thingy'' and would be wireless
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 10 December 2012, 08:32:02
Exactly, the nozzle simply screws onto the top of one of those cylinders.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 12 December 2012, 22:38:42
Good evening guys.

Well a great week of learning. All assessments ended last week. Got some excellent results. Very happy.

SO This week we've started ignition.

We first of all looked at the early distributor and the ''contact breaker'' system...

(http://i1226.photobucket.com/albums/ee402/webbybear1/distributordiagram.png)

In short the battery will provide 12V up to the coil when the ignition switch is on. It will flow through the primary winding (less tightly wound coil) and up to the condensor back to an earth (the chassis). this is charging the primary coil and producing an electro-magnetic force.
on the condensor there is a cam that when turned it will hit the breaker points and break the circuit. the magnetic field around the primary coil will collapse and the current will then be looking for a path back to earth.... the only place it can go....through the secondary (tightly wound) coil. being much more tightly wound will give even more force and produce out of it around 20kV which will be sent through the HT leads up to the spark plug.
What i don't get is this.... will the current when the circuit is broken ''back up'' and go the the secondary winding or will it ''jump'' from primary to secondary?

you must understand i'm learning about all this for the first time and am currently looking in to the discovery of electromagnetism but its hard work  :-[ i love the fact that the course (for me) is getting difficult to understand as obviously i want to be challenged but i want to obviously understand it in the end  :y

the funny thing i found about the above was this.... obviously on todays cars there is simply a coilpack and HT Leads. i doubt (apart from the one we had specially in the shop on a stand) i will ever work on one of these so i can competently remove a coilpack, test it with a multimeter set to look at resistance and compare to the manu. spec. so really i suppose i'm aslready able to do what they can do in the garages.....

this however was to try and understand it. if that makes sense.

testing coil packs is easy (i'm sure Mark mentioned multi-meter not being totally accurate) but for the most part it was:

Set multimeter to ohms (its mark is the little horseshoe looking thing on the dial range)....
(http://i1226.photobucket.com/albums/ee402/webbybear1/multimeter.jpg)

secondary check..... probe sister cylinders (1 and 4, 2 and 3) take reading
primary check..... probe electrical connector points 1&2 and 2&3. take reading

quite straightforward.

leads should be measured and should be less than 10kohms for every 300mm in length (normally come out around 5kohms i believe).

it gets serious next week though as we have to do ignition timing with a strobe light  :o ??? ??? ??? ??? and we get in to advanced/retarded timing. we touched on it a bit (i.e. timing needs to alter accodring to engine speed) but then he started to talk degrees of crankshaft BTDC and i got well confused.... i get the principle but how on Earth can you measure it when the cars running  ??? ??? ???

Anyway, ive got a little bit more to update so expect another one this week  8)
Title: Re: Mechanic School Blog
Post by: Andy B on 12 December 2012, 22:44:20
The thing you need to learn is, that if ever you buy/own a car with 'points' is to ditch them ASAP & fit an electronic ignition system. Points were crap! You set them to 0.0??", used the car for an afternoon & they were were out again ...... one side of the points had a spike & t'other side had a pit. The best place for a set of points was ............... the bin!  ;) ;) ;)
Title: Re: Mechanic School Blog
Post by: Andy B on 12 December 2012, 22:50:57
.... but then he started to talk degrees of crankshaft BTDC and i got well confused.... i get the principle but how on Earth can you measure it when the cars running  ??? ??? ???

.........

When you have your timing gun/strobe looking at the fixed mark on the timing cover & the mark at top dead centre, you turn the dizzy one way or the other till the marks line up (you mark each with a little white paint so you can see them) Some timing guns have the ability to dial the degrees before top dead centre that's required for the particular car, others just do top dead centre & it's up to you to mark your crank pulley at the appropriate mark (it'll have TDC and various others ie 2 4 6 degrees BTDC)

EDIT Mark will do the theory of primary & secondary windings etc  :y :y
Title: Re: Mechanic School Blog
Post by: omega3000 on 12 December 2012, 23:17:11
The thing you need to learn is, that if ever you buy/own a car with 'points' is to ditch them ASAP & fit an electronic ignition system. Points were crap! You set them to 0.0??", used the car for an afternoon & they were were out again ...... one side of the points had a spike & t'other side had a pit. The best place for a set of points was ............... the bin! ;) ;) ;)

Nightmare on the kickstart lawnmower  :'(
Title: Re: Mechanic School Blog
Post by: Andy B on 12 December 2012, 23:26:43
....

Nightmare on the kickstart lawnmower  :'(

I can't remember what's on my pull start Atco lawn mower   :-\
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 13 December 2012, 09:01:40
As mentioned before, testing a coil pack with a multimeter actualy tells you nothing more than the coils are ok, it fails to identify the common coil pack failure mechanism and gives zero guarantee that the coil or coil pack is ok......in short, its a poor test!

Lets start with the basic operation.

As you already state, the positive side of the coil primary is connected to 12V when the ignition is on (note, on some cars its via a resistor which is shorted out during cranking so as to maintain high coil volts when starting.....so not always this simple!). The negative side connects to the points or electronic ignition system (note the condenser is a transient suppressor to minimse arcing across the points contacts so treat it as a secondary item rather than a primary par of the operation).

When the engine is cranked either of the following happens;

1) A cam rotates in the distributor which opens the points

2) An electronic pickup is triggered to give a timing signal, an electronic switch then 'opens' in the same way as the points.

The basic operation of the coil is this.

When the points or electronic switch are closed current passes through a coil of wire which is wrapped around an iron core (you can see the core on some coils and on the V6 dis pack). As this happens, a magnetic field is 'induced' (created) in the iron core which effectively acts as an energy store.

When the points or electronic switch open, the current flow stops and the magnetic field in the iron core starts to collapse. The energy from this has to go somewhere but there is no longer a circuit on the primary (the points/electronic switch are 'open circuit') and so a current is induced in the secondary winding (this is wound onto the same iron core).

The secondary winding has many more turns than the primary which results in a much higher voltage (due to the turns and a little bit of theroy called V=L x (dI/dt) which is a little complicated for most unless they have excellent maths  :y ) being produced.

This gives a spark of many 10's of KV.

All very simple and the modern systems work on the same principle all be it with more coils and no distributor to distribute the spark to the plugs (distributor is repalced by electronic switches).

A few pointers:

1) The time that the points/electronic switch remain closed is reffered to as the 'dwell angle', this is actualy the time available to induce the magnetic field in the coil and in the case of mechanical systems (e.g. points) is related to the points gap at maximum opening and hence setting the gap is important (you can get dwell meters which measure the dwell). Electronic systems do this 'automaticaly' by monitoring the curret through the coil. If Dwell is to low, the spark energy will be less (less magnetic field 'stored' in the coil)

2) Testing coil output requires a special test plug with adjustable gap, when removed from a compression cycle, a spark plug will only need a few thousand volts to spark.....this is NOT a good test method......and the screwdriver to the head is also not a great science either!. As a guide, a spark will generaly jump around 1mm for every 1mm of gap!

3) Its a weekly moan of mine regarding 'Earths' as earths do not appear on cars and it is an incorrect term. A key reason why I harp on about it is because 'Earths' are very important and critical to safe operation of many electrical items and hence need care and respect. A vehicles body is a 0V point or a chassis return, to make it an earth you would need to connect it via a large metal cable to a large metal spike driven into the ground  :y. In summary, when working on a real earth (e.g. house wiring etc) you need to treat it with great repsect and care as the fault current it may have to handle can be 100's of amps plus even on a low current system where as a chassis retrun could be as simple as a screw through the body work which is man enough to carry the operating current of the device.

On the lawnmowers, they are probably a magneto ignition switch with a capacitor system.
Title: Re: Mechanic School Blog
Post by: Entwood on 13 December 2012, 09:31:41

<big snip>

The secondary winding has many more turns than the primary which results in a much higher voltage (due to the turns and a little bit of theroy called V=L x (dI/dt) which is a little complicated for most unless they have excellent maths  :y ) being produced.

<big snip>


Calculus  :) :) :)  REAL mathematics .. :)   

Differentiating Current with respect to Time ... .. love it ..:y :y :y :y :y :y :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 13 December 2012, 09:40:56
It explains nicely how faster (e.g. electronic) switching can generate more V's  :y
Title: Re: Mechanic School Blog
Post by: Andy B on 13 December 2012, 11:10:10
.....

Calculus  :) :) :)  REAL mathematics .. :)   

Differentiating Current with respect to Time ... .. love it ..:y :y :y :y :y :y :y

I can't find that button on my calculator!  ???  ???  ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 13 December 2012, 18:10:44
As mentioned before, testing a coil pack with a multimeter actualy tells you nothing more than the coils are ok, it fails to identify the common coil pack failure mechanism and gives zero guarantee that the coil or coil pack is ok......in short, its a poor test!

Lets start with the basic operation.

As you already state, the positive side of the coil primary is connected to 12V when the ignition is on (note, on some cars its via a resistor which is shorted out during cranking so as to maintain high coil volts when starting.....so not always this simple!). The negative side connects to the points or electronic ignition system (note the condenser is a transient suppressor to minimse arcing across the points contacts so treat it as a secondary item rather than a primary par of the operation).

When the engine is cranked either of the following happens;

1) A cam rotates in the distributor which opens the points

2) An electronic pickup is triggered to give a timing signal, an electronic switch then 'opens' in the same way as the points.

The basic operation of the coil is this.

When the points or electronic switch are closed current passes through a coil of wire which is wrapped around an iron core (you can see the core on some coils and on the V6 dis pack). As this happens, a magnetic field is 'induced' (created) in the iron core which effectively acts as an energy store.

When the points or electronic switch open, the current flow stops and the magnetic field in the iron core starts to collapse. The energy from this has to go somewhere but there is no longer a circuit on the primary (the points/electronic switch are 'open circuit') and so a current is induced in the secondary winding (this is wound onto the same iron core).

The secondary winding has many more turns than the primary which results in a much higher voltage (due to the turns and a little bit of theroy called V=L x (dI/dt) which is a little complicated for most unless they have excellent maths  :y ) being produced.

This gives a spark of many 10's of KV.

All very simple and the modern systems work on the same principle all be it with more coils and no distributor to distribute the spark to the plugs (distributor is repalced by electronic switches).

A few pointers:

1) The time that the points/electronic switch remain closed is reffered to as the 'dwell angle', this is actualy the time available to induce the magnetic field in the coil and in the case of mechanical systems (e.g. points) is related to the points gap at maximum opening and hence setting the gap is important (you can get dwell meters which measure the dwell). Electronic systems do this 'automaticaly' by monitoring the curret through the coil. If Dwell is to low, the spark energy will be less (less magnetic field 'stored' in the coil)

2) Testing coil output requires a special test plug with adjustable gap, when removed from a compression cycle, a spark plug will only need a few thousand volts to spark.....this is NOT a good test method......and the screwdriver to the head is also not a great science either!. As a guide, a spark will generaly jump around 1mm for every 1mm of gap!

3) Its a weekly moan of mine regarding 'Earths' as earths do not appear on cars and it is an incorrect term. A key reason why I harp on about it is because 'Earths' are very important and critical to safe operation of many electrical items and hence need care and respect. A vehicles body is a 0V point or a chassis return, to make it an earth you would need to connect it via a large metal cable to a large metal spike driven into the ground  :y. In summary, when working on a real earth (e.g. house wiring etc) you need to treat it with great repsect and care as the fault current it may have to handle can be 100's of amps plus even on a low current system where as a chassis retrun could be as simple as a screw through the body work which is man enough to carry the operating current of the device.

On the lawnmowers, they are probably a magneto ignition switch with a capacitor system.

WOW. Thats a lot of detail. thanks mate  :y :y :y

when testing coil output is that the thing that attaches to the end of a HT lead and you can see the spark outside the cylinder?

so dwell angle... that is really the period of time that the gap is open for.... therefore more of the charge can flow through the secondary winding? i presume its dwell ''angle'' as the nose of the cam opening the breaker points will determine the length of opening time??

 :y :y :y :y
Title: Re: Mechanic School Blog
Post by: Andy B on 13 December 2012, 20:15:50
.

 
Title: Re: Mechanic School Blog
Post by: Entwood on 13 December 2012, 20:28:21
.

Talkative tonight .......   :)  :)
Title: Re: Mechanic School Blog
Post by: Andy B on 13 December 2012, 21:59:51
.

Talkative tonight .......   :)  :)

No  ::)


No longer a delete option  ;) ;)
Title: Re: Mechanic School Blog
Post by: Shackeng on 13 December 2012, 22:23:58
Just as well, I like a bit of quiet. 8)
Title: Re: Mechanic School Blog
Post by: Andy B on 13 December 2012, 22:34:39
Just as well, I like a bit of quiet. 8)

 :-X :-X  ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 December 2012, 23:09:25
Evening fellas,

Had an awesome session today. A lot of stuff really clicked and it was nice cos its been a sort of ''catch up'' week where we've gone over any practical stuff we wanted to re-cover.

So this week I've done a DOHC timing belt (a big 1.8 mitsubooooshi if i'm right in thinking). difficult without the right tools... namely a cam locking tool  >:( but i got there with a bit of grit, determination and a bit of ingenuity ;)
did a crank sensor removal, test and replace. did this on a tigra and like the omega only god knows what i'd do if i actually had to remove the wire from the engine bay for a new one (we just disconnected it for testing purposes). its like wedged between the block and the crap coming off the bulkhead and below. that would be a nightmare!!!

most fun of all and something i was actually amazed by (little things) was testing ignition timing.....
this is a pic of the set up on the car.....strobe light gun connected to a second battery, the clamp hooked on to no.1 HT lead and just about to start the car ready to go.....
(http://i1226.photobucket.com/albums/ee402/webbybear1/strobe1_zps5c1c8ba0.jpg)
this is a photo of the strobe gun in action on the crank pulley... sorry its a bit dodgy but it was real hard getting a good photo...
(http://i1226.photobucket.com/albums/ee402/webbybear1/strobe2_zps8bc7025a.jpg)

now i shall explain how it works.

in that second photo you should be able to see by the pulley a little bit of plastic whith numbers 15, 10,  & 0

you check the spec on Autodata and this avensis' ignition timing was (or should be) 10o at idle... so basically the spark occurs 10o before TDC compression.
You set the gun's dial at 10o, turn the car on and point the gun at the crank pulley.
the timing notch/mark should then show 0. if it doesnt your ignition timing is off and should be investigated.

i'm taking the miggy in to school tomorrow for a good winter health check so i really wanna get the gun on it  :y :y :y :y :y :y

anyway, sadly i have no other updates but we have theory tomorrow so ill update what i learn then.

choi for now  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 December 2012, 23:11:26
i should have mentioned that the gun fires a strobe light every time the spark occurs... and it knows this as its hooked up to no.1 HT lead.
soz thought i should mention that  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 December 2012, 23:12:51
and sorry again  ::)

but actually that 2nd pic is actually really good... you can actually see the crank mark at '0' when i flashed the light. didnt notice that before
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 18 December 2012, 23:25:35
Struggling to think of a car from the past 10-15 years that you cna set the timing on, or one these days that you can connect a timing light to!

Testing a crank sensor, did you have an oscilloscope then or was it a (another not so useful) resistance test?
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 December 2012, 23:27:35
Struggling to think of a car from the past 10-15 years that you cna set the timing on, or one these days that you can connect a timing light to!

Testing a crank sensor, did you have an oscilloscope then or was it a (another not so useful) resistance test?

yeah sorry mark, should've mentioned that if you find the timing to be out there isnt anything you can do  unless it was an oild school distributor other than replace a component... coilpack? ;D

and yeah it was resistance checks  :-[
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 18 December 2012, 23:36:03
Struggling to think of a car from the past 10-15 years that you cna set the timing on, or one these days that you can connect a timing light to!

Testing a crank sensor, did you have an oscilloscope then or was it a (another not so useful) resistance test?

yeah sorry mark, should've mentioned that if you find the timing to be out there isnt anything you can do  unless it was an oild school distributor other than replace a component... coilpack? ;D

and yeah it was resistance checks  :-[

Sadly, as per the resistance tests on the coil, they dont tell you to much on the crank sensor (not the most common failure mode).

As for change a component.....coil pack will make no difference, pretty much nothing that will (Ecu controls timing based on knock and crank position plus calculated enegine load)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 December 2012, 23:40:18
Struggling to think of a car from the past 10-15 years that you cna set the timing on, or one these days that you can connect a timing light to!

Testing a crank sensor, did you have an oscilloscope then or was it a (another not so useful) resistance test?

yeah sorry mark, should've mentioned that if you find the timing to be out there isnt anything you can do  unless it was an oild school distributor other than replace a component... coilpack? ;D

and yeah it was resistance checks  :-[

Sadly, as per the resistance tests on the coil, they dont tell you to much on the crank sensor (not the most common failure mode).

As for change a component.....coil pack will make no difference, pretty much nothing that will (Ecu controls timing based on knock and crank position plus calculated enegine load)

thats interesting cos when i asked ''and why would you need to perform this test'' the answer was a bit vague lol

so i take it that in the real world if the timing was off (or you even got that far to check) it'd be a case of checking out any fault codes and if none then a replacement ECU? and furthermore i'm thinking off the top of my head that that shouldnt really happen anyway (or if it does it will be once in a blue moon)?

Thats ashame re the resistance tests. what sort of test should really be carried out?
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 18 December 2012, 23:48:29
Fault code analysis is a good start, live data might tell you something (less likely) but viewing the signal on a scope is the ultimate  :y

As for replacement ecu....if its running at all then its very unlikely to be the ecu
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 December 2012, 23:54:24
Fault code analysis is a good start, live data might tell you something (less likely) but viewing the signal on a scope is the ultimate  :y

As for replacement ecu....if its running at all then its very unlikely to be the ecu

looking in to scopes is our christmas homework  :y :y :y :y

but im wondering if theyve actually got one that we can look at data on  :-\
Title: Re: Mechanic School Blog
Post by: symes on 19 December 2012, 19:49:16
Keep one in the boot along with dwell meter along with carb=that way drive to drags change carb do timing undo headers and viola instant v8 roar  :y no use whatsoever on any car from late 90's though.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 19 December 2012, 21:01:18
Keep one in the boot along with dwell meter along with carb=that way drive to drags change carb do timing undo headers and viola instant v8 roar  :y no use whatsoever on any car from late 90's though.

 ;D ;D ;D ;D
i think he was trying to teach us that so we get a better understanding of everything. although its a bit point;ess as nowt is adjustable. if it dont work replace it  ::)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 January 2013, 19:56:44
Right chaps..... HEEEEEEEEEEEEEELP  ;D ;D ;D ;D ;D

Bear unblievably forgot to do his christmas homework  :-[

Below is a picture of a scope trace of a contact breaker ignition system (primary charging and then magnetic field collapsing, high voltage through secondary winding to the spark plug)

(http://i1226.photobucket.com/albums/ee402/webbybear1/scopetrace_zps9db77374.jpg)

point 1 shows the points cloed and the primary winding being charged.

i need to highlight on the scope where the points have opened and the spark occurs.... is that the spike at ms point 0.0?

if the spark duration ends ar 1.0 ms i'm going to say the spark occurs for 1.0 milisecond? am i right? :)

the rest i can answer myself. i think  ;D

cheers guys
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 06 January 2013, 20:36:48
Keep one in the boot along with dwell meter along with carb =that way drive to drags change carb do timing undo headers and viola instant v8 roar  :y no use whatsoever on any car from late 90's though.

 ;D ;D ;D ;D
i think he was trying to teach us that so we get a better understanding of everything. although its a bit point;ess as nowt is adjustable. if it dont work replace it  ::)

I disagree. A scope is a great diagnostic tool on any car old or new, you've just got to know what to look for. It can show you cam and crank sensor outputs, ignition primary waveforms, fuel injector, ICV and EGR valve drive signals. You might not have any adjustments, but knowing what you expect to see and comparing this with what you actually see is a great diagnostic tool. You can still look at the ignition signal and determine what the fault is likely to be.

Anyway, to your homework. Once the points have opened you are looking at the primary voltage from the coil, and this will follow the secondary voltage reasonably closely, although will be lower due to the turns ratio of the coil. So, you get a huge peak as the points open. Here the current in the coil has stopped suddenly due to the points opening and back to Marks V=L(di/dt), di/dt is large, so voltage is large. We have 200 volts at the primary of the coil. We will have much more at the secondary (probably 40,000 volts or more).

This high voltage quickly ionises the air in the gaps in the distributor cap and spark plug and a spark forms. The spark draws current from the coil, reducing the rate of decay of the magnetic field, and this reduces the voltage seen at the primary, in this case to around 40 volts. Eventually, the current in the spark reduces to a point where the spark can no longer be sustained. The rest of the energy in the coil just dissipates in the internal losses in the coil. This is what the wavy line after 1ms shows. Notice that the voltage doesn't return to 0V after this. That's because the points are now open and we're looking at the voltage across the points, not the coil, so we see the 12 volts from the battery until the points close again.

So, yes, I'd say the spark duration is about 1ms in this case. :y

The big spike to 200V is where the points open.

The point where this collapses down to 40V is where the spark starts.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 January 2013, 20:54:03
thanks for the info kev. that confirms exactly what i thought  :y :y :y

the comment (well from me anyway) wasnt about the use of a scope. it was about spending so much time learning the old distributor system and contact breakers, seperate coils etc.

on reflection however i think its good to know how these work as the modern coilpacks/ CPP's are easier to unerstand  :y

this bit of homework (that ive just completed in 20 mins  :)) was our first look at the scope.

i've seen videos of their use and love the idea. i do hope we do a lot more as they're awesome. for diagnostics ;)

sadly however we start fuel systems tomorrow.... i say sadly cos i bet me balls its gonna be fuel filter R&Rs all day  ::)
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 06 January 2013, 21:03:36
the comment (well from me anyway) wasnt about the use of a scope. it was about spending so much time learning the old distributor system and contact breakers, seperate coils etc.

Well, the principles are exactly the same on more modern cars, there just aren't any adjustments to make, so it's well worth learning the theory on a mechanical ignition setup so you can apply it when you get problems with a more modern system. :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 January 2013, 21:09:07
the comment (well from me anyway) wasnt about the use of a scope. it was about spending so much time learning the old distributor system and contact breakers, seperate coils etc.

Well, the principles are exactly the same on more modern cars, there just aren't any adjustments to make, so it's well worth learning the theory on a mechanical ignition setup so you can apply it when you get problems with a more modern system. :y

that was my way of thinking when i made the comment.... whats the point in learning about the workings of a part that in modern vehicles (which ill likely only ever work on) can't be fixed, adjusted, serviced or worked on.

but as you say having reflected its good to know how these things work  :y :y :y
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 06 January 2013, 22:45:01
the comment (well from me anyway) wasnt about the use of a scope. it was about spending so much time learning the old distributor system and contact breakers, seperate coils etc.

Well, the principles are exactly the same on more modern cars, there just aren't any adjustments to make, so it's well worth learning the theory on a mechanical ignition setup so you can apply it when you get problems with a more modern system. :y

that was my way of thinking when i made the comment.... whats the point in learning about the workings of a part that in modern vehicles (which ill likely only ever work on) can't be fixed, adjusted, serviced or worked on.

but as you say having reflected its good to know how these things work  :y :y :y

Because if you know how it works, you can diagnose problems with it, and the basic principles are the same with modern cars. :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 07 January 2013, 21:13:12
Right then girls... TERM 2.... THANK GOD!!!  :) :) :) Can't tell you how much I've missed it  :)

A bit of housekeeping with the blog first. I really think I should have headed up each section when we moved on to a different area e.g. cooling, ignition, engine etc. SO that's what I'm going to do from now on. :)

New term, new topic:

FUEL SYSTEMS:

Ok so first thing is to explain the workings of a carburettor, specifically we learned to start withe the ''fixed jet'' carburettor. Even though they're obviously not in modern cars it's important to understand as there's a lot of theory around the vacuum side of things.
A handy cut-out-and-keep guide courtesy of google :)
(http://i1226.photobucket.com/albums/ee402/webbybear1/carb6_zps8438d4dc.jpg)
some notes anout this...
the progression hole is only a small hole and is used at idle as not much fuel is needed.i believe it relies solely on the vacuum created between the cylinders and the (at this point) closed throttle plate.
when the throttle plate is opened (by pressing the accelerator) the vacuum is placed on the fuel from the ''main jet'' and pulled in with the in-rushing air.
The choke plate is closed on start up so the pressure's higher hence drawing more fuel in for the initial fast idle, then opens as less fiel is needed when at temperature.
(note, these comments are based on what i can remember from this mornings lesson so if anythings incorrect do say  :y)

our Carburettor in bits...
 (http://i1226.photobucket.com/albums/ee402/webbybear1/carb1_zps8dbfb80e.jpg)
(http://i1226.photobucket.com/albums/ee402/webbybear1/carb2_zps6300868a.jpg)

Sorry for the quality of that first photo.

in the first pic you can make out 3 ''areas''. the one on the right is the float chamber. this is simply where the fuelstays while it awaits its journey to the cylinders. its stopped from overflowing by the float which, when full, goes to the top of the chamber and the inlet is stopped by a plunger.
the two areas with a bit of gold in them are the chambers down to the throttle plates (two on this carb).
machined between the float chamber and the throttle plate chambers are the main jets (you cant see them though sadly).
in the second photo the black plastic at the top is the float and the main part of this component is the choke plate.

As I predicted the next thing on our list was fuel filters  ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) ::) i hate these things and the stupid ''quick release'' clips that aren't quick release at all. theyre ridiculous. i'm glad my omegas modified with fuel line and jubilee clips and thats how its staying!!!  8) 8) 8) 8)

Anyway, the fuel filter on the pug 206 we had to do...
(http://i1226.photobucket.com/albums/ee402/webbybear1/carb3_zps2e36279f.jpg)
this is our second one on an N reg Fiesta. a total shite box of a car but christ the filter was easy. in the engine bay and the clips you pressed lightly and it sweetly came apart  8)
(http://i1226.photobucket.com/albums/ee402/webbybear1/carb5_zps6589c69b.jpg)
one thing to do when removing a filter is to depressurise the system. now on the two cars that we did there were schrieder (spell chack) valves. however if there wasnt a schreider valve you can hook up the fuel regulator to a tool with a gauge (cant remember the name... midi or mini something  :-\) and this gauge with fuel line will draw the pressure out.
I personally dont think any depressurising is necessary. i've never done it on my car and the fact is you still lose a load of fuel when they come apart. also access (as we know from the V6) can be bloody limited. time vs lost fuel. cover it in a rag. job done. what do you think?

finally, we were informed by the lads that worked on the fiesta before us that when it was running it was surging. no ICV on this car but had a word with the tutor and basically we ripped the air filter out to be presented with a pipe the lads hadnt put back properly  ::) but anyway this was what was underneath.... what looks like a carb and i guess does exactly the same function but the tutor called this a ''single electrode fuel mixer''..... a carb then  ::)
(http://i1226.photobucket.com/albums/ee402/webbybear1/carb4_zps40b5ef0b.jpg)

Anyway we tidied up the other lads' mess, hose clamped lose pipes and the car is running super sweet now  :y :y :y :y

more updates tomorrow  :y :y :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 07 January 2013, 21:24:16
Its a single point injection throttle body, an electronic carb so a throttle valve with a single fuel injector to replace the carb jet. Often referred to as TBI (throttle body injection) spi (single point injection) etc.

OK systems but pretty obsolete these days and not great on larger Cc engines as its difficult to deliver small quantities of fuel for idle with such a large injector ( which has to be sized to meet Max required fueling)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 07 January 2013, 21:28:49
Its a single point injection throttle body, an electronic carb so a throttle valve with a single fuel injector to replace the carb jet. Often referred to as TBI (throttle body injection) spi (single point injection) etc.

OK systems but pretty obsolete these days and not great on larger Cc engines as its difficult to deliver small quantities of fuel for idle with such a large injector ( which has to be sized to meet Max required fueling)

that was it Mark. sorry, been a long day. i got him to explain it but this was dead in the centre of the manifold so what i couldnt work out was how an injector with a single point could distribute fuel evenly.... or would there be like a pre-injection chamber where thats sorted out?  :)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 07 January 2013, 21:32:41
Works the same way a carb does, produces a fine atomised mist of fuel which gets drawn into the cylinders  :y :y
Title: Re: Mechanic School Blog
Post by: Andy B on 07 January 2013, 21:35:56
Works the same way a carb does, produces a fine atomised mist of fuel which gets drawn into the cylinders  :y :y

Mark ..... you have a pm  :y  :y

(Nothing to do with this thread though  ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 07 January 2013, 21:38:38
Works the same way a carb does, produces a fine atomised mist of fuel which gets drawn into the cylinders  :y :y

nice one mate  :y :y

I've just remembered something I would like to talk about and although not totally about my schooling it is relevant. And that's getting a career.

This level qualification will be completed in May. i then have the option of doing the next level next year (for just one more year).

i'm kinda missing having money so what i'd like to know is what's the industry like for getting a job these days if anyone knows? i know of 3 of the lads who have scored part time jobs in local garages. i always fancied going in to a dealership thouhg... although obviously i have no work experience. are dealerships better? or local garages?

anyone with any info wud be great  :y
Title: Re: Mechanic School Blog
Post by: tidla on 07 January 2013, 21:59:52
Keep one in the boot along with dwell meter along with carb =that way drive to drags change carb do timing undo headers and viola instant v8 roar  :y no use whatsoever on any car from late 90's though.

 ;D ;D ;D ;D
i think he was trying to teach us that so we get a better understanding of everything. although its a bit point;ess as nowt is adjustable. if it dont work replace it  ::)

I disagree. A scope is a great diagnostic tool on any car old or new, you've just got to know what to look for. It can show you cam and crank sensor outputs, ignition primary waveforms, fuel injector, ICV and EGR valve drive signals. You might not have any adjustments, but knowing what you expect to see and comparing this with what you actually see is a great diagnostic tool. You can still look at the ignition signal and determine what the fault is likely to be.

Anyway, to your homework. Once the points have opened you are looking at the primary voltage from the coil, and this will follow the secondary voltage reasonably closely, although will be lower due to the turns ratio of the coil. So, you get a huge peak as the points open. Here the current in the coil has stopped suddenly due to the points opening and back to Marks V=L(di/dt), di/dt is large, so voltage is large. We have 200 volts at the primary of the coil. We will have much more at the secondary (probably 40,000 volts or more).

This high voltage quickly ionises the air in the gaps in the distributor cap and spark plug and a spark forms. The spark draws current from the coil, reducing the rate of decay of the magnetic field, and this reduces the voltage seen at the primary, in this case to around 40 volts. Eventually, the current in the spark reduces to a point where the spark can no longer be sustained. The rest of the energy in the coil just dissipates in the internal losses in the coil. This is what the wavy line after 1ms shows. Notice that the voltage doesn't return to 0V after this. That's because the points are now open and we're looking at the voltage across the points, not the coil, so we see the 12 volts from the battery until the points close again.

So, yes, I'd say the spark duration is about 1ms in this case. :y

The big spike to 200V is where the points open.

The point where this collapses down to 40V is where the spark starts.

This is a great site for practice videos and sample waveforms.

http://www.picoauto.com/automotive-library.html

The Frank Massey stuff is great too.

Using a scope i have solved a few jobs that code reading even in the hands of specialists have not been able to solve.
Title: Re: Mechanic School Blog
Post by: Lazydocker on 07 January 2013, 23:37:33
Webby, I'd be looking at independent garages myself... Get some all round experience and, if you're lucky, they might put you through as a MOT tester ;)
Title: Re: Mechanic School Blog
Post by: omega3000 on 08 January 2013, 06:03:58
That filter on the fiesta looks massive  :o Took a lot of carbs to bits in the past but mainly motorcycle ones and repaired a few housings with chemical metal that lasted years  :-X
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 08 January 2013, 19:19:57
Ok boys, I'm home, relaxed, I have my tool kit, a lamp light and I have a multi-meter borrowed from the lovely technician from school  8)

I'm praying someone can answer my Q's tonight as I only have this multi-meter for tonight (don't want to push my luck too much  :))

These were the results from a TechII session with TB (thanks mate):

When he turned up, O2 BLMs:
Integrators, around 100 (low)
Idle (B1 - 190, B2 - 160) (high)
Partial Load, around 130 (good)

Air/fuel ratio (Rich/Lean) seemed sluggish at idle, flipped at about 1Hz at 2000rpm, lazy lamdas, both banks.

Reset BLMs, took for drive, all around the 130 mark, except at idle, when integrators crept to 150ish, with Air/Fuel showing lean until then, then flipped at 0.33 - 1Hz

Seemed slightly down on power to me, although Webby said otherwise. MID readings for instantaneous consumption seemed quite low - I'd expect mid to high 30s average when cruising 50-60mph, reality was mid/high 20s. MID has correct 035 config, and readings seem to match Webby's experience of it using more fuel recently. This leads me to suspect that the engine is really using that amount of fuel, rather than leaks (which I couldn't detect, or smell).

After test run, brakes still cold. EGR can get to about 55% before the thing really splutters. Injector cut-off exactly as expected.

MAF, at idle, with A/C off, 9kg/hr.


Last Sunday I got the EGR cleaned out (thanks Martin) and I did an oil change and she runs lovely and seems to want to go!  ;) but still getting the high consupmtion.

People who know me know I have to have my house in order otherwise I get all confused hence the massive thread (so apologies fo that) but this is what I'm going to do. All you have to do is tell me if I'm wrong or right in my approach... oh and questions in red   8)

INTAKE AIR TEMP. (IAT) SENSOR

I've actually done this already tonight 8) As per Autodata it says to switch ignition off, disconnect the sensor, check ambient temp. and check resistance between the sensor terminals (two of them).
Autodata says ambient temp. should be 15-30oC. And the resistance readings as per below. I had just ran the car for about twenty minutes so things were ''toasty'' under there so I presume that's why I'm getting a high resistance reading of 2040 ohmes (2.04 on the 20k scale).  
(http://i1226.photobucket.com/albums/ee402/webbybear1/IATMM_zps37bf477d.jpg)

MAS AIRFLOW (MAF) SENSOR

I haven't done this one yet as it's just started raining  >:( (am going out there again irrespective of the rain as I'm determined to clear this up). Anyway the procedure I'm going to follow is this...I have two options for voltage... AC or DC. Which one should I use to check the voltage???
(http://i1226.photobucket.com/albums/ee402/webbybear1/MAFMM_zpse21e8740.jpg)

THROTTLE POSITION SENSOR (TPS)

Again, I haven't done this one because of the rain but again procedure I'll follow...When it says access TP sensor multi-plug terminals... but don't disconnect the multi-plug... wellhow the hell am I supposed to check it??? lol. And both of these checks on the image (Fig. 4 & Fig. 5) I'm supposed to check the actualsensor itself and not it's plug going in???
(http://i1226.photobucket.com/albums/ee402/webbybear1/TPSMM_zpsfca14d8a.jpg)

COOLANT TEMP. SENSOR (CTS)

Obviously, this isn't one for tonight but I want to get this bad boy done at the weekend. But here's the procedure I'm going to follow:
(http://i1226.photobucket.com/albums/ee402/webbybear1/CTSMM_zps4690553a.jpg)

CHECKING BATTERY VOLTAGE

I don't think this is going to affect fuel consumption (or could it????  ??? but I am aware it can affect performance and as I have the meter I may as well check it... should be 12.5, not drop below 10 on start up and go to around 14.5 when running, right???

EXHAUST LEAKS

As per Cem's posts (thanks for them mate) I am going to get the car up on the ramps at school and get someone to give it the beans while I'm underneath looking for smoke or any sign of exhaust leaks between the exhaust manifold and the O2 sensors.

If all of the above work out fine then I'm thinking I need to look at the commpression and do a leak down test. If that's ok then I'd have to reasonably conclude it's the injectors that are bad (leaking perhaps?)

Lot of info there but if someone could confirm all of the above I'll love you forever  :-* :-* :-* :-* (not that I don't anyway you big set of girls  :y :y :y
Title: Re: Mechanic School Blog
Post by: Shackeng on 15 January 2013, 10:48:09
Still enjoying your blog Webby, and I hope you get some answers to your last. HNY :y :y :y
Title: Re: Mechanic School Blog
Post by: tidla on 15 January 2013, 18:08:12
If you do take your car into college,dont leave it in bits unattended.

Fellow student brought his pride and joy in to replace the spark plugs.

Some clever dick decided to "add" a washer while the plugs were out.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 29 January 2013, 22:20:02
Sorry no update on this for a while chaps but obviously crimbo has been and on our return we haven't been working on cars :(

we've been making ''stud extraction blocks''.

Basically this is our ''metal work assessment'' whereby we have to join, drill, tap threads, file and measure two metals.

we were given one rectangle of alluminium and one rectangle of mild steel. we had to fit them together with two M10's at either end and fit 3 M8s in the middle, saw the setbolt heads off the M8s and then they are tools that are used to practise stud extraction on..... so making a tool thats designed just for oractise on. odd! lol


anyway we finished making them today and will be practising removing the broken studs on monday. quite handy stuff to know. and learning to tap threads was really cool. the taps themselves (tools that cut threads in holes) are really expensive. tecchie said £130 for a set of 3 M10 taps  :o :o :o :o made worse when one of the kids broke one by fekking about  >:( as said before i like the kids but sometimes theyre just dickheads!!!!

ill try and get a pic of my finished work. quite proud as aint made anything since school  :-[ 8)

in theory we been learning about air intake and exhaust systems,

air intake real easy. same with exhausts really except remembering the gases produced and what could be wrong if any of them are high are quite difficult.

ill do a full update after tmorrows theory hopefully.  :y






Title: Re: Mechanic School Blog
Post by: Andy B on 29 January 2013, 22:32:33
... saw the setbolt heads  ...
set screws  ;) ;) ;)



... the taps themselves (tools that cut threads in holes) are really expensive. tecchie said £130 for a set of 3 M10 taps  :o :o :o :o  ....
There are taps & taps but a decent make aren't that much.  ;) ;) ;) (although I was quoted £30-odd for a single 1/2 BSP tap! :o) Just take your time, use a decent tap wrench (not a 6" adjustable spanner  ::)) 1/2 a turn forwards & a turn-ish back to break the swarf. It's a bugger to try & get a broken tap out ........ apparently!  ::)
http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2045573.m570.l2736&_nkw=m10+taps
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 29 January 2013, 22:41:01
... saw the setbolt heads  ...
set screws  ;) ;) ;)



... the taps themselves (tools that cut threads in holes) are really expensive. tecchie said £130 for a set of 3 M10 taps  :o :o :o :o  ....
There are taps & taps but a decent make aren't that much.  ;) ;) ;) (although I was quoted £30-odd for a single 1/2 BSP tap! :o) Just take your time, use a decent tap wrench (not a 6" adjustable spanner  ::)) 1/2 a turn forwards & a turn-ish back to break the swarf. It's a bugger to try & get a broken tap out ........ apparently!  ::)
http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2045573.m570.l2736&_nkw=m10+taps

ah yeah, set screws sorry  ::) :y :y

well the kid that was messin around basically sheered it in half leaving the one half in the tap wrench and the other half in the stud block... not to mention the bits that came flying past my face at 2000mph  >:( >:( >:( >:( really wasnt happy. if you break something thats fine.. but to do it while dicking about is not on... same fekking kid who set the fire alarm off  ::) ::) ::)

anyway, theres one lad there (real nice kid, got a lot of time for him) who does work with his dad on cars and trucks. with no fuss he  picked up a really thin punch and started knocking it round on the tiny bit that was sticking out. seemed to come very natural to him, was very impressed. i think he'll do well.  :y :y :y
Title: Re: Mechanic School Blog
Post by: Andy B on 29 January 2013, 22:48:58
... with no fuss he  picked up a really thin punch and started knocking it round on the tiny bit that was sticking out. seemed to come very natural to him, was very impressed. i think he'll do well.  :y :y :y

There is such an animal as a tap extractor ...... http://www.ebay.co.uk/itm/WALTON-10103-TAP-EXTRACTOR-3-FLUTE-3-16-/350680858355?pt=LH_DefaultDomain_3&hash=item51a6353ef3 (not a good picture  :()
They have a leg that slides down into the flute of the snapped off tap. I have to admit that I've never had a great deal of success with them though, if a tap has broken, it must've been bloody tight and the legs on these extractors tend to ben before the remnants of the tap come out.

This might be a bit better
(http://t2.gstatic.com/images?q=tbn:ANd9GcQlGUltdALoaEFYC5Igj4S1gbwiHCFF8sRUYiiQNG6BGb9MWCZi)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 29 January 2013, 22:55:54
that looks interesting. ill look to see if theyve got a set at school... they seem to have most things

just trying to think when/where the drilling/tapping may come in handy from an automotive perspective in the future.. any ideas? my initia thought would be if the sump bolts stuck and mangled? or perhaps creating a drain plug for the autobox?  :-X ;D :y
Title: Re: Mechanic School Blog
Post by: Andy B on 29 January 2013, 23:04:44
that looks interesting. ill look to see if theyve got a set at school... they seem to have most things
Might have .... you can only ask  :y



just trying to think when/where the drilling/tapping may come in handy from an automotive perspective in the future.. any ideas? my initia thought would be if the sump bolts stuck and mangled? or perhaps creating a drain plug for the autobox?  :-X ;D :y
Most tapping on a car is just clearing out an old thread or if you have sheared of a bolt (eg exhaust to down pipe on a V6)  want to drill out & re-tap. Same procedure for using Helicoils or Threadcerts.  ;)
Title: Re: Mechanic School Blog
Post by: Shackeng on 30 January 2013, 22:40:31
that looks interesting. ill look to see if theyve got a set at school... they seem to have most things

just trying to think when/where the drilling/tapping may come in handy from an automotive perspective in the future.. any ideas? my initia thought would be if the sump bolts stuck and mangled? or perhaps creating a drain plug for the autobox?  :-X ;D :y

For example, I drilled out a damaged thread in my TD sump (which had been overtightened by a VX mechanic  >:( >:( >:(), tapped it, and fitted an oversize sump plug. :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 04 February 2013, 19:51:53
More bench work this week. Has been actually very, very enjoyable except getting a loada swarf stuck in my hand  :'(

First thing on the menu was stud extracting.

So you've sheared a set screw or bolt and you cant get it out with mole grips or something as tits flush with what its screwed in to... what do you do.... i'll tell you  :D

1.) get a centre punch and make a punch in the centre of the stud.
2.) small diameter metal drill bit in your drill. drill hole about 1/2 - 1 cm deep.
3.) turn in you stud extractor
stud comes out

it does it because the extractor is left hand threaded so turning it anti clockwise means it will grip and as it tightens it turns the broken stud out

the name for it was an ''easy out'' if anyone considers buying one :)

next we did screw thread repairs. ive already detailed that earlier in the thread (no pun) so i wont go through that again.

if you got a screw thats sheared  but you still got some sticking out, obviously you can get mole grips or pliers on it, but if its too tight theres speacial sockets we used that you attach a ratchet, turn clockwise and it locks on to the bit sticking out. then undoes  8)

just a bit of diy info.... i got my first ever tool chest at the weekend. it was given to me and after a bit of degreasing and wd40'ing it looks great. man does it serve a purpose. i consider my tools in two sets. my main tools is the halfords carry case set. i love it and when i get to pro i think ill still use this as its so handy. but then there are things that the tool chest is perfect for like breaker bars, spare wrenches, chisels, punches, pliers etc etc. ill tr yand get a pic. well proud of it  8)
Title: Re: Mechanic School Blog
Post by: TheBoy on 04 February 2013, 19:59:09
I broke a die yesterday (die creates a thread on a bolt, tap creates thread in a nut), cleaning up a damaged thread on a TRE.

Trouble with stud extractors like Easy-Outs, which you won't come across in a classrom environment, is sometimes they can be rusted in solid.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 04 February 2013, 20:02:09
I broke a die yesterday (die creates a thread on a bolt, tap creates thread in a nut), cleaning up a damaged thread on a TRE.

Trouble with stud extractors like Easy-Outs, which you won't come across in a classrom environment, is sometimes they can be rusted in solid.

thats very true, TB. As mentioned before in a previous post we actually made the stud extraction block to practise on. and the fact we only torqued them to 20nm i can well believe it would be a lot harder in the real world.

how did you break a die?  :o

 :y
Title: Re: Mechanic School Blog
Post by: symes on 04 February 2013, 20:02:59
I broke a die yesterday (die creates a thread on a bolt, tap creates thread in a nut), cleaning up a damaged thread on a TRE.

Trouble with stud extractors like Easy-Outs, which you won't come across in a classrom environment, is sometimes they can be rusted in solid.
try doing snapped stud on a 1931 ford side valve engine >:( ******** nitemare of a job took 2 days :D
Title: Re: Mechanic School Blog
Post by: Andy B on 04 February 2013, 20:04:15
I broke a die yesterday (die creates a thread on a bolt, tap creates thread in a nut), cleaning up a damaged thread on a TRE.

 ......

As above .... HTF do you manage to break a die?   ??? ??? (split die or die nut?  ;))
Title: Re: Mechanic School Blog
Post by: Andy B on 04 February 2013, 20:04:54
I broke a die yesterday (die creates a thread on a bolt, tap creates thread in a nut), cleaning up a damaged thread on a TRE.

Trouble with stud extractors like Easy-Outs, which you won't come across in a classrom environment, is sometimes they can be rusted in solid.
try doing snapped stud on a 1931 ford side valve engine >:( ******** nitemare of a job took 2 days :D

I'd give up & get it spark eroded  ;) ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 04 February 2013, 20:16:39
ps, think i'm going to snap this up... £1.40 with free delivery  :o

http://www.ebay.co.uk/itm/5-PIECE-PCE-DAMGED-SCREW-EXTRACTOR-CASE-BOLT-SCREW-STUD-REMOVER-EASY-OUT-/120970567505?pt=UK_Hand_Tools_Equipment&hash=item1c2a685f51
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 04 February 2013, 20:26:16
A piece of advice, don't ever buy easi outs as that way you will never be tempted to use them.

If you do get tempted to use them then the normal outcome is a stud or bolt still stuck fast in a piece of metal that now has an undrillable lump of hardened steel in it.
Title: Re: Mechanic School Blog
Post by: Abiton on 04 February 2013, 20:27:45
I bet they're really high quality...
Title: Re: Mechanic School Blog
Post by: henryd on 04 February 2013, 20:30:06
I broke a die yesterday (die creates a thread on a bolt, tap creates thread in a nut), cleaning up a damaged thread on a TRE.

Trouble with stud extractors like Easy-Outs, which you won't come across in a classrom environment, is sometimes they can be rusted in solid.
try doing snapped stud on a 1931 ford side valve engine >:( ******** nitemare of a job took 2 days :D

I'd give up & get it spark eroded  ;) ;)

That's what we used to do back many moons ago in our toolroom,we had spark and wire eroders,spark eroders very slow going though but about the only thing that will touch a broken tap or stellite drill.
Title: Re: Mechanic School Blog
Post by: Andy B on 04 February 2013, 20:34:52
A piece of advice, don't ever buy easi outs as that way you will never be tempted to use them.

If you do get tempted to use them then the normal outcome is a stud or bolt still stuck fast in a piece of metal that now has an undrillable lump of hardened steel in it.

I witnessed a genuine miracle on Saturday afternoon! An Easy-out was used with success on a sheared/rotted off stainless 'stud' in a stainless filler bowl!!! I really thought it had snapped when it suddenly removed the stud with all Almighty CRACK!!!!!!!!!!!  ??? And .......... the tap wrench used was a 6" adjustable!  ;D ;D ;D

 ;D ;D ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 04 February 2013, 20:36:27
Miracle, praise the lord.

Hateful things
Title: Re: Mechanic School Blog
Post by: symes on 04 February 2013, 20:40:07
Miracle, praise the lord.

Hateful things
+1 :y
Title: Re: Mechanic School Blog
Post by: Andy B on 04 February 2013, 20:40:59
Miracle, praise the lord.

Hateful things

I have on the odd occasion used them with some success, but on the whole, you're right. End result is a hardened Easy-out snapped off in the end of the bolt/stud you wanted removed in the first place. Generally, if the bolt head snapped off, it was f....ing tight & your Easy-out will be piddling in the wind.  :y


Title: Re: Mechanic School Blog
Post by: henryd on 04 February 2013, 20:43:36
Miracle, praise the lord.

Hateful things

I have on the odd occasion used them with some success, but on the whole, you're right. End result is a hardened Easy-out snapped off in the end of the bolt/stud you wanted removed in the first place. Generally, if the bolt head snapped off, it was f....ing tight & you're Easy-out will be piddling in the wind.  :y

Yep,bloody useless things created to make a difficult job harder. :-X
Title: Re: Mechanic School Blog
Post by: symes on 04 February 2013, 20:51:50
Miracle, praise the lord.

Hateful things

I have on the odd occasion used them with some success, but on the whole, you're right. End result is a hardened Easy-out snapped off in the end of the bolt/stud you wanted removed in the first place. Generally, if the bolt head snapped off, it was f....ing tight & you're Easy-out will be piddling in the wind.  :y

Yep,bloody useless things created to make a difficult job harder. :-X
did he/she have anything to do with omegas ;D ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 04 February 2013, 20:53:19
I scrapped a KA cylinder head after somebody snapped the horrible taper seat spark plug off that had welded itself of into the head and they then paniced and tried an easily out which also snapped.

One of the other issues is that if the item you are trying to remove is tight then the easiout taper can actually spread the remaining metal making it tighter
Title: Re: Mechanic School Blog
Post by: Lazydocker on 04 February 2013, 20:58:56
Used an easy out once, never again ::)

Actually, as it happens, I didn't snap it because I was sensible and paid attention to the warning signs but vowed from that day on I wouldn't ever try one again
Title: Re: Mechanic School Blog
Post by: biggriffin on 04 February 2013, 21:01:31
used one of them horrid things once,got such a telling off, o the innocent of youuf.
Title: Re: Mechanic School Blog
Post by: Andy B on 04 February 2013, 21:02:25
... then the easiout taper can actually spread the remaining metal making it tighter

Which is why you drill the smallest hole you can get away with ...... obviously the smallest Easy-out isn't going to remove a 1" BSW bolt  ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 04 February 2013, 21:08:01
ok, so its clear i shouldnt have updated tonight, not a lot of love for the easy-outs  ;D ;D ;D ;D

why do they snap? speed of use or just shit quality?
Title: Re: Mechanic School Blog
Post by: henryd on 04 February 2013, 21:08:50
... then the easiout taper can actually spread the remaining metal making it tighter

Which is why you drill the smallest hole you can get away with ...... obviously the smallest Easy-out isn't going to remove a 1" BSW bolt  ;)

No but folk have tried it,honest,then wonder why it didn't work :P
Title: Re: Mechanic School Blog
Post by: henryd on 04 February 2013, 21:11:38
ok, so its clear i shouldnt have updated tonight, not a lot of love for the easy-outs  ;D ;D ;D ;D

why do they snap? speed of use or just shit quality?

There are plenty of shite quality but you have to know what you are doing even with the decent ones and even then it can go tits up.
Title: Re: Mechanic School Blog
Post by: Lazydocker on 04 February 2013, 21:17:16
As above. I've actually had better results with the type designed for screws (like a reverse countersink) and you can be more forceful as it isn't going to snap in the stud :y
Title: Re: Mechanic School Blog
Post by: TheBoy on 04 February 2013, 21:28:26
ok, so its clear i shouldnt have updated tonight, not a lot of love for the easy-outs  ;D ;D ;D ;D

why do they snap? speed of use or just shit quality?
If a M8 bolt shears because its too tight/rusted in, an easi-out made from 4mm hardened steel isn't going to do much, except fail.
Title: Re: Mechanic School Blog
Post by: TheBoy on 04 February 2013, 21:29:35
I broke a die yesterday (die creates a thread on a bolt, tap creates thread in a nut), cleaning up a damaged thread on a TRE.

 ......

As above .... HTF do you manage to break a die?   ??? ??? (split die or die nut?  ;))
Split die. Part way through cleaning the thread up, when it hit the distorted bit of thread, PING!

Split opposite the split.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 04 February 2013, 21:31:03
on the subject of repairing threads................. whats the point?  ??? surely a replacement bolt is easier? i appreciate that on ''special'' bolts like exhaust bolts it may be necesary?
Title: Re: Mechanic School Blog
Post by: Andy B on 04 February 2013, 21:32:27
ok, so its clear i shouldnt have updated tonight, not a lot of love for the easy-outs  ;D ;D ;D ;D

why do they snap? speed of use or just shit quality?

because as said, if the bolt head has sheared then it was f...ing TIGHT! And some stud extractors aren't Easy-Outs & are cheap & therefore will snap.  ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 04 February 2013, 21:34:20
ok, so its clear i shouldnt have updated tonight, not a lot of love for the easy-outs  ;D ;D ;D ;D

why do they snap? speed of use or just shit quality?

because as said, if the bolt head has sheared then it was f...ing TIGHT! And some stud extractors aren't Easy-Outs & are cheap & therefore will snap.  ;)

 :y :y :y
Title: Re: Mechanic School Blog
Post by: Andy B on 04 February 2013, 21:34:37
on the subject of repairing threads................. whats the point?  ??? surely a replacement bolt is easier? i appreciate that on ''special'' bolts like exhaust bolts it may be necesary?

Depends where it is/what it is ....... and whether it'll snap when you try to remove it. And how do you get the Easy-Out of the broken stud etc etc  ;D ;D ;D

Sometimes, just cleaning the start of the bolt will be more than good enough.  :y
Title: Re: Mechanic School Blog
Post by: YZ250 on 04 February 2013, 21:36:06
Still got a set of easy-outs from my Toolmaking days. I slated them for years but have used them twice recently with success. Removed a damaged Allen bolt from a diesel pump, where it was recessed and no access for grips, by tapping easy-out in to Allen head hole.

Like all tools, they have their uses. Just got to be sensible about where you use them, otherwise you'll end up in a bigger mess.  :y
Title: Re: Mechanic School Blog
Post by: TheBoy on 04 February 2013, 21:52:22
on the subject of repairing threads................. whats the point?  ??? surely a replacement bolt is easier? i appreciate that on ''special'' bolts like exhaust bolts it may be necesary?
a) depends if you have a replacement for said bolt
b) in this case it was the tapered part of a track rod end. Rather expensive to replace track rod end, just for a bit of effort of tidying up the thread...   ...even if it did break the die ;D

It wouldn't have just been replacement of the track rod end, it would need to go for alignment afterwards as well.
Title: Re: Mechanic School Blog
Post by: Andy B on 04 February 2013, 22:27:01
on the subject of repairing threads................. whats the point?  ??? surely a replacement bolt is easier? i appreciate that on ''special'' bolts like exhaust bolts it may be necesary?

Don't forget that there's also a thread file available in various flavours of metric & imperial http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2047675.m570.l2736&_nkw=thread+file (http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2047675.m570.l2736&_nkw=thread+file) You'd use one where just one side of the bolt/stud has been clobbered & damaged.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 05 February 2013, 19:01:23
Well, bit of a wasted day for me :( I like to move on but today I was ''floating'' helping others out as I was finished being assessed.

However I did hear some info that I'd like to discuss with you girls  8)

One of the lads reckons you can buy, although expensive, an impact gun that runs on cordless battery thats just as powerful as a compressed air impact gun.

I would really like to get one if thats the case as if i ever end up doing exhaust work and heavier work at home i'd like to be able to use it..... BUT is it as powerful in the real world as a compressed air tool?

heres what i found.... not sure this is what he means?

http://www.kingtools.co.uk/product.php/section/433/sn/DEWDC835KB
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 05 February 2013, 19:09:24
or this one even...

http://www.machinemart.co.uk/shop/product/details/clarke-cir450-24v-high-torque-cordless-impact#reviews
Title: Re: Mechanic School Blog
Post by: Andy B on 05 February 2013, 19:19:43
I'm not sure that the 14v DeWalt would be as effective as the 24v Clarke, but it'll last a lot longer. I use a DeWalt impact gun at work & it's pretty good.  :y
Title: Re: Mechanic School Blog
Post by: Entwood on 05 February 2013, 19:32:08
The important factor in shifting bolts is the max torque available ... DeWalt has just 140Nm.. the Clarke has 450 Nm .. so the Clarke is far more "powerful" ... the question is .. are the Clarke batteries any good because that sort of energy output requires some "OOMPH" ...

IMHO you need to ask the guys who use one on a regular basis what the good/bad points of each one are ... no point in loads of power and a useless battery as it will only do one bolt an hour !! and no point in the ability to do 200 bolts if you have more strength in your arm !!

key point here .. RESEARCH .. and lots of it  :)
Title: Re: Mechanic School Blog
Post by: Lazydocker on 05 February 2013, 19:37:32
As Nigel says, you need to research it and, ideally, try some out ;)

I bought a Snap-On one 13+ years ago (when they were virtually the only ones that did a decent cordless) that's pretty beefy and still going strong, although I'm sure there are better on the market now for the high price Snap-On stuff carries ;) But I got to try it out as one of the other guys had one :y
Title: Re: Mechanic School Blog
Post by: TheBoy on 05 February 2013, 19:42:21
I have the Clarke 450Nm one.

Its great with a freshly charged battery, but starts to struggle with wheelbolts when the battery is over half used, or has been left unused for months.

Also, no variable trigger on it :(
Title: Re: Mechanic School Blog
Post by: Andy B on 05 February 2013, 19:44:35
....

Also, no variable trigger on it :(

because it's an impact gun .......   ;) ;)
Title: Re: Mechanic School Blog
Post by: Lazydocker on 05 February 2013, 19:46:12
I have the Clarke 450Nm one.

Its great with a freshly charged battery, but starts to struggle with wheelbolts when the battery is over half used, or has been left unused for months.

Also, no variable trigger on it :(

Doesn't sound like the greatest then :-\ :-\

....

Also, no variable trigger on it :(

because it's an impact gun .......   ;) ;)

And? My 13YO Snap Off one has variable trigger instead of on/off as does my IR Air operated one ;)
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 05 February 2013, 19:47:40
....

Also, no variable trigger on it :(

because it's an impact gun .......   ;) ;)

Binary throttle. Sounds well-suited. ;)
Title: Re: Mechanic School Blog
Post by: Lazydocker on 05 February 2013, 19:49:35
....

Also, no variable trigger on it :(

because it's an impact gun .......   ;) ;)

Binary throttle. Sounds well-suited. ;)

Well... Yes... It could well be operator error :-X ::)
Title: Re: Mechanic School Blog
Post by: Andy B on 05 February 2013, 20:03:23
...
as does my IR Air operated one ;)

My air gun is IR too & is on or off  ;)

 ...... AFAIK that's how they work ie they keep knocking the socket round a bit further while the trigger is operated, nothing to do with how fast it initially spins, it's how long you leave it.
Title: Re: Mechanic School Blog
Post by: Entwood on 05 February 2013, 20:09:49
Reading through the descriptions of impact wrenches on those sites ... some say variable speed, others don't mention it, so I guess both types are available ...

The Dewalt has variable speed .. the Clarke does not .. or so it seems  :)
Title: Re: Mechanic School Blog
Post by: Lazydocker on 05 February 2013, 20:18:54
...
as does my IR Air operated one ;)

My air gun is IR too & is on or off  ;)

 ...... AFAIK that's how they work ie they keep knocking the socket round a bit further while the trigger is operated, nothing to do with how fast it initially spins, it's how long you leave it.

Yep, but with variable throttle you just get the turn and not the knock ;)
Title: Re: Mechanic School Blog
Post by: henryd on 05 February 2013, 20:20:09
I have a snap on 18v battery impact gun,very expensive to buy but not found anything(air powered or otherwise) that can touch it for power,mines about 5years old now but is till as good as the day I got it,just replaced one of the batterys on snap ons exchange scheme for about £60 which is around half the outright price.
I have tried other leccy and air powered guns and find they are all okay when new but just don't last,ok for weekend use but not much good used everyday :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 05 February 2013, 20:24:51
what is variable trigger? presumably so you can throttle the amount of power? so if ive got it right does that mean TB's one just does one speed? soz bit confused

ps this is bear's new tool chest  8)

a million years old but still in great cpndition especially after a good clean and a wd40 session  8)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 05 February 2013, 20:25:15
oh and the photo mght help  ::)

(http://i1226.photobucket.com/albums/ee402/webbybear1/mynewtoolchest_zps29d20b65.jpg)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 February 2013, 16:40:46
To go in bear's new toolchest....£1.40 with free delivery!!!
(http://i1226.photobucket.com/albums/ee402/webbybear1/extractors_zps94d36fb1.jpg)
Title: Re: Mechanic School Blog
Post by: Entwood on 06 February 2013, 16:57:31
To go in bear's new toolchest....£1.40 with free delivery!!!
(http://i1226.photobucket.com/albums/ee402/webbybear1/extractors_zps94d36fb1.jpg)

What are they made of at that price ?? butter ??

TBH I wouldn't trust that cheap an "easy out" ... I don't trust expensive ones much ... so I'd expect those to break PDQ .. :(

Sorry ... use them by all means .. but be very, very, wary ... IMHO
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 February 2013, 17:03:06
To go in bear's new toolchest....£1.40 with free delivery!!!
(http://i1226.photobucket.com/albums/ee402/webbybear1/extractors_zps94d36fb1.jpg)

What are they made of at that price ?? butter ??

TBH I wouldn't trust that cheap an "easy out" ... I don't trust expensive ones much ... so I'd expect those to break PDQ .. :(

Sorry ... use them by all means .. but be very, very, wary ... IMHO

Sorry Entwood, what I should have mentioned was I'm actually going to test them (well one of them). I'm going to bring home the stud block I made and turn in studs of varying torques and see what it can do  8)
Title: Re: Mechanic School Blog
Post by: ozzycat on 06 February 2013, 17:22:01
 ive found the draper ones that ive got very caperble after the abuse ive given them
Title: Re: Mechanic School Blog
Post by: Entwood on 06 February 2013, 17:25:49
No probs .. but remember this ...  the "stud block" you made is nice and new and probably still shiny, the only thing "missing" is the heads you cut off ... probably nice and square.

In real life .. the stud will have sheared as the torque imposed by the spanner was greater than the strength of the stud ... question is .. why ??   answer is probably .. rust .. the stud shank has rusted to the hole to such a degree that its resistance to movement was greater than the torque applied by the spanner .. so it broke.

In shearing the portion left behind will not be "flat" so getting the "pilot hole" central and parallel to the sides is not easy.

Add these to previous comments regarding the stud "spreading" as you force the "easy out" in ... and you'll guess why I don't like/trust the things at all.

I'm not saying don't use them .... I'm saying be very very careful in real life situations ... you can easily make things go from bad (sheared stud) to very bad ( sheared stud with easy out stuck in) to appallingly bad (sheared stud with sheared easy out stuck in).... fixing the latter is very difficult as trying to drill the easy out is near impossible on most occasions !!
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 February 2013, 17:32:20
No probs .. but remember this ...  the "stud block" you made is nice and new and probably still shiny, the only thing "missing" is the heads you cut off ... probably nice and square.

In real life .. the stud will have sheared as the torque imposed by the spanner was greater than the strength of the stud ... question is .. why ??   answer is probably .. rust .. the stud shank has rusted to the hole to such a degree that its resistance to movement was greater than the torque applied by the spanner .. so it broke.

In shearing the portion left behind will not be "flat" so getting the "pilot hole" central and parallel to the sides is not easy.

Add these to previous comments regarding the stud "spreading" as you force the "easy out" in ... and you'll guess why I don't like/trust the things at all.

I'm not saying don't use them .... I'm saying be very very careful in real life situations ... you can easily make things go from bad (sheared stud) to very bad ( sheared stud with easy out stuck in) to appallingly bad (sheared stud with sheared easy out stuck in).... fixing the latter is very difficult as trying to drill the easy out is near impossible on most occasions !!

very good points mate.
 :y
Title: Re: Mechanic School Blog
Post by: Shackeng on 09 February 2013, 18:43:38
Also, Sod's law states that the likelihood of a bolt head shearing off is in direct proportion to difficulty of access. :y
Title: Re: Mechanic School Blog
Post by: Andy B on 09 February 2013, 21:27:27
Also, Sod's law states that the likelihood of a bolt head shearing off is in direct proportion to difficulty of access. :y

Exactly!!!  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 February 2013, 12:36:04
Afternoon guys.

Again, sadly not much to discuss at the moment. on half term and just revising for my exams next week. exams split in to two.... engine, cooling, lube....followed by ignition, fuel, intake and exhaust.

there is however one thing that came up in class discussion which i'd like to discuss... and that's interference engines vs safe engines.

obviously its not great news for us if our timing belt (or tensioners) go cos we're going to have a piston/valve war. but are there any engines out there that are safe?

my teacher mentioned an old fiat punto that was safe but by the way he was talking its not something thats done anymore..... why not? wud make so much sense  :-\

 :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 February 2013, 12:37:16
ps anyone got any photos of when pistons met valves? would be cool (for me anyway) to view the carnage  :y
Title: Re: Mechanic School Blog
Post by: henryd on 15 February 2013, 12:40:30
ps anyone got any photos of when pistons met valves? would be cool (for me anyway) to view the carnage  :y

I have a 2.5 td transporter T4 here which has a broken belt,when I've pulled the head I'll try and remember to post some pictures :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 February 2013, 12:42:27
ps anyone got any photos of when pistons met valves? would be cool (for me anyway) to view the carnage  :y

I have a 2.5 td transporter T4 here which has a broken belt,when I've pulled the head I'll try and remember to post some pictures :y

nice one mate thanks  :y :y :y :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 15 February 2013, 13:00:23
Many of the older 8V engines were non interference (excluding many of the Fords, Volvos and one or two Vx). This was easy enough as valves were larger and cam lift was not so large plus lower compression ratios and the tendancy to creat combustion chambers (squish area) in the cylinder head gives clearance.

Throw in higher compresion ratios, more advanced combustion chamber design, multi valves, larger valve opening and you get much less clearance.

All simples

Plenty of pics been posted over the years of bent valves.
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 15 February 2013, 13:01:12
ps anyone got any photos of when pistons met valves? would be cool (for me anyway) to view the carnage  :y

I have a 2.5 td transporter T4 here which has a broken belt,when I've pulled the head I'll try and remember to post some pictures :y

And of the pistons  :y
Title: Re: Mechanic School Blog
Post by: Lazydocker on 15 February 2013, 13:05:29
As mark says, not as common now.

I remember one of my colleagues recovering an 8v Cavalier off the motorway with a broken cambelt. Bloke had no cover so it was a Police call out and cost him £105 (13 years ago) :o

Customer said it was toast and asked what his options were so my mate said "I'll pay the recovery cost if you sign the car over to me"

Stuck a 2nd hand belt on it and ran it up... Perfect :y Quick compression test to confirm all was OK and it was a new belt and water pump before it was passed on to his mum, whose car had just been written off :y
Title: Re: Mechanic School Blog
Post by: henryd on 15 February 2013, 14:11:49
ps anyone got any photos of when pistons met valves? would be cool (for me anyway) to view the carnage  :y

I have a 2.5 td transporter T4 here which has a broken belt,when I've pulled the head I'll try and remember to post some pictures :y

And of the pistons  :y

Last one I did pistons were ok but head was scrap,cam broken in three places and pushed up through the bearings :-X,dunno what this ones like yet,can't wait to find out :P
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 February 2013, 17:03:42
so in short it's basically cos of the more advanced engines taking up more room  :y
still would be nice to have a safe engine though...no worries with that  :y
Title: Re: Mechanic School Blog
Post by: Abiton on 15 February 2013, 17:38:00
so in short it's basically cos of the more advanced engines taking up more room  :y
still would be nice to have a safe engine though...no worries with that  :y

It is.
My Golf's tensioner started sqeaking a bit at 180-something K, no history available, may well have been the original for all I know.
"Shall I change it?" thought I, "Nah, I'll wait 'til the stem seals get a bit worse and do it then."  :)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 February 2013, 22:08:07
so in short it's basically cos of the more advanced engines taking up more room  :y
still would be nice to have a safe engine though...no worries with that  :y

It is.
My Golf's tensioner started sqeaking a bit at 180-something K, no history available, may well have been the original for all I know.
"Shall I change it?" thought I, "Nah, I'll wait 'til the stem seals get a bit worse and do it then."  :)

exactly... wait for it to go...then do it!  :y
Title: Re: Mechanic School Blog
Post by: albitz on 15 February 2013, 22:27:58
Edit - wrong thread.  :-[  ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 February 2013, 23:07:34
by the way there was another thing i wanted to discuss

i know this should be easy but i just couldnt do it  :-[ ....... and thats sharpening drill bits. i took a couple of drill bits that the teacher said needed sharpening and the angle should be 59o. sounds easy. nope! it just seemed that the 59o angle was too flat and ended up worse than before.

if im being retarded tell me and ill just keep practising  :-[

anyone else have this issue?
Title: Re: Mechanic School Blog
Post by: albitz on 15 February 2013, 23:11:50
I always break them so sharpening is something Ive never learned to do. ;D ;D
Title: Re: Mechanic School Blog
Post by: Andy B on 15 February 2013, 23:16:32
.... and ill just keep practising  :-[  ...... 

You can either sharpen a drill ..... or you can't. I know some fitters that have socks older than you  ;) & still can't sharpen one.

I can!  ;) ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 February 2013, 23:18:05
.... and ill just keep practising  :-[  ...... 

You can either sharpen a drill ..... or you can't. I know some fitters that have socks older than you  ;) & still can't sharpen one.

I can!  ;) ;)

 ;D cheers andy.... thank f... its not just me  ::)
Title: Re: Mechanic School Blog
Post by: Andy B on 15 February 2013, 23:24:06
.... and ill just keep practising  :-[  ...... 

You can either sharpen a drill ..... or you can't. I know some fitters that have socks older than you  ;) & still can't sharpen one.

I can!  ;) ;)

 ;D cheers andy.... thank f... its not just me  ::)

You need to have a go at sharpening a drill of 3/4" and bigger so you can see what you're doing. I've just been Googling but can't find what I want. A morse taper type drill has a centre in the end that helps you keep each side of the drill equal. You can sharpen a drill that only cuts on one side, and the gauge/guide helps.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 February 2013, 23:28:54
.... and ill just keep practising  :-[  ...... 

You can either sharpen a drill ..... or you can't. I know some fitters that have socks older than you  ;) & still can't sharpen one.

I can!  ;) ;)

 ;D cheers andy.... thank f... its not just me  ::)

You need to have a go at sharpening a drill of 3/4" and bigger so you can see what you're doing. I've just been Googling but can't find what I want. A morse taper type drill has a centre in the end that helps you keep each side of the drill equal. You can sharpen a drill that only cuts on one side, and the gauge/guide helps.

 :y

to give us something to do me and a couple of others are going to be making a gauge for our key rings cos we're so far ahead. its basically just an angled piece of metal (at 59o). this what you mean? or the drill bit itself?  :y
Title: Re: Mechanic School Blog
Post by: Andy B on 15 February 2013, 23:37:22
....
to give us something to do me and a couple of others are going to be making a gauge for our key rings cos we're so far ahead. its basically just an angled piece of metal (at 59o). this what you mean? or the drill bit itself?  :y

That's what I found on the net. The gauge I meant has a point that you sit the end of the drill on so that you can scribe each side of the drill on to check each side is the same ....... far too difficult to describe, far easier to show you in the metal.  :y :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 February 2013, 23:39:05
....
to give us something to do me and a couple of others are going to be making a gauge for our key rings cos we're so far ahead. its basically just an angled piece of metal (at 59o). this what you mean? or the drill bit itself?  :y

That's what I found on the net. The gauge I meant has a point that you sit the end of the drill on so that you can scribe each side of the drill on to check each side is the same ....... far too difficult to describe, far easier to show you in the metal.  :y :y

got ya mate  :y
Title: Re: Mechanic School Blog
Post by: Andy B on 15 February 2013, 23:42:20
....
to give us something to do me and a couple of others are going to be making a gauge for our key rings cos we're so far ahead. its basically just an angled piece of metal (at 59o). this what you mean? or the drill bit itself?  :y

That's what I found on the net. The gauge I meant has a point that you sit the end of the drill on so that you can scribe each side of the drill on to check each side is the same ....... far too difficult to describe, far easier to show you in the metal.  :y :y

got ya mate  :y

There was a guide in a cupboard at work. I asked a few of the lads what it was, nobody knew - even the old barstewards like myself. I'll try to remember to photo it in use. (not back in work till Tuesday though  ;) - assuming Warren B hasn't closed it by then  ???)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 February 2013, 23:44:30
....
to give us something to do me and a couple of others are going to be making a gauge for our key rings cos we're so far ahead. its basically just an angled piece of metal (at 59o). this what you mean? or the drill bit itself?  :y

That's what I found on the net. The gauge I meant has a point that you sit the end of the drill on so that you can scribe each side of the drill on to check each side is the same ....... far too difficult to describe, far easier to show you in the metal.  :y :y

got ya mate  :y

There was a guide in a cupboard at work. I asked a few of the lads what it was, nobody knew - even the old barstewards like myself. I'll try to remember to photo it in use. (not back in work till Tuesday though  ;) - assuming Warren B hasn't closed it by then  ???)

that would be really useful mate, thanks  :y
Title: Re: Mechanic School Blog
Post by: Andy B on 15 February 2013, 23:46:14
....
to give us something to do me and a couple of others are going to be making a gauge for our key rings cos we're so far ahead. its basically just an angled piece of metal (at 59o). this what you mean? or the drill bit itself?  :y

That's what I found on the net. The gauge I meant has a point that you sit the end of the drill on so that you can scribe each side of the drill on to check each side is the same ....... far too difficult to describe, far easier to show you in the metal.  :y :y

got ya mate  :y

There was a guide in a cupboard at work. I asked a few of the lads what it was, nobody knew - even the old barstewards like myself. I'll try to remember to photo it in use. (not back in work till Tuesday though  ;) - assuming Warren B hasn't closed it by then  ???)

that would be really useful mate, thanks  :y

I doubt that you'd be using morse taper drills that big in the motor trade  ;)
Title: Re: Mechanic School Blog
Post by: henryd on 16 February 2013, 00:25:45
.... and ill just keep practising  :-[  ...... 

You can either sharpen a drill ..... or you can't. I know some fitters that have socks older than you  ;) & still can't sharpen one.

I can!  ;) ;)

Me too :y
Title: Re: Mechanic School Blog
Post by: aaronjb on 16 February 2013, 10:47:19
An old fella I know (runs, owns & builds Crendon Replicas) once told me - as he sharpened a drill bit with an angle grinder w/ a slitting disc, freehand with no glasses - that the easiest way to check the angle of the end is to hold it up to a suitably sized nut.. the angle of the faces of the nut should be the same as the end of the drill.

No idea how accurate that is but the drill he sharpened certainly worked well when I used it after that!
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 February 2013, 17:32:19
Afternoon boys, hope youre all well  :y :y :y

As I mentioned previous;y me and 3 others are so far ahead we got to make a drill bit gauge with a 59 degree angle. Here's mine  8)

(http://i1226.photobucket.com/albums/ee402/webbybear1/drillbitgauge_zps5da8f3c7.jpg)

I put a 5mm hole in it and used an m6 tap to make a small thread for m6's. i also put 1cm grooves to make a little bit measurer. at the end is filed down to make a flat blade screw driver and the big hole is for my key ring.

tomorrow i'm filing a spark plug gapper and pitch gauge on it just cos i can  ;D

Exams Wednesday  :o :o :o :o :o

Also boroowed this set to do my mates french crap oil change and noticed this triangle bit  ??? what would that be for ?? (pictured below, back row, 3rd in from the left)

(http://i1226.photobucket.com/albums/ee402/webbybear1/bits_zps99679952.jpg)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 19 February 2013, 19:06:19
not worked real hard today. as said well far ahead and am twiddling my thumbs a bit. however... made an addition to the drill bit gauge... a spark plug gapper  8) 8) 8) 8)

(http://i1226.photobucket.com/albums/ee402/webbybear1/drillbt_zpsf4543e3a.jpg)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 19 February 2013, 19:07:08
...not that ill ever use it  ::) :y but still cool to have made and keep  :y
Title: Re: Mechanic School Blog
Post by: TheBoy on 19 February 2013, 19:09:56
...not that ill ever use it  ::) :y but still cool to have made and keep  :y
Its all good practice :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 19 February 2013, 19:13:27
...not that ill ever use it  ::) :y but still cool to have made and keep  :y
Its all good practice :y

had a few issues with drilling metal lately. for these gauges we're using mild steel. sometimes the drill bit goes straight through (using a pillar drill) like butter. other times (even with sharpened drill bits) it takes forever. wonder why?  :-\
Title: Re: Mechanic School Blog
Post by: Andy B on 19 February 2013, 19:28:27
.... other times (even with sharpened drill bits) it takes forever. wonder why?  :-\

Incorrect clearance on the cutting edge of the drill  ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 19 February 2013, 19:29:35
.... other times (even with sharpened drill bits) it takes forever. wonder why?  :-\

Incorrect clearance on the cutting edge of the drill  ;)

Thanks Andy. What does that mean though  :-[
Title: Re: Mechanic School Blog
Post by: Andy B on 19 February 2013, 19:34:38
.... other times (even with sharpened drill bits) it takes forever. wonder why?  :-\

Incorrect clearance on the cutting edge of the drill  ;)

Thanks Andy. What does that mean though  :-[

Easier to show you than describe.  ;) The cutting edge of the drill has to be the first & only bit of thedrill to make contact with what you're drilling. It's easy to grind a drill so that the cutting edge doesn't actually make proper contact with the metal/whatever and you're trying to drill with the face that you've just ground.

http://en.wikipedia.org/wiki/File:Drill_twist_1.jpg (http://en.wikipedia.org/wiki/File:Drill_twist_1.jpg)
Title: Re: Mechanic School Blog
Post by: martin42 on 19 February 2013, 22:04:38
your using pattern drill bits lol  ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 19 February 2013, 22:05:49
your using pattern drill bits lol  ;D ;D ;D

Don't say that Martin, Ralf'll be e-mailing me for details  ;D ;D ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: omega3000 on 19 February 2013, 22:12:45
your using pattern drill bits lol  ;D ;D ;D

 ;D ;D ;D


Many times i have been drilling with no effect , changing drill bits with no result  >:( Only to realize ive had the drill in reverse  ::) :-[ :-[
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 20 February 2013, 08:03:59
Other thing is technique, your looking to get an almost continuous length of swarf off so the drill is cutting  all the way.

Once it statrts to skid without cutting it work hardens the metal and drilling becomes much harder (and can then snap the bit)
Title: Re: Mechanic School Blog
Post by: Andy B on 20 February 2013, 10:09:12
Other thing is technique, your looking to get an almost continuous length of swarf off so the drill is cutting  all the way.

 .....

ideally, you're looking for two continuous lengths of swarf  ;)  ;)  ;) Dead easy to grind a drill so that only one side is cutting.  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 20 February 2013, 17:42:40
Other thing is technique, your looking to get an almost continuous length of swarf off so the drill is cutting  all the way.

Once it statrts to skid without cutting it work hardens the metal and drilling becomes much harder (and can then snap the bit)

so basically a VERY secure hold in the vice and a very steady drill is needed  :y

WELL......

Two exams, 2 Distinctions today  8) 8) 8) very very pleased.

There were some reet barsteward questions in the exams but I took my time and worled most of them out hence the good scores (80% and 86% respectively).

First exam was on engine mechanical (inc. diesel), lube and cooling systems. second exam was ignition, fuel, intake and exhaust.

I dont know which ones I got wrong sadly but im now grateful to get them out the way and concentrate on next sections which are chassis, brakes, suspension, tyres... and some other stuff i'm not thinking of.

Will update next week.

Happy Bear.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 20 February 2013, 18:57:28
....TRANSMISSIONS being the ''other things'' i couldn't think of  ::) quite a biggy to forget  ::) lol
Title: Re: Mechanic School Blog
Post by: Shackeng on 20 February 2013, 19:00:26
Well done Webby, it gives you a nice feeling when you do well in exams. Keep it up. :y :y :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 20 February 2013, 19:24:37
Well done Webby, it gives you a nice feeling when you do well in exams. Keep it up. :y :y :y

cheers mate  :y :y :y :y
Title: Re: Mechanic School Blog
Post by: Lazydocker on 20 February 2013, 22:49:37
Well done bear :y
Title: Re: Mechanic School Blog
Post by: henryd on 20 February 2013, 23:16:32
Nice one Webby :y :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 25 February 2013, 19:00:16
Evening boys.

As said before got so far ahead we're just asking to do whatever we want  ;D

SO, me and my buddy decided to remove/replace an entire exhaust off a T reg Toyota Avensis  :) :) :) penetrating oil works well on everything exhaust  ;D mounts, bolts, EVERYTHING  :y
(http://i1226.photobucket.com/albums/ee402/webbybear1/25feb6_zps42ef4d2b.jpg)

We then stripped the sections down and cleaned the mating surfaces. One thing I couldn't seem to get a straight answer on was if the sections had gaskets between them. So we got given ''Exhaust Paste''. Is this normal? Or a college bodge temporary repair???
(http://i1226.photobucket.com/albums/ee402/webbybear1/25feb5_zpsf0d05e90.jpg)

These were awesome bolts to get out... real easy.... these were connecting the down pipe to the next section.... why arent these bolts on throughout  :-\
(http://i1226.photobucket.com/albums/ee402/webbybear1/25feb4_zps2ab669b1.jpg)

Then we got this bad boy out  8) 8) 8) 8) with O2 socket. was expecting it was gonna need a 10ft lead pipe attached to the spanner for leverage.... but weirdly it came straight out. but i put lots of release spray. and a dab of anti-seize when i put it back ;)
(http://i1226.photobucket.com/albums/ee402/webbybear1/25feb3_zpsc6d304dd.jpg)

four wires indicating it has a heater element  8)
(http://i1226.photobucket.com/albums/ee402/webbybear1/25feb2_zps56779deb.jpg)

and finally the teacher breaks out the oscilloscope  8) 8) 8) going to be honest i understood what it was showing when we tested the o2 sensor (it went up and down 10 times in a second (or 10 secs cant quite remember) but there was a lot of messing around with the settings that confused me.  :-\
(http://i1226.photobucket.com/albums/ee402/webbybear1/25feb1_zps21e17eb3.jpg)

took it steady today. did the above, finished putting an M10X1.5 thread in to my special tool, fixed a missfire in a corsa (HT lead 3 with no resistance) and that was about it.

more updates tomorrow hopefully :)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 25 February 2013, 20:38:50
Kin ell, Fisher Price my first scope.

I would expect 02 sensor to switch about every second
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 25 February 2013, 20:42:16
Kin ell, Fisher Price my first scope.

I would expect 02 sensor to switch about every second
;D so this is shite then? they said it cost £5k!!!  :o

yeah that sounds about right.... whats it switching between? rich 'n' lean?  :-\
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 25 February 2013, 20:45:48
It switches between oxygen present and oxygen not present  :y

This can equate to lean/rich

If it had any other brand on the front it would be about a thrid of that price plus a proper scope would be a tenth.

It does do more than a scope function but in the electronics arena, the scope functionailty would be classed as 'not good enough' (as its very much aimed at noddy car electronic jobs as per its design requirement).

Title: Re: Mechanic School Blog
Post by: Webby the Bear on 25 February 2013, 20:47:41
It switches between oxygen present and oxygen not present  :y

This can equate to lean/rich

If it had any other brand on the front it would be about a thrid of that price plus a proper scope would be a tenth.

It does do more than a scope function but in the electronics arena, the scope functionailty would be classed as 'not good enough' (as its very much aimed at noddy car electronic jobs as per its design requirement).

Yeah I have noticed the price of strap-on stuff is ridonkulous!!!

They bought strap-on 3/8s ratchets for 3 of the kids for doing well.... £80 a piece... could have bought them full tool kits from halfords for that and got them really started!!!!
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 25 February 2013, 20:50:13
It switches between oxygen present and oxygen not present  :y

This can equate to lean/rich

If it had any other brand on the front it would be about a thrid of that price plus a proper scope would be a tenth.

It does do more than a scope function but in the electronics arena, the scope functionailty would be classed as 'not good enough' (as its very much aimed at noddy car electronic jobs as per its design requirement).

Yeah I have noticed the price of strap-on stuff is ridonkulous!!!

They bought strap-on 3/8s ratchets for 3 of the kids for doing well.... £80 a piece... could have bought them full tool kits from halfords for that and got them really started!!!!

I bet they didn't, Snap-On  give bits to the colleges to award as prizes....its to get them hooked and part of the 'snap-on' is best brainwashing procedure  ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 25 February 2013, 20:53:20
It switches between oxygen present and oxygen not present  :y

This can equate to lean/rich

If it had any other brand on the front it would be about a thrid of that price plus a proper scope would be a tenth.

It does do more than a scope function but in the electronics arena, the scope functionailty would be classed as 'not good enough' (as its very much aimed at noddy car electronic jobs as per its design requirement).

Yeah I have noticed the price of strap-on stuff is ridonkulous!!!

They bought strap-on 3/8s ratchets for 3 of the kids for doing well.... £80 a piece... could have bought them full tool kits from halfords for that and got them really started!!!!

I bet they didn't, Snap-On  give bits to the colleges to award as prizes....its to get them hooked and part of the 'snap-on' is best brainwashing procedure  ;D ;D ;D

wouldnt surprise me  ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: biggriffin on 26 February 2013, 14:00:43
reason snap-on is exspensive is you pay for it on the never-ever, so the agent has to make some profit, also how many new mecanics could afford to go out and spend hundereds of pounds on getting all the tools they need,when they start at a new carrear.
 know i couldnt, tools were bought every were and anywere,including snap-off, mag, etc.
 yes they are over priced,but the agents are offering a service,the prices they charge in spanky land is about 1/4 to 3/4 what you pay here, and no i dont work for them.
 you dont have to buy from them.
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 26 February 2013, 14:08:46
The sensible thing to do would be to get a small loan to buy the tools.....MUCH cheaper.  :y
Title: Re: Mechanic School Blog
Post by: biggriffin on 26 February 2013, 20:56:38
Not many 16-17 year olds would get a loan from the bank.
 my first tool box was a cantilever box givin to me by me dad and a kamasa scocket set and pliers n screwdrivers from junk sales,or borrowed.

 
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 26 February 2013, 21:21:42
Not many 16-17 year olds would get a loan from the bank.
 my first tool box was a cantilever box givin to me by me dad and a kamasa scocket set and pliers n screwdrivers from junk sales,or borrowed.

As posted in this thread my first ''tool box'' was given to me. its a proper tool chest and does me perfectly. cant really see the need for lots more space  :-\
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 26 February 2013, 21:29:36
Not many 16-17 year olds would get a loan from the bank.
 my first tool box was a cantilever box givin to me by me dad and a kamasa scocket set and pliers n screwdrivers from junk sales,or borrowed.

Maybe not twenty plus years ago but these days no problem if they have a job  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 26 February 2013, 21:55:19
Not many 16-17 year olds would get a loan from the bank.
 my first tool box was a cantilever box givin to me by me dad and a kamasa scocket set and pliers n screwdrivers from junk sales,or borrowed.

Maybe not twenty plus years ago but these days no problem if they have a job  :y

i suppose it depends where the kid works... if its in a garage then i imagine they can ''borrow'' tools that are in addition to the basic hellfrauds set (correct me if i'm wrong). if its a hobby then yeah a loan makes sense  :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 26 February 2013, 21:56:14
Maybe a business opportunity, cash-4-tools!
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 26 February 2013, 22:02:09
Maybe a business opportunity, cash-4-tools!

...makes sense as i'm now an Omega ''Lord''  :-X :-X :-X ;D ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 13 March 2013, 09:22:51
g'day sheilas. going to need some input toinight  ::) ;D ;D

we started starting systems this week. got some cool battery stuff to look at.

we looked at circuits though too. very basic for you girls but i'm confused  :'(

just leaving for school but ill update later  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 March 2013, 18:24:09
Ok boys, few things to go through today :)

Firstly sorry for the lack of updates lately but we've been on half term then review week... i'd much rather just get on with it  ::)

So. Batteries.

2 types.....
maintenance free:
(http://i1086.photobucket.com/albums/j453/Webbybear/bat1.jpg)

Conventional type (note the 6 ''cells'' on top of the battery in addition to the posts):
(http://i1086.photobucket.com/albums/j453/Webbybear/bat2.jpg)

It appears that if you have a maintenance fee battery, as per its title, theres nowt you can do if you run in to a problem where it wont maintain charge and its the battery thats faulty; bin it and get a new one!

the cpnventional type seem a lot better because the cells contain the sulphuric acid. if your problem is cos one is low, top it up with distilled water. simplez.

to test the quality of the fluid in each cell there is a battery hydrometer. when testing you're looking for consistency. if you got one cell that is down but the rest are fine the chances are you have a short circuit in that one cell and the whole batt. will need replacing.
the battery hydrometer readings per cell are:
Fully discharged - 1.130 to 1.170
Part charged      - 1.170 to 1.270
Fully charged     - 1.270 to 1.31

not sure if anyone has one at home? use it much?

to test for battery voltage, put your multimeter to DC Volts on the ''20'' scale. red lead on positive terminal, black lead on neg terminal and this will give a ''static'' reading. this should be between 12.6 and 13.2.
checking it for dynamic voltage is doing the same but when the car's running and should be around 14.2 (correct this if i'm wrong as i was rushing notes a bit).
to check for ''amp draw'' whereby you can see what ''consumers'' (things using the batt. current) you need to get into the circuit. one way to do this is to make your multimeter part of the circuit and read the amps... dosconnect either battery terminal. connect to your MM on the amps scale, join the leads to the post and the battery cable and take the reading,,,, thats how much ampage your cars using just sitting there with everything off  :y

the purpose of the battery is SLI.... starting, lighting and ignition.

so now we move on to circuits. got to be honest i was rubbish at science and even this basic stuff i'm semi-struggling with  :'( :'( :-[

Well this is what i learned.... if i have any Q's myself ill ask in red.... please put in stoopid terms though otherwise i wont get it  ::)

firstly the basic rules of electricity:

1. electricity will always look for an earth (ground).
2. it will get to earth (ground) via the quickest route.
3. if temperature increases from the current the resistance will increase too. not sure why though  :-\

voltage - ellectrical pressure
amps - electric current flow
ohms - resistance to current flow

ohms law:

''1v of electrical pressure is needed to push 1 amp of current through a resistance of 1 ohm''

so based on this theory....

(http://i1086.photobucket.com/albums/j453/Webbybear/BAT3.png)

so using the above lets look at this simple ''series circuit'' and apply the law...(sorry if this comes out really big)

(http://i1086.photobucket.com/albums/j453/Webbybear/bat4.png)

so the box looking thing being the battery supplying 12 v and the light bulb having a resistance of 2 ohms... using the triangle to work this out 12 volts divided by 2 ohms = 6 amps (i equalling amps... not sure why).

What i dont get and where this triangle doesnt seem to work is where there is 300 amps going to the starter motor supplied by a battery voltage of 12v......300 divided by 12 = 25. so does that mean theres 25 ohms of resistance at the starter?  :-\

characteristics of a ''series circuit'':
1. voltage shared between each consumer (e.g. if there was 12v and two bulbs voltage going to each would be 6v)
2. current is constant (i.e. doesnt alter if more thab one bulb)
3. one bulb goes out, all the others go out (which is why theyre not used that often in cars)

charcteristics of a ''paralell circuit'':
1. constant voltage
2. current is shared etween consumers
3. one bulb goes out, others stay on

if someone can explain the paralell circuit that would be great as again i didny understand it :(

so thats enough theory for today. head really hurting. i know you guys prob think this is very simple but i was always crap at science in school (15 years ago) and its been ages since i did it anyway. so bear with me :)

today we've been getting front and rear clusters out and testing voltage. we also checked using the MM to see if bulbs were good or bad (even if they looked ok).
how to check a singe cap, single fillament bulb...
(http://i1086.photobucket.com/albums/j453/Webbybear/bat5.png)

how to check a double cap, double fillament...
(http://i1086.photobucket.com/albums/j453/Webbybear/bat6.png)
keep your vlack lead on the earth and check one cap at a time with the red lead.

when i say ''checking'' youre just checking for continuity.... no beep equals its bad and needs changing  :y

NOW i know this is lots and as said you probably think this is silly basic.... but as said i'm struggling to get my head round stuff.... especially paralel circuits and how to work out ampage, voltage, resistance etc.

any help you can give me would be greeeeeeay  :y :y :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 18 March 2013, 20:41:49
For the ohms of the starter try 12v/300A
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 18 March 2013, 20:42:24
Oh yes, cars don't have an earth
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 18 March 2013, 20:44:12
Point three is dependent on the material, plenty of things out there where the resistance decreases with temperature, your average silicon transistor being one of them
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 March 2013, 21:33:15
For the ohms of the starter try 12v/300A

so that equation does work then mark..... equalling 0.04 ohms?
Title: Re: Mechanic School Blog
Post by: Entwood on 18 March 2013, 21:46:43
For the ohms of the starter try 12v/300A

so that equation does work then mark..... equalling 0.04 ohms?

About right .. lots of thick copper windings to produce LOTS of power with little resistance, but only for a short time ...

Power (Watts) = Volts x Amps = 12 x 300 = 3600 Watts ... 4.8 HP ...    :)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 March 2013, 21:48:02
For the ohms of the starter try 12v/300A

so that equation does work then mark..... equalling 0.04 ohms?

About right .. lots of thick copper windings to produce LOTS of power with little resistance, but only for a short time ...

Power (Watts) = Volts x Amps = 12 x 300 = 3600 Watts ... 4.8 HP ...    :)

cheers mate  :y

i think i get the principals.... struggling to understand the paralell and series circuits though  :-[
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 March 2013, 21:59:10
i believe i've had an epithany.... i feel a drawing coming on.... 5 mins plz  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 March 2013, 22:15:11
ok, series circuit...

(http://i1086.photobucket.com/albums/j453/Webbybear/bat7.png)

live through to the last bulb. voltage can only go one way so stays the same. but the bulbs need exactly the same current to draw the power (watts) to each bulb so the ampage is shared.

the parlell circuit...

(http://i1086.photobucket.com/albums/j453/Webbybear/bat8.png)

having drawn it i can clearly see that the parelell clearly has its own seperate circuit hence why if one bulb goes, the others still get the power through their own circuits. the voltage is split as its going three seperate ways. but why doesnt the ampage (current) also get shared?
Title: Re: Mechanic School Blog
Post by: Entwood on 18 March 2013, 22:43:50
It's a bit like a dual carriage way beside a single road ...  one can carry a lot more traffic than the other, parallel circuits are the same .. the electricity will take the "path of least resistance" .. literally ..

IF all the parallel circuits are IDENTICAL in resistance terms, then the current is split equally across them .. if one is "easier" then more current will go through it ...

and the voltage is NOT SPLIT .. the voltage across each one is identical at 12v the black line at 0v and the redline at 12V in your lower diagram   (theoretically in the top diagram the bit of wire between the two "bulbs" should be a different colour .. as the voltage has "dropped" after the first one and is no longer red 12v)

Try and imagine the red line is a hose pipe .. the 12v is the PRESSURE of the water, if each of your loads is a tap ... the more you open a tap the easier it is for water to flow, so more runs through the open (low resistance) tap than the shut (high resistance) ones .. the flow of water is the current. If all the taps are fully shut the pressure in the hose is at its maximum (12v in this case)

HTH :)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 18 March 2013, 22:54:17
it does. thanks mate.
stuff like this should be simple but i was rubbish at science at school  :-[
Title: Re: Mechanic School Blog
Post by: Andy B on 18 March 2013, 23:17:55
it does. thanks mate.
stuff like this should be simple but i was rubbish at science at school  :-[

Some depends on how good your teacher was at teaching .......  ;) ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 19 March 2013, 09:40:14
it does. thanks mate.
stuff like this should be simple but i was rubbish at science at school  :-[

Some depends on how good your teacher was at teaching .......  ;) ;)

lol there is that too but at school i simply had no interest especially in science. funny how later on down the line i'm learning a subject that is a huge amount to do with science... if only i'd have listened in class  ::) ;D
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 19 March 2013, 09:50:16
it does. thanks mate.
stuff like this should be simple but i was rubbish at science at school  :-[

Some depends on how good your teacher was at teaching .......  ;) ;)

I always got into trouble for correcting the Electronics teacher at school. ::) I think my demonstration of why, contrary to his teaching, you don't have ferrite cores on mains transformers was quite helpful, actually. I made one with each type of core, and when the smoke had cleared, he had learned something. ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 19 March 2013, 09:51:25
it does. thanks mate.
stuff like this should be simple but i was rubbish at science at school  :-[

Some depends on how good your teacher was at teaching .......  ;) ;)

I always got into trouble for correcting the Electronics teacher at school. ::) I think my demonstration of why, contrary to his teaching, you don't have ferrite cores on mains transformers was quite helpful, actually. I made one with each type of core, and when the smoke had cleared, he had learned something. ;D

 ;D ;D ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 19 March 2013, 12:11:37
it does. thanks mate.
stuff like this should be simple but i was rubbish at science at school  :-[

Some depends on how good your teacher was at teaching .......  ;) ;)

I always got into trouble for correcting the Electronics teacher at school. ::) I think my demonstration of why, contrary to his teaching, you don't have ferrite cores on mains transformers was quite helpful, actually. I made one with each type of core, and when the smoke had cleared, he had learned something. ;D

pmsl, losses a little to great !
Title: Re: Mechanic School Blog
Post by: Entwood on 19 March 2013, 13:27:17
Webby .. don't know if this will help at all, but is a useful aide memoire on how the elements all go together, all stem from 2 simple equations that you already know ..

V=IR (Volts = Current x Resistance) 

and

P=VI (Power = Volts x Current)

(http://imageshack.us/a/img209/4263/ohmpiechart.gif)
Title: Re: Mechanic School Blog
Post by: CaptainZok on 19 March 2013, 13:50:11
Another point to note when you start doing the calculations is make sure you have the units right Ohms, Amps, Volts and Watts. Missing a Kilo, milli or Mega is going to throw your answers out by various powers of 10.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 19 March 2013, 17:20:04
Entwood that's really handy, thanks for that... that means I simply have to input two figures (of what I know) and can easily work it out from there  :y cheers mate
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 26 March 2013, 17:55:46
This week I've been mostly doing.... ::)

BRAKES, TYRES & WHEEL BALANCING.

Brakes first of all. Well we've only done disc brakes and drums next week  :'( but disc brakes are stupidly easy.

We had to remove the pads and discs, measure them (including run out on the discs) and compare to spec and produce a report as to whether we would replace or continue to use (serviceable).

I've done brakes on 4 cars today and this was pretty much the same set up for all:

remove caliper (tie up out of the way)
remove pads
remove mounting bracket
remove disc holding bolts (if the person before remembered to put them back  ::))
remove disc
here's a pic of what the caliper bolts (blue arrows) and the mounting bracket bolts (orange)look like in situ.
(http://i1226.photobucket.com/albums/ee402/webbybear1/tyre6_zpsfd6d99b2.jpg)

now, what I do at this point is give the whole area a good clean with brake clean. wipe everything clean. you probanly don't need to every time but just for good measure I take emery cloth and lightly file the mounting bracket where the pads sit just to get the shit off.
I then take out my slide pins (ive noticed that most calipers one slide pin is in the mounting bracket and one is fioxed and part of the caliper). either way, lube them up with silicone paste...
(http://i1226.photobucket.com/albums/ee402/webbybear1/tyre7_zps2d7c8100.jpg)
now I never insist on anything and i'm always more than happy to be corrected but I wont on this!!  ;D YOU MUST USE SILICONE PASTE ON THE SLIDE PINS. END OF!  ;D
Anyway, we weren't putting new pads in so there was no need to push the piston back. however if you were putting new pads in I pinch off the brake hose using these vice grips with bits of fuel line to protect hose...
(http://i1226.photobucket.com/albums/ee402/webbybear1/tyre8_zps50a007e0.png)
...I then attach a bleed kit with tubing with a one way valve (to stop air getting in), push piston back and do up your bleed screw, unlock vice grips. DONE
So I then put a bit of copper grease where the disc will make contact with the hub.
I then put disc back, reattach mounting bracket, lube pads with copper anti seize paste where the pad touches the mount, reattach caliper, wheel back on. Pump pedal (just for good measure even though I didn't push piston back). DONE

As for measuring, well use a micrometer. pretty self explanatory. and to do the run out use a DTI whilst spinning the disc to get the run out reading.

not sure why I took a pic of this but here it is  ??? ;D
(http://i1226.photobucket.com/albums/ee402/webbybear1/tyre5_zps387119ad.jpg)

also I thought this was pretty cool showing the brake system without the body...
(http://i1226.photobucket.com/albums/ee402/webbybear1/tyre4_zps1eeb5396.jpg)


TYRES & WHEEL BALANCING

I've only done this once so I don't feel confident at doing a guide  :-[ we're doing more next week so ill reveal all then but heres the equipment
this is called breaking the bead... I think ...  :-\
(http://i1226.photobucket.com/albums/ee402/webbybear1/tyre3_zps607b7907.jpg)

getting the tyre off the rim... now I don't know if this rim is fubard following the useless kids trying to do this  :-\ but looks nackered  ;D this is actually quite tricky cos when you take the tyre off you have to get the lip on one side... and when you put it back it has to go on opposite.
(http://i1226.photobucket.com/albums/ee402/webbybear1/tyre2_zps1d044fb8.jpg)

and heres the balancing machine, really easy to use. tyre on, run it, it tells you what weight ands where to add. bash on the right weight. done
(http://i1226.photobucket.com/albums/ee402/webbybear1/tyre1_zpse7807b3c.jpg)

here's a vid of it being done by a pro though  :y :y :y
http://www.youtube.com/watch?v=8hOZXIr1ujE
Title: Re: Mechanic School Blog
Post by: Entwood on 26 March 2013, 18:15:18
Sorry Webby .. I MUST make a strong disagreement with a small, but highly important part of your post .. I'm not going to quote the whole post for one little bit .. but you say, under balancing ...

Quote
heres the balancing machine, really easy to use. tyre on, run it, it tells you what weight ands where to add. bash on the right weight. done

Absolutely and 100% WRONG !!!! - and the cause of many an argument between me and poor tyre fitters .. and I've won every argument :)

On every tyre there are little coloured dots, these represent the "light" point (yellow) and the "high" point (red). The yellow dot should be positioned by the valve (the weight of the valve compensates for the light point of the tyre). IF the wheel is marked with a "low point" (expensive wheels only) the red dot should be aligned with this.

Doing it any other way just ensures that massive amounts of un-needed weights are added to a wheel, giving further harmonic loads to an already stressed item. It also increases the risk of a weight coming off.

I could also add information about tyre "run out", colour bands and the importance of the right tyre being in the right place on the car ...

If you wish to read up on this ....

http://www.wheels-inmotion.co.uk/forum/index.php?showtopic=165

post #12 and post #1 are probably the most useful :)

HTH :)



Title: Re: Mechanic School Blog
Post by: albitz on 26 March 2013, 18:42:40
I wish I,d known all that before Sunday evening when I fitted a tyre to one of my elite alloys. ::) ;D
Will know next time though. ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 26 March 2013, 19:12:02
Sorry Webby .. I MUST make a strong disagreement with a small, but highly important part of your post .. I'm not going to quote the whole post for one little bit .. but you say, under balancing ...

Quote
heres the balancing machine, really easy to use. tyre on, run it, it tells you what weight ands where to add. bash on the right weight. done

Absolutely and 100% WRONG !!!! - and the cause of many an argument between me and poor tyre fitters .. and I've won every argument :)

On every tyre there are little coloured dots, these represent the "light" point (yellow) and the "high" point (red). The yellow dot should be positioned by the valve (the weight of the valve compensates for the light point of the tyre). IF the wheel is marked with a "low point" (expensive wheels only) the red dot should be aligned with this.

Doing it any other way just ensures that massive amounts of un-needed weights are added to a wheel, giving further harmonic loads to an already stressed item. It also increases the risk of a weight coming off.

I could also add information about tyre "run out", colour bands and the importance of the right tyre being in the right place on the car ...

If you wish to read up on this ....

http://www.wheels-inmotion.co.uk/forum/index.php?showtopic=165

post #12 and post #1 are probably the most useful :)

HTH :)

no worries mate... as long as you don't dare disagree with my silicone paste point!!!  ;D ;D ;D only kiddling.

i'll be honest we only had a 10 minute demo this morning. then a couple of goes ourselves. the teacher never mentioned the dots so I didn't know  :)

ill read the WIM thread and ask the teacxher about it too  :y :y :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 26 March 2013, 20:27:22
BTW...

I thought the Schrader valve remover tool was quite cool and would be handy. anyone know how to make a home made one? I heard someone mention using brass brake line. is this right? would be awesome to add to my drill gauge tool  8)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 26 March 2013, 20:37:33
found it  8) 8) 8)

http://www.youtube.com/watch?v=LArLXARyhAI
Title: Re: Mechanic School Blog
Post by: Andy B on 26 March 2013, 21:53:41
....

On every tyre there are little coloured dots, these represent the "light" point (yellow) and the "high" point (red). The yellow dot should be positioned by the valve (the weight of the valve compensates for the light point of the tyre). IF the wheel is marked with a "low point" (expensive wheels only) the red dot should be aligned with this.

Doing it any other way just ensures that massive amounts of un-needed weights are added to a wheel, giving further harmonic loads to an already stressed item. It also increases the risk of a weight coming off. ....

But .......  ::) when Merc fitted my tyres on the back of my car, I had the yellow dot alongside the valve on one of the tyres and I had 105 g of balance weights fitted. I took it back & got them to do it again because I wasn't happy with the amount they'd used (it felt balanced though) He returned after having put 30g on it this time to balance it ..... my yellow dot now no longer coincides with the valve  ;) ;)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 27 March 2013, 08:02:00
A big issue with tyres and balancing is that there is a working assumption that the rim is balanced before the tyre is fitted.....and there very often not!

Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 March 2013, 09:15:13
Should the rim be balanced with tyre off then?  :-\
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 27 March 2013, 09:30:03
Should the rim be balanced with tyre off then?  :-\

Its a working assumption that it is, I guess you could balance them without the tyre first (would be an interesting trial for you) and then remove metal or add heavy metal where required.
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 27 March 2013, 09:32:44
Ah yes, I forgot to mention a word of caution regarding runout.....beware as without the wheel fitted the disc is not properly clamped so the readings are pretty floored!
Title: Re: Mechanic School Blog
Post by: CaptainZok on 27 March 2013, 16:00:29
BTW...

I thought the Schrader valve remover tool was quite cool and would be handy. anyone know how to make a home made one? I heard someone mention using brass brake line. is this right? would be awesome to add to my drill gauge tool  8)
Get one bought. I'm sure the slapon man will sell you one, won't be less than a tenner. ;D ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 March 2013, 16:12:37
BTW...

I thought the Schrader valve remover tool was quite cool and would be handy. anyone know how to make a home made one? I heard someone mention using brass brake line. is this right? would be awesome to add to my drill gauge tool  8)
Get one bought. I'm sure the slapon man will sell you one, won't be less than a tenner. ;D ;D

 ;D Nar, fak that. they taught me these fabrication skills. my aim is to now make all my tools  :-X :-X :-X ;D ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 March 2013, 16:13:47
Should the rim be balanced with tyre off then?  :-\

Its a working assumption that it is, I guess you could balance them without the tyre first (would be an interesting trial for you) and then remove metal or add heavy metal where required.

ill give it a go, and compare to doing it with it on  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 March 2013, 16:14:42
Ah yes, I forgot to mention a word of caution regarding runout.....beware as without the wheel fitted the disc is not properly clamped so the readings are pretty floored!

yep no worries mate. they said if the disc screws aren't there, pop two lug nuts in to secure it  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 March 2013, 16:17:29
right, just to add... we had theory today. I didn't need to mention the coloured dot as he brought it up when we discussed balancing. the premise is....

if the tyre has a dot, mount the dot next to the shrader valve. then balance.  :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 27 March 2013, 16:19:58
Ah yes, I forgot to mention a word of caution regarding runout.....beware as without the wheel fitted the disc is not properly clamped so the readings are pretty floored!

yep no worries mate. they said if the disc screws aren't there, pop two lug nuts in to secure it  :y

Beware of that to as for instance, the favoured bolt would be a wheel bolt and they can foul on the inenr parts of the hub. Nuts should be ok.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 March 2013, 16:26:28
Ah yes, I forgot to mention a word of caution regarding runout.....beware as without the wheel fitted the disc is not properly clamped so the readings are pretty floored!

yep no worries mate. they said if the disc screws aren't there, pop two lug nuts in to secure it  :y

Beware of that to as for instance, the favoured bolt would be a wheel bolt and they can foul on the inenr parts of the hub. Nuts should be ok.

I will keep a note of that mate thanks  :y :y :y

on the run out I did was on a pug 206. the maximum run out spec is 0.05. this one had 0.20  :o :o :o would this (what to me is a small amount) really show itself during braking in the form of steering wheel vibration?
Title: Re: Mechanic School Blog
Post by: CaptainZok on 27 March 2013, 16:59:18
BTW...

I thought the Schrader valve remover tool was quite cool and would be handy. anyone know how to make a home made one? I heard someone mention using brass brake line. is this right? would be awesome to add to my drill gauge tool  8)
Get one bought. I'm sure the slapon man will sell you one, won't be less than a tenner. ;D ;D

 ;D Nar, fak that. they taught me these fabrication skills. my aim is to now make all my tools  :-X :-X :-X ;D ;D
You're not going to be a proper mechanic till you're in debt to slapon for a few grand. Our Tony's toolbox alone was £800 second hand.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 March 2013, 17:24:02
BTW...

I thought the Schrader valve remover tool was quite cool and would be handy. anyone know how to make a home made one? I heard someone mention using brass brake line. is this right? would be awesome to add to my drill gauge tool  8)
Get one bought. I'm sure the slapon man will sell you one, won't be less than a tenner. ;D ;D

 ;D Nar, fak that. they taught me these fabrication skills. my aim is to now make all my tools  :-X :-X :-X ;D ;D
You're not going to be a proper mechanic till you're in debt to slapon for a few grand. Our Tony's toolbox alone was £800 second hand.

 ;D

on a serious note, I only realised the other day after reading this thread back again and a throw away comment from someone at school that mechanics have to provide their own tools  ??? I mean, if you work for ford you have to upply the tools? I wud have thought a big company like that would have provided them  :-\
Title: Re: Mechanic School Blog
Post by: STMO123 on 27 March 2013, 17:40:14
You have to supply your own, and a home-made valve remover is not acceptable. ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 March 2013, 17:41:58
You have to supply your own, and a home-made valve remover is not acceptable. ;D

hahaha far cough ;)
Title: Re: Mechanic School Blog
Post by: CaptainZok on 27 March 2013, 20:35:35
BTW...

I thought the Schrader valve remover tool was quite cool and would be handy. anyone know how to make a home made one? I heard someone mention using brass brake line. is this right? would be awesome to add to my drill gauge tool  8)
Get one bought. I'm sure the slapon man will sell you one, won't be less than a tenner. ;D ;D

 ;D Nar, fak that. they taught me these fabrication skills. my aim is to now make all my tools  :-X :-X :-X ;D ;D
You're not going to be a proper mechanic till you're in debt to slapon for a few grand. Our Tony's toolbox alone was £800 second hand.

 ;D

on a serious note, I only realised the other day after reading this thread back again and a throw away comment from someone at school that mechanics have to provide their own tools  ??? I mean, if you work for ford you have to upply the tools? I wud have thought a big company like that would have provided them  :-\
Yep He's already spent thousands on his tools and he's not out of his time till this June. Oh and don't forget a slapon furry hat and trainers, you'll never get taken seriously without them.
Title: Re: Mechanic School Blog
Post by: STMO123 on 27 March 2013, 20:42:58
I've spent thousands on my tool, but you should see it now.  :-*
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 March 2013, 20:47:00
yours don't work does it?
Title: Re: Mechanic School Blog
Post by: Entwood on 27 March 2013, 20:47:18
I've spent thousands on my tool, but you should see it now.  :-*

Hopefully not and never .. :)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 27 March 2013, 20:48:09
I've spent thousands on my tool, but you should see it now.  :-*

Hopefully not and never .. :)

+ everyone. in the world. ever
Title: Re: Mechanic School Blog
Post by: STMO123 on 27 March 2013, 20:54:30
I've spent thousands on my tool, but you should see it now.  :-*

Hopefully not and never .. :)

+ everyone. in the world. ever
Gayboy loves it.
Title: Re: Mechanic School Blog
Post by: Andy B on 27 March 2013, 22:04:00
.....

yep no worries mate. they said if the disc screws aren't there, pop two lug nuts in to secure it  :y
....

yet more Americanisms  :(  :(  :(  :(  :(

on the run out I did was on a pug 206. the maximum run out spec is 0.05. this one had 0.20  :o :o :o would this (what to me is a small amount) really show itself during braking in the form of steering wheel vibration?

0.2mm/ 8thou"? Yes, you'll most definitely feel that much  ;)
Title: Re: Mechanic School Blog
Post by: Nick W on 27 March 2013, 23:07:34
BTW...

I thought the Schrader valve remover tool was quite cool and would be handy. anyone know how to make a home made one? I heard someone mention using brass brake line. is this right? would be awesome to add to my drill gauge tool  8)

Do you mean the gadget to unscrew the valve core? They're dirt cheap, although I've made a couple as I needed them late on a Sunday evening. One is from 1/4" hex bar, and is for use in multi tip screwdrivers. The other was turned from a length of 1/2" brass bar, knurled on the end, and with a slot cut in the other end. Worked great, took up no space and looked cool - which is important for home-made tools! Wish I hadn't lost it somewhere.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 28 March 2013, 13:07:23
BTW...

I thought the Schrader valve remover tool was quite cool and would be handy. anyone know how to make a home made one? I heard someone mention using brass brake line. is this right? would be awesome to add to my drill gauge tool  8)

Do you mean the gadget to unscrew the valve core? They're dirt cheap, although I've made a couple as I needed them late on a Sunday evening. One is from 1/4" hex bar, and is for use in multi tip screwdrivers. The other was turned from a length of 1/2" brass bar, knurled on the end, and with a slot cut in the other end. Worked great, took up no space and looked cool - which is important for home-made tools! Wish I hadn't lost it somewhere.

yes, sorry nick that is what i meant  :y

thats the thing.... those tools are like 98p. but i like the satisfaction of making it myself and it looking cool  ;D :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 28 March 2013, 13:10:56
BTW...

I thought the Schrader valve remover tool was quite cool and would be handy. anyone know how to make a home made one? I heard someone mention using brass brake line. is this right? would be awesome to add to my drill gauge tool  8)
Get one bought. I'm sure the slapon man will sell you one, won't be less than a tenner. ;D ;D

 ;D Nar, fak that. they taught me these fabrication skills. my aim is to now make all my tools  :-X :-X :-X ;D ;D
You're not going to be a proper mechanic till you're in debt to slapon for a few grand. Our Tony's toolbox alone was £800 second hand.

One born every minute plus the slap-on warranty on the tool boxes is not the best  :y
Title: Re: Mechanic School Blog
Post by: CaptainZok on 28 March 2013, 15:57:30
BTW...

I thought the Schrader valve remover tool was quite cool and would be handy. anyone know how to make a home made one? I heard someone mention using brass brake line. is this right? would be awesome to add to my drill gauge tool  8)
Get one bought. I'm sure the slapon man will sell you one, won't be less than a tenner. ;D ;D

 ;D Nar, fak that. they taught me these fabrication skills. my aim is to now make all my tools  :-X :-X :-X ;D ;D
You're not going to be a proper mechanic till you're in debt to slapon for a few grand. Our Tony's toolbox alone was £800 second hand.

One born every minute plus the slap-on warranty on the tool boxes is not the best  :y
I've told him time and again Mark but his dealer turns up every Wednesday with the van. He's not been spending much lately as he's at college on Wednesdays till he finishes in June.
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 28 March 2013, 16:02:37
He sounds like the mechanic worlds equivalent of a drug dealer!
Title: Re: Mechanic School Blog
Post by: CaptainZok on 28 March 2013, 16:07:37
Think his latest purchase was a slapon furry trappers hat for the cold weather. He won't tell me what it cost him.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 02 April 2013, 15:28:57
Afternoon gays. hope youre all well and enjoying the sunshine (assuming you too have the sun  :-\)

Anyway, we're on holiday....AGAIN!!! Seriously this holiday thing sucks. it feels like we've been there 5 mins and we're having a break already  >:(

I spoke to the teacher and very sadly we're not touching anymore electrics for this level.  :'( :'( :'( its a real shame cos I thought I was really starting to get to grips with it especially the wiring diagrams.

SO. its time for me to do some self teaching and try and muddle my way through.

i posted a thread about electric diagnosis and i felt i didn't really get my point across (nowt to do with you... me not explaining myself properly.) so i'm going to try here and re-explain what i meant with a mock problem of parking sensors not working (ive sorted this on my car... just needed cleaning but for the sake of completeness...)

ok so you wake up one day and your parking sensors aint working. the process from an ELECTRICAL FAULT FINDING point of view (my queries in red as usual) :y....

remove and check sensor is this a continuity check? i.e. no continuity = bad sensor
.
.
.
if faulty, replace.
.
.
.
if not faulty then locate and check fuse
.
.
.
if fuse bad, replace fuse
.
.
.
if fuse good, then do voltage test from connector of parking sensor to a good earth (ground) whilst working the parking sensor (i.e. pop in reverse or to a point where the sensor should work)
.
.
.
if no voltage present then i think(?) you'd have to trace the wiring back and look for a short or open circuit - correct?
.
.
.
if voltage present then check voltage at fuse with it plugged in
.
.
.
if no voltage present at fuse then the open/shorted circuit is between this and the switch (assuming the switch is after the fuse) - look for that by following the wiring
.
.
.
if fuse voltage present then check voltage at switch
.
.
.
if no voltage there then switch is bad and replace
.
.
.
all faults fixed (or should be)

this is what i tried to do in the first place (i.e. give a very simple/basic step by step guide that would work in general for most electric fault finding)


if you agree with what ive put...then the next thing i need to know..... how on earth do you trace wiring wen looking for shorts/opens? wiring seems to just disappear in to the unknown.

discuss  :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 02 April 2013, 16:06:30
I woudl say no.

For me, I would be doing the following.

Check reverse light illuminates.

Check connections on reverse parking controller.

Check for volts at the parking sensor controller when reverse is engaged.

From that point on your in the hands of the suppliers ecu fault finding (as continuity test on a parking sensor wont tell you a great deal)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 02 April 2013, 16:31:10
I woudl say no.

For me, I would be doing the following.

Check reverse light illuminates.

Check connections on reverse parking controller.

Check for volts at the parking sensor controller when reverse is engaged.

From that point on your in the hands of the suppliers ecu fault finding (as continuity test on a parking sensor wont tell you a great deal)

Fair enough, Mark  :y

Will my fault finding guide help in any other situation as I think the P.Sensor's prob a bad example  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 09 April 2013, 18:03:16
Well still on fekking holiday  >:( >:( >:( >:(

HOWEVER, I know I'm sad but I'm really looking forward to getting my multi meter which should be here tomorrow. Sooooo many things even though it's only a very basic one. Like Mark's Hornby said ''Fisher Price - My first DVOM''  ;D ;D ;D ;D

First thing to do is to check all these HT leads I got for the correct resistance on my Omega as I seem to have caused a misfire or very much sounds like a mis   :( however I'm sort of glad cos it gets me to use all the knowledge I've gained so far. hopefully ill get it sorted though :y

this being the one I bought. cheers for the tip guys  :y :y :y

(http://i1226.photobucket.com/albums/ee402/webbybear1/dvom_zps1ba00c27.jpg)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 10 April 2013, 20:08:25
Whilst on holiday i'm filling the time talking about, well, 'dangle berries' really  ::)

got these in the post. forgot i'd ordered them as it took ages to get here from the states. theyre anti fog which will be good as I sweat like a beatch and they cloud up normally  >:(

only cost $8 US. $6 extra for postage - will post the link if anyones interested. just means I wont have to wear the ones at school that are covered in, well, shite!  ::)
(http://i1226.photobucket.com/albums/ee402/webbybear1/dewalt_zps7ae3f684.jpg)

(http://i1226.photobucket.com/albums/ee402/webbybear1/dewalt2_zpse0cc2f31.jpg)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 10 April 2013, 20:09:20
$7 even  ::)
Title: Re: Mechanic School Blog
Post by: ozzycat on 10 April 2013, 20:27:43
$7 even  ::)
do they do ones that go over glasses webby
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 10 April 2013, 20:31:39
$7 even  ::)
do they do ones that go over glasses webby

an excellent question as I too wear glasses. mainly for driving though.

these do go over my glasses....... just  ::)
Title: Re: Mechanic School Blog
Post by: Andy B on 10 April 2013, 21:26:11
I've never yet paid for my own PPE .... mine aren't branded though  ;) ;) ;)
Title: Re: Mechanic School Blog
Post by: CaptainZok on 10 April 2013, 21:33:48
I've never yet paid for my own PPE .... mine aren't branded though  ;) ;) ;)
And so you shouldn't, employers duty to supply.
Not your fault if you forget to take em off till you get home is it.
Title: Re: Mechanic School Blog
Post by: Andy B on 10 April 2013, 21:35:58
....
Not your fault if you forget to take em off till you get home is it.

You've been in the same dilemma .......  ::) ::) ::)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 10 April 2013, 23:09:51
yeah the school do supply them. but theyre in a big box and not cleaned and have been worn by grotty teenagers with god knows what kind of diseases (sexual or other). and TBH it was the fact theyre just normal ones and I being a sweaty, fat, furry nacker need the anti fog option so I can see what im doing  ::) :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 10 April 2013, 23:42:11
Although be aware those are not suited to grinding etc
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 April 2013, 19:32:24
New multimeter  8) 8) 8) 8) 8) 8) 8) £1.39!!!!

and its pocket sized  8) 8) 8)

(http://i1226.photobucket.com/albums/ee402/webbybear1/mm1_zpsad57ded0.jpg) (http://s1226.photobucket.com/user/webbybear1/media/mm1_zpsad57ded0.jpg.html)
(http://i1226.photobucket.com/albums/ee402/webbybear1/mm2_zpsd48a450e.jpg) (http://s1226.photobucket.com/user/webbybear1/media/mm2_zpsd48a450e.jpg.html)
Title: Re: Mechanic School Blog
Post by: ozzycat on 11 April 2013, 20:08:08
get back to school you mitcher ;D :D :D :D :D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 April 2013, 20:21:12
get back to school you mitcher ;D :D :D :D :D

lol wish I was mate  ::) ;D ;D
Title: Re: Mechanic School Blog
Post by: ozzycat on 11 April 2013, 20:44:25
get back to school you mitcher ;D :D :D :D :D

lol wish I was mate  ::) ;D ;D
how long you off for
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 April 2013, 20:49:56
get back to school you mitcher ;D :D :D :D :D

lol wish I was mate  ::) ;D ;D
how long you off for

back on Monday thank god... get away from the wife, the step kids and the house  ::) ;D
Title: Re: Mechanic School Blog
Post by: ozzycat on 11 April 2013, 21:00:24
get back to school you mitcher ;D :D :D :D :D

lol wish I was mate  ::) ;D ;D
how long you off for
not too bad ...you could go and cheer emd up hes  abit down in the dumps at the mo

back on Monday thank god... get away from the wife, the step kids and the house  ::) ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 11 April 2013, 21:14:45
why whats up with him  ???
Title: Re: Mechanic School Blog
Post by: ozzycat on 11 April 2013, 22:26:56
why whats up with him  ???
il pm you
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 April 2013, 18:13:12
Finally back to school  8) 8) 8) so let's get down to it...

brake drums today...

these as you probably already know are usually found in the rear. you release the handbrake and slacking off the handbrake cable. you take the wheel off and in the case of the car I worked on ('97 Renault megan) you break loose and remove the axel nut as this is securing the brake drum to the hub assembly.
Take off the drum.
you will be faced with what I felt was the most complicated looking thing in the world  :D :D :D :D
in short though the two brake shoes are on either side. I undid the two securing pins in the middle, prised the spring off that held the handbrake leaver to the right hand shoe and with the tension off the whole assembly everything came out quite easily.
you must however take a photo of everything unless you are Rain Man and can remember how it all went back together.

this is a pic of the shoes out. one is still attached to the handbrake cable and I just popped this loose....
(http://i1226.photobucket.com/albums/ee402/webbybear1/drums1_zps69c97c61.jpg) (http://s1226.photobucket.com/user/webbybear1/media/drums1_zps69c97c61.jpg.html)
Also in this pic you can see 6 little oval areas where the brake shoes sit. I cleaned these up with a small file and emery cloth and before replacement applied copper anti-seize paste.

this is of it all back together  :y
(http://i1226.photobucket.com/albums/ee402/webbybear1/drums2_zps2e0a8e94.jpg) (http://s1226.photobucket.com/user/webbybear1/media/drums2_zps2e0a8e94.jpg.html)

When I put it back together I found the easiest way was to attach the bottom shoes together with the small spring and use the shoes for leverage to slot them in to position. the big top spring was a bit of a pain but I overcame this with a pair of pliers.

At this point you should also use the handbrake adjuster to back off the cable so you can fit the drum back on. keep doing it up until you have a bit of resistance when spinning the drum. tighten your handbrake cable. job jobbed  :y :y :y

there is a ''leading'' and a ''trailing'' shoe. the leading shoe is towards the front of the car and is the one that takes the most wear.

when working out whether you need new ones..... measure the friction material and compare to spec. measure the diameter of the brake drum and compare to spec.

I found it was challenging at times especially for my first go. but alls well that ends well  :y
Title: Re: Mechanic School Blog
Post by: STMO123 on 15 April 2013, 18:20:43
Oh yes. I've seen a few of those springs disappear under 'things'. ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 April 2013, 18:22:18
Oh yes. I've seen a few of those springs disappear under 'things'. ;D

That reminds me... I wore my new safety glasses all day. they've already saved my eyes!!!  :o I had a spring fire off in to my face and ricochet off my glasses  :o :o :o :o :o
Title: Re: Mechanic School Blog
Post by: TheBoy on 15 April 2013, 18:23:39
Oh boy, Webby, are you going to enjoy doing your Omega handbrake. NOT!!!!!

Frakking 'orrible things
Title: Re: Mechanic School Blog
Post by: Andy B on 15 April 2013, 18:24:03
....
there is a ''leading'' and a ''trailing'' shoe. the leading shoe is towards the front of the car and is the one that takes the most wear.
 .....

Also available .......  twin leading shoes  ;)  ;)  ;)

http://www.retroanaconda.com/landrover/wp-content/uploads/2010/04/DSC01173.jpg  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 April 2013, 18:25:45
....
there is a ''leading'' and a ''trailing'' shoe. the leading shoe is towards the front of the car and is the one that takes the most wear.
 .....

Also available .......  twin leading shoes  ;)  ;)  ;)

http://www.retroanaconda.com/landrover/wp-content/uploads/2010/04/DSC01173.jpg  :y

oh yeah forgot that.... two cylinders top and bottom. its also worth noting that those cylinders I believe have mini pistons inside which is what pushes the shoe against the drum when braking  :y
Title: Re: Mechanic School Blog
Post by: Andy B on 15 April 2013, 18:27:10
....
oh yeah forgot that.... two cylinders top and bottom. its also worth noting that those cylinders I believe have mini pistons inside which is what pushes the shoe against the drum when braking  :y

They do indeed & make a mess inside your drums when they leak.  ???  ;)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 April 2013, 18:28:42
....
oh yeah forgot that.... two cylinders top and bottom. its also worth noting that those cylinders I believe have mini pistons inside which is what pushes the shoe against the drum when braking  :y

They do indeed & make a mess inside your drums when they leak.  ???  ;)

 :y :y :y

ok, million dollar question  :D

why do some have drums and why do some have all discs like the miggy?
Title: Re: Mechanic School Blog
Post by: TheBoy on 15 April 2013, 18:30:24
Omega has drums for handbrake ;)
Title: Re: Mechanic School Blog
Post by: Andy B on 15 April 2013, 18:33:10
In the beginning ........ cars used used to have drum brakes front & back - that's (almost) all there was, & you were if fortunate if they were hydraulically operated, some used to have rod operated brakes.  :o :o :o :o

Discs are more efficient & were adopted as cars got faster & heavier, however they are crap as a handbrake, hence, a lot of cars like the Omega, having a disc/drum set up at the back.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 April 2013, 18:33:28
Omega has drums for handbrake ;)

shoes behind the discs in the hub assembly? ive never took mine out  ::) ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 April 2013, 18:34:23
In the beginning ........ cars used used to have drum brakes front & back - that's (almost) all there was, & you were if fortunate if they were hydraulically operated, some used to have rod operated brakes.  :o :o :o :o

Discs are more efficient & were adopted as cars got faster & heavier, however they are crap as a handbrake, hence, a lot of cars like the Omega, having a disc/drum set up at the back.

got ya - cheers andy  :y :y :y
Title: Re: Mechanic School Blog
Post by: Andy B on 15 April 2013, 18:35:29
Omega has drums for handbrake ;)

shoes behind the discs in the hub assembly? ive never took mine out  ::) ;D

I've had 2 Senator & this Omega covering 20 years ...... I've yet to see - or had need - to see inside the handbrake drum  ;)
Title: Re: Mechanic School Blog
Post by: TheBoy on 15 April 2013, 18:36:59
Omega has drums for handbrake ;)

shoes behind the discs in the hub assembly? ive never took mine out  ::) ;D
Indeed. I hate 'em
Title: Re: Mechanic School Blog
Post by: TheBoy on 15 April 2013, 18:38:08
Omega has drums for handbrake ;)

shoes behind the discs in the hub assembly? ive never took mine out  ::) ;D

I've had 2 Senator & this Omega covering 20 years ...... I've yet to see - or had need - to see inside the handbrake drum  ;)
Annual task on the Bullet, bloody thing. No idea why. Even that DTM fella has stripped them, then immediate failed MOT on efficiency ;D
Title: Re: Mechanic School Blog
Post by: albitz on 15 April 2013, 18:39:06
I have so far managed to avoid any contact with them on my senator and my Omegas. :)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 15 April 2013, 18:39:48
Omega has drums for handbrake ;)

shoes behind the discs in the hub assembly? ive never took mine out  ::) ;D
Indeed. I hate 'em

ive looked at the guide. does look a mare  ::)
Title: Re: Mechanic School Blog
Post by: Andy B on 15 April 2013, 18:40:04
....
Annual task on the Bullet, bloody thing. No idea why. Even that DTM fella has stripped them, then immediate failed MOT on efficiency ;D

So much for 'use it or lose it' then  ::)  ::)  ::) My handbrake get used EVERY year at MOT time  ;D  ;D  ;D  ;D
Title: Re: Mechanic School Blog
Post by: Andy B on 15 April 2013, 18:40:48
I have so far managed to avoid any contact with them on my senator and my Omegas. :)

you mean you use Park like every other auto driver  ;D  ;D  ;D  ;D
Title: Re: Mechanic School Blog
Post by: TheBoy on 15 April 2013, 18:42:04
I have so far managed to avoid any contact with them on my senator and my Omegas. :)

you mean you use Park like every other auto driver  ;D  ;D  ;D  ;D
As did I for the first couple of years...  ...it was when it started failing that I started using it, and I do now religiously
Title: Re: Mechanic School Blog
Post by: Andy B on 15 April 2013, 18:43:18
.. and I do now religiously

You mean you pray it's still there where you left it  ;)  ;)  ;)
Title: Re: Mechanic School Blog
Post by: STMO123 on 15 April 2013, 19:06:30
My new purchase has drums at the rear. A lot of focus's (new ones) do too.
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 16 April 2013, 08:04:17
Got a series Land Rover on the drive wanting new front shoes and cylinders, bloody awful setup!
Title: Re: Mechanic School Blog
Post by: Taxi_Driver on 16 April 2013, 18:36:35
....
Annual task on the Bullet, bloody thing. No idea why. Even that DTM fella has stripped them, then immediate failed MOT on efficiency ;D

So much for 'use it or lose it' then  ::)  ::)  ::) My handbrake get used EVERY year at MOT time  ;D  ;D  ;D  ;D

Must admit.....in the 3 years i owned my 2.2, i never used the handbrake.....it always passed the MOT.....in fact i think it was the only thing that didnt go wrong with it  ;D ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 23 April 2013, 22:04:10
G'day boys, hope you're all loooving the extra warm weather  8) it's certainly been a tad warm in the workshop this week  :o :o :o ::)

Anyhow, I don't really see taking much more about the brakes as I've covered most of what we've learned already. however I would like to quickly talk about brake servos. I didn't realise that if there was no brake servo (a line from the master cylinder to the air intake using the vacuum created to help pressurise the brake fluid) then it would be virtually impossible to depress the brake pedal hard enough to brake. interesting! In addition the actual length of the pedal is there to ease drivers' effort.... if you think about it it does makes sense as your using torque (leverage + force) to aid the driver :)

Ok down to the stuff we've been doing this week and I have found it VERY interesting...

STEERING:

This week we mostly been looking at rack and pinion racks  :D

This is a power steering rack (note the metal lines which are for power steering fluid. note also the track rod ends are attached in this photo)
(http://i1226.photobucket.com/albums/ee402/webbybear1/steering5_zpsaa1edb67.jpg) (http://s1226.photobucket.com/user/webbybear1/media/steering5_zpsaa1edb67.jpg.html)
the operation of the steering rack is very, very simple. the 'pinion gear' is what you see coming down in to the rack. when this is spun round (by connection to the steering wheel) this gear moves the ''rack'' gear left or right...this is connected to the hub via the track rod ends and affects its left to right motion by pushing the hub inwards and outwards.
from an alignment point of view it is important to note that in most cases the steering rack is positioned behind the centre point of the hub.... as per my awesome paint picture  8)
(http://i1226.photobucket.com/albums/ee402/webbybear1/steering7_zpsad11ea51.png) (http://s1226.photobucket.com/user/webbybear1/media/steering7_zpsad11ea51.png.html)

......but we'll come nore on to the alignment in a few  8)

Anyhow sadly we weren't allowed to take a rack out of a car  :'( that sucked cos I know that theyre hard to do and I really fancied the challenge. but nevertheless we were tasked woth removing and replacing a track rod end.
jack up, support on stands, remove wheel.
undo the nut securing the track rod end in place. then undo the nut on top of the ball joint and use a ball joint chisel....
(http://i1226.photobucket.com/albums/ee402/webbybear1/steering8_zps3abc82e4.jpg) (http://s1226.photobucket.com/user/webbybear1/media/steering8_zps3abc82e4.jpg.html)
....to separate the ball joint and relieve it of its' place in the hub assembly. (chisel is wedge shaped so as you hammer it in, it separates further)

a pic of the balljoint clearly protruding from the steering rack and attaching to the hub assembly...
(http://i1226.photobucket.com/albums/ee402/webbybear1/steering6_zps022c5b48.jpg) (http://s1226.photobucket.com/user/webbybear1/media/steering6_zps022c5b48.jpg.html)

a pic of the one on the Renault Migraine Megane that I did...
(http://i1226.photobucket.com/albums/ee402/webbybear1/STEERING3_zps5ad44c47.jpg) (http://s1226.photobucket.com/user/webbybear1/media/STEERING3_zps5ad44c47.jpg.html)

a pic of the tie rod twisted off and ball joint knocked out (note the pic is of it resting on the control arm in case you're wondering about its' odd orientation. and soz for bad photos  ::))
(http://i1226.photobucket.com/albums/ee402/webbybear1/steering9_zpsc31c502f.jpg) (http://s1226.photobucket.com/user/webbybear1/media/steering9_zpsc31c502f.jpg.html)

before you get to this point you would have held the road wheel (with it attached obviously) and shook it to look for play. if there is any is probably this track rod end. when track rod end off look for cuts in the rubber boot (or gaiter) and press it in and move it around and look for ease of/excessive play. if so REPLACE  :y

We also removed and replaced the gaiters (rubber boots) on the steering rack with them in situ. look for cuts or wear. if needed to replace. not much to say about that really other than use side cutters to break the metal clip and pull gaiter off. I suppose you should replace the metal securing rings/clips but we used cable ties. is that acceptable in your opinions???

as I said I really wish theyd let us actually pull a rack  :'( but now to the fun bit  :) :) :) :) :) :) :) :)

TOE ALIGNMENT

This, as far as I can work out is specifically the alignment of these track rod ends that attach to the steering rack. note I haven't touched the camber adjustment yet  :y

firstly I need to explain degrees and minutes. you know what a degree is in terms of angles (surely?  :-\ ::) ;D). minutes are a fraction of 1 degree and there are 60 minutes in a degree... very small angles i'm sure you'll appreciate. I should also explain that toe out is referred to as ''negative'' toe and toe in is referred to as ''positive'' toe.

ok so generically speaking when talking about what the track rod ends do (at the front of the car)..... RWD cars tend to toe out i.e. when the power comes on they want to push outwards. FWD cars tend to toe in i.e. the wheels wants point inwards. This is reflected in the toe settings...

Title: Re: Mechanic School Blog
Post by: Webby the Bear on 23 April 2013, 22:05:04
CONT...

A spec (from Autodata) for a FWD Corsa 1.6 I had to do was ''0 degrees + 10 minutes N +/- 10 minutes''. this shows that when pointing forward they should be 0 degrees (i.e, parallel) + 10 minutes negative with the tolerance being +/- 10 minutes.

So with the corsa settings you can see that they want it set up to toe out slightly to compensate for the fact that, as a FWD car, it will naturally want to toe in when driving. I hope you understand that...if not i'm confident that someone like mark/andyb/entwood etc will be able to explain it better than me  :y but fortunately I do totally understand it  :y

an easy way to view it is to use a table (like the one below). note on there your spec and your initial reading and youll be able to see how much you need to move it and give you a good sense of where you are...
(http://i1226.photobucket.com/albums/ee402/webbybear1/steering10_zps8ea1edb8.png) (http://s1226.photobucket.com/user/webbybear1/media/steering10_zps8ea1edb8.png.html)
as a very rough guide if youre having to adjust the toe by 1 degree or more... you've had a big problem!

ok, so now comes to setting the toe angle  :D :D :D :D :D :D...................... :D :D :D :D :D :D :D

by no means is it difficult...but I put a lot of cheesy faces cos I think its a bit of a dark art and despite my teachers' assurance that the gauges we've got are accurate I doubt them very much. of course I cold be wrong and they may be fantastically correct. let me know what you think but I think its a hack way of doing it and to me its inaccurate. but as said we'll see what the experts on her think  :y

Anyway.... to the set up...
(http://i1226.photobucket.com/albums/ee402/webbybear1/STEERING1_zpsecadaa2c.jpg) (http://s1226.photobucket.com/user/webbybear1/media/STEERING1_zpsecadaa2c.jpg.html)
in short you set one side up against the rim of the car. match that up to the other side.
you then set them up so the mirror side I on the N/S front wheel and the one with the viewing tube is on the O/S front wheel. you look in the viewing tube and adjust the little dial to get the triangle lined up...once lined up look at your gauge and it will show you how much you're out by.

this next bit is important and fekking difficult to explain......

if, after taking your initial reading, you need to toe out to get it in to spec you would need to shorten the track rod and you would need to turn the track rod anti clock wise.

if you need to toe in you'll need to lengthen the track rod and turn it anti clockwise.

this is all because of the track rod sitting behind the centre point of the hub and therefore its that that dictates how you move the tie rod. ..... as its sat behind lengthening toes in, shortening ties out.

soz I know my explanations shite but ill have a think and try to explain it better.

Well in addition to the above we took apart a steering rack. pretty cool. and FULL of grease. here's a pic of the rack gear shaft :)
(http://i1226.photobucket.com/albums/ee402/webbybear1/STEERING2_zpse9f7e9f1.jpg) (http://s1226.photobucket.com/user/webbybear1/media/STEERING2_zpse9f7e9f1.jpg.html)

Anyway look forward to the comments on quite a bulky post. :):):)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 23 April 2013, 22:13:31
OMG just noticed in that last photo josh was sticking his finger up  ;D ;D ;D little b*****d! i'll smack him tomorrow for that  >:( >:( ::) ;D

one thing I shoulda mentioned..... before you unscrew the track rod end...count the threads that are showing. therefore youll get it about right when you refit it.... although you will for sure need an alignment  :y
Title: Re: Mechanic School Blog
Post by: henryd on 23 April 2013, 23:03:18
Same set of tracking gauges that I have,old but do the job :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 23 April 2013, 23:07:27
Same set of tracking gauges that I have,old but do the job :y

Fair play mate. The reason I couldn't see them being accurate is cos when lining the pins up to the rim its not accurate at all. in fact it was more of ''if each pin touches the edge of the rim that's ok..... but how can it be when the tolerances we're talking about are 1/60 of a degree  :o

 :y
Title: Re: Mechanic School Blog
Post by: symes on 23 April 2013, 23:08:58
Same set of tracking gauges that I have,old but do the job :y
I got a set like that too-ok but not as good as laser-however they were free :y
Title: Re: Mechanic School Blog
Post by: Andy B on 23 April 2013, 23:16:04
.....
I didn't realise that if there was no brake servo (a line from the master cylinder to the air intake using the vacuum created to help pressurise the brake fluid) then it would be virtually impossible to depress the brake pedal hard enough to brake.....

Not quite true. If you've ever been towed in your Omega, you'll realise how much more force is needed to stop your car when there's no vacuum assistance (likewise your steering is difficult because of the lack of assistance - but not all cars have power steering  ;)). The Omega's brakes were designed with a servo in mind ...... but when the world was in black & white it was quite common for a car not to have servo'd brakes. These brakes worked OK in normal use because they designed to work without a servo, but you had to shove the pedal a bit harder yourself because of course there wasn't any assistance.
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 24 April 2013, 10:31:49
My Westfield doesn't have servo brakes. Ok, it's 1/3rd the weight of an Omega but the pedal's still reasonably light. Depends on the ratio of master and slave cylinder diameters and also the leverage of the pedal as it acts on the master cylinder.
Title: Re: Mechanic School Blog
Post by: Andy B on 24 April 2013, 11:03:47
My Westfield doesn't have servo brakes. Ok, it's 1/3rd the weight of an Omega but the pedal's still reasonably light. Depends on the ratio of master and slave cylinder diameters and also the leverage of the pedal as it acts on the master cylinder.

Thinking about it, neither does SWMBO's Smart Roadster .......   :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 24 April 2013, 12:22:48
This bloody Land Rover does not ahve Sevo brakes either.....even if it did they would still be rubbish  ;D

On the wheel alignment, on the optical setups I always put them together (rim tips to rim tips) and check that they read a zero toe angle as a quick check for accuracy before use as they can get bent and damaged!

They are pretty accurate though (assuming the wheel rims are oka dn the alloy/rim is not buckled!)

Also make sure the steering rack/box is centred before any adjustment
Title: Re: Mechanic School Blog
Post by: omega3000 on 24 April 2013, 14:26:17
OMG just noticed in that last photo josh was sticking his finger up  ;D ;D ;D little b*****d! i'll smack him tomorrow for that  >:( >:( ::) ;D

one thing I shoulda mentioned..... before you unscrew the track rod end...count the threads that are showing. therefore youll get it about right when you refit it.... although you will for sure need an alignment  :y

You can do that but i always count the turns or you can put some tape on the thread as a marker , never had any problem with wheel alignment after  :) Having a wheel alignment will of course confirm any adjustment needed but im a tight git and never do  :P ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 24 April 2013, 15:04:08
This bloody Land Rover does not ahve Sevo brakes either.....even if it did they would still be rubbish  ;D

On the wheel alignment, on the optical setups I always put them together (rim tips to rim tips) and check that they read a zero toe angle as a quick check for accuracy before use as they can get bent and damaged!

They are pretty accurate though (assuming the wheel rims are oka dn the alloy/rim is not buckled!)
Also make sure the steering rack/box is centred before any adjustment

Then I stand corrected  :y I just thought that with the fact that youre just eyeballing the rim tips it cant be that accurate.

one other thing where I feel its not very good is this..... say you have to toe in to get the setting in to spec. therefore youre going to make the rack longer if its positioned behind the centre point of the hub.... say you start off with half a turn on the O/S/F then switch and do half a turn on the N/S/F...........what happens if youre 1/2 a turn is actually nearer 3/4 cos you've got burst sausage fingers and have crap manual dexterity? yes, youll eventually bring it in to spec but surely it'll still be wrong as you wont have each side perfectly the same length  :-\ :-\ :-\

hope that makes sense lol
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 24 April 2013, 15:19:09
The issue with counting the turns is that it assumes that the replacement part has the same distance between the thread start and track rod end pin centre.......and there in lies the issue as many OEM parts don't.  :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 24 April 2013, 15:21:34
The issue with counting the turns is that it assumes that the replacement part has the same distance between the thread start and track rod end pin centre.......and there in lies the issue as many OEM parts don't.  :y

exactly. to me there sounds like too many variables. which is why surely I would think the only proper way to do it is with the lasers and setting each side up correctly that way. then its guaranteed to be spot on.

my teacher reckons that many service centres do alignments now. is that true?  I thought it was a pretty specialised area like WIM for example :-\
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 24 April 2013, 15:26:14
Geometry is more specialised and as we all know, there is more to it than having the kit!

You are setting but one of the three standard areas of adjustment.

As for accuracy and the comment re adjustement, this isnt an issue in reality as the image you see is reflected from the mirror via a datum and hene you actualy see an adjustment for each side.

Other key point is that the wheels should be on skid plates to get a proper measurement
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 24 April 2013, 16:18:00
cheers  Mark  :y :y :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 29 April 2013, 18:26:43
Afternoon guys,

AWESOME day today. Started off by removing struts....
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp3_zps34919217.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp3_zps34919217.jpg.html)
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp2_zpsb5aae857.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp2_zpsb5aae857.jpg.html)
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp4_zps3cb0a572.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp4_zps3cb0a572.jpg.html)
These are actually SUPER easy. Remove any brake lines, ABS lines etc that may be attached to the strut. Remove two securing bolts to the hub assembly and then undo the nuts or bolts in the strut tower...drop it down... DONE

Check tops and bottoms of coils for sheared parts, check the gaiters for cuts and check for fluid leaks. We didn't do spring removal as we don't have the proper equipment and in all honesty I really don't want to try it with the following kspring compressors which they do have. simple fact is theyre super dangerous and they scare the crap out of me....
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp5_zpsae8c918c.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp5_zpsae8c918c.jpg.html)

We did the first struts on a tigra and then the struts on this shite old N reg (I thik) Fiesta.....
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp1_zps4d68749b.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp1_zps4d68749b.jpg.html)
Little bit different..... remove one securing bolt to hub assembly and then get a big pry bar (I used a lady slipper :)) to get over the hub assembly and under the chassis...pry down and the strut will come up out of its mount. undo the strut tower nut. done.

WISHBONES AND LOWER CONTROL ARMS....

These attach to the subframe and I presume theyre there to stabalise everything  :-\ ill be honest we haven't looked at the theory yet so that's a guess. anyone want to chip in with what they do?  ;D

Anyhow this is a lower control arm.....
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp7_zps76b17c32.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp7_zps76b17c32.jpg.html)
...... and attaches to the hub assembly at the bottom via a ball joint.

This is a wish bone....
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp9_zps1b7028ed.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp9_zps1b7028ed.jpg.html)
.....and again attaches to the hub assembly via a ball joint.

both of triangular type shape for strength.

sadly my phone died during it and I wish i'd got pics cos it was super awesome.....

now I did the lower control arm on the vx tigra. it had definitely never been off  :o seriously, 5 minutes in and I took an executive decision..... everyone was struggling and we're supposed to use hand tools. i'm sorry but hand tools are sometimes redundant..... this was one of those moments!!! I went to the store and got myself an impact gun, an air line and a set of impact sockets. thing was off in 5 minutes  8) 8) 8) 8)

now I was half way through when my teacher came over and viewed what I was doing. he wasn't against me using the buzz gun but definitely took the view that I should try harder with the hand tools. hahahahahahaha b-ollox! i'm sorry but whats the point in me struggling for 3 hours with a breaker bar?  fek that.

I had a word with him afterwards and he reckoned that the buzz gun damages the threads of bolts removed ??? i'm sorry but what b-ollox. ive seen soooooo many suspension videos on line. and theyre used cos of the impacting motion breaking stuff loose. the alternative? struggle!

look forward to some comments especially regarding the buzz gun thang  :y :y :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 30 April 2013, 12:08:23
Must try harder.

The main damage risk with the 'gun' is fitting of items.

You should be able, with the correct breaker bar, to remove a fixing that a 'gun' wont touch!

So get practising (its argueable that your short cut is an opportunity missed  :y) as there will be fixings you wont be able to get the gun near which will be F-tight. Removing tight things with a breaker is a skill you need to learn as there is a certain amount of technique required.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 30 April 2013, 19:07:04
Fair enough comment mate... and luckily I had a few opportunities to use the breaker bar today  :y

on the subject of impact guns.... heres ours  8) 8) 8) 8) 8) 8) 8) 8) 8)
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp100_zpsefadbf6a.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp100_zpsefadbf6a.jpg.html)
I asked the technician if he knew what torque it would go to but he didn't know. i'm going to note the make and model to see if I can find out to compare to the electric ones i'm looking at :)
here's the shop air fixing....
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp101_zps8b407dff.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp101_zps8b407dff.jpg.html)
for some reason it shoots off the wall when I release it  :'( quite dangerous. anyone know what i'm doing wrong? others seem to just pop it off lol. and yes I am turning the air off before pulling it...... actually whilst typing..... I wonder if I should turn the air off at the line and then use buzz gun to use up all air between it and the wall thus leaving empty line and easy removal?  :-\

Anyway, today was rear dampers.

after knocking the main bolt loose with a breaker bar I used a ratchet to finish it off...
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp2222_zps358cfe48.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp2222_zps358cfe48.jpg.html)
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp1111_zps147a21cd.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp1111_zps147a21cd.jpg.html)

finally got the bugger out but had to drop the exhaust to get to one of the through bolts but was easy enough  :y note the transmission jack supporting the wheel in case the subframe dropped on removal. note also the very gay kid posing for the photo. why cant kids be normal?  ::)
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp1047_zps3e8456c4.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp1047_zps3e8456c4.jpg.html)

and the damper removed from the car....
(http://i1226.photobucket.com/albums/ee402/webbybear1/susp105_zpsedb27bef.jpg) (http://s1226.photobucket.com/user/webbybear1/media/susp105_zpsedb27bef.jpg.html)

ok, this should be an easy answer for someone................... why no spring? there was just this damper (or what i'd call a shock absorber)?
Title: Re: Mechanic School Blog
Post by: aaronjb on 30 April 2013, 19:17:21
French car, I'm guessing? They often use what's called "torsion bar" or "torsion beam" rear suspension where the spring action is provided when the rear trailing arm 'twists' a steel tube that always wants to return to rest.

Google can probably explain it better, my words are failing me (that may be because I'm on a conference call at the same time ;D))

BTW that windy gun looks like a fairly cheap example - it's identical to both my Sealey and the super-cheap Aldi/Lidl specials, so probably has a torque cap of <400lb/ft..
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 30 April 2013, 19:21:17
cheers Aaron. yeah French P.O.S! seen the spare wheel anchored underneath? LOL ::)

Ok thanks for that..... is that standard? or generally speaking do rears have shocks and springs like the miggy?

 :)
Title: Re: Mechanic School Blog
Post by: aaronjb on 01 May 2013, 10:16:30
I think predominantly cars now will have shocks & springs all round, either coil-over-shock (like the MR2) or separate (like the Omega) with either an arrangement of tie rods & trailing arms (Omega, MR2, etc) or occasionally double wishbones (300ZX, 350Z, etc)..

French stuff used to almost exclusively be torsion beam (my old Renault 19 16v was, as was the Renault 5 GT Turbo) which has the interesting side effect of massively promoting lift-off oversteer in corners which was either fun or buttock clenching depending on your point of view ;D

For some oddities try the original VW Beetle which had torsion beam suspension on the front and the rear, as does the Citroen 2CV - handling capabilities aside it's one of the most simple and robust suspension systems available, IMHO. Shocking handling, though (ever seen a 2CV go around a corner? It looks like it's going to fall over at any speed over walking pace!)..

BTW, when removing the airline you just need to keep a tight hold on the hose end as you click the release up with two fingers - unless they have a one-way valve in both fittings (fixed end and hose) they'll do exactly what you describe without a purge in the line somewhere (as you say, turning off the air and running the tool down would do it, but realistically I suspect most people just keep a firm grip ;))
Title: Re: Mechanic School Blog
Post by: YZ250 on 01 May 2013, 11:41:34
for some reason it shoots off the wall when I release it  :'( quite dangerous. anyone know what i'm doing wrong? others seem to just pop it off lol. and yes I am turning the air off before pulling it...... actually whilst typing..... I wonder if I should turn the air off at the line and then use buzz gun to use up all air between it and the wall thus leaving empty line and easy removal?  :-\

That's what we have to do at work with the air tools, otherwise the airline shoots out like a missile.  ;D ;D :y

Quite handy when the boss walks by.  ;)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 01 May 2013, 11:50:43
You can get valves which vent the line when turned off
Title: Re: Mechanic School Blog
Post by: aaronjb on 01 May 2013, 12:24:11
You can get valves which vent the line when turned off

That too (although I doubt Webby would be allowed to re-plumb his school or work ;)) - I have a very nice one at home waiting to go on that's pretty much identical to this one: http://store.norgren.com/uk/en/detail/airline-frl/combination-units-frl/range-is-bl64/bl64_401/combination-filter_regulators-and-lubricators-frl
Title: Re: Mechanic School Blog
Post by: biggriffin on 01 May 2013, 13:03:47
Best windy gun "in the world" in my opinion is a

Canadian pumatics or CP,  :)

Doah posted in wrong thread...
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 01 May 2013, 13:10:42
I rate the ingersol rand ones to
Title: Re: Mechanic School Blog
Post by: aaronjb on 01 May 2013, 13:34:41
I rate the ingersol rand ones to

Ditto - my budget IR one knocks spots off the Sealey one (and since I picked it up as NOS it was cheaper, too!)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 03 May 2013, 11:25:29
Hi guys,

I've got a big up date to do tonight on steering, toe alignment, camber alignment and castor angle. All interesting stuff :)

One thing i would like to know is this.....

following someones thread in the gen. help and my subsequent learning of the ABS system i believe it goes like this:

ABS sensor gives signals to the ABS ECU (a computer solely for the use of the ABS system). if at any point the ABS ECU detects that one or more wheels is giong to lock up it sends a signal to the hydraulic modulator. this modulator then reduces hydraulic pressure going to that/those wheels thus reducing braking force thus stopping/limiting lock up.

have i got that right?

if so, i have 2 questions.....

1.) where on the mig is the hydraulic modulator and ABS ECU located?
2.) how come the ABS has its own ECU and is not part of the main ECU?

:)
Title: Re: Mechanic School Blog
Post by: albitz on 03 May 2013, 11:47:32
1. ABS pump/module ecu is on pass side inner wing underneath PAS reservoir.
2. ECU is an electronic control unit. Each particular system on the car has its own control unit (engine/transmission/braking/airbags etc.) although some of them are linked to each other and can communicate with one another to some degree.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 03 May 2013, 11:58:40
That makes perfect sense. thanks albus ;)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 03 May 2013, 13:25:55
The ABS ecu monitors each wheel using a sensor (most offen a reluctance type sensor which senses the rotation of a toothed ring).

It looks at the speed difference between wheels and if one is seen to suddenly slow under braking the it release the hydraulic brake pressure to that corner and then re-applies it (many times a second).

These days they also offer additional functions which include traction control (on detecting wheel spin a signal is sent to the engine ECU to back off power) and stability programs (be it very simple as per facelift Omegas or more complex when a yaw sensor is installed).

All pretty straight forward.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 04 May 2013, 20:02:04
Hi guys,

Am planning to do the update I promised later tonight re the suspension stuff :)

For now though I thought i'd update on something I have found really amusing and those little quirky things the wife does  ::) ;D

Anyway, as I've mentioned before i'm a huge fan of Eric the Car Guy (ETCG) on youtube and i'm always watching his vids. Anyway I was watching this particular one where a fan sends in Eric some new headlights for his Subaru.....

http://www.youtube.com/watch?v=WX026M1DdrE

they arrive and are the correct size and everything but the connectors are different so he has to make some modifications by cutting the old connectors off and attaching them to the new connectors by soldering them in.

Anyways, wanting to learn how to do this and thinking this would be a great skill to have for the electric side of mechanics I said to the mrs ''have you ever soldered''....she was like ''yeah, of course I have...my kit is in the basement''.  ??? ??? ??? ??? ???

top tray full of pins... presumably used for back probing  :-\
(http://i1226.photobucket.com/albums/ee402/webbybear1/soldering3_zpsfeb61c2e.jpg) (http://s1226.photobucket.com/user/webbybear1/media/soldering3_zpsfeb61c2e.jpg.html)

the soldering gun and stand...
(http://i1226.photobucket.com/albums/ee402/webbybear1/soldering2_zpsb7c33a60.jpg) (http://s1226.photobucket.com/user/webbybear1/media/soldering2_zpsb7c33a60.jpg.html)

and this really awesome old skool multimeter...still works perfectly  :y
(http://i1226.photobucket.com/albums/ee402/webbybear1/soldering_zpsa5c2489e.jpg) (http://s1226.photobucket.com/user/webbybear1/media/soldering_zpsa5c2489e.jpg.html)

Well life is full of surprises... and ive booked a training session in for tomorrow  ::) ;D ;D ;D
Title: Re: Mechanic School Blog
Post by: Shackeng on 04 May 2013, 20:12:36
I thought you were going to say she misheard you for 'Soldiered', and you were going to find all her army kit! Good find, why hasn't mine got skills like that. ??? Oh, she cooks and gardens, that'll do, :y :y :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 04 May 2013, 20:18:40
I thought you were going to say she misheard you for 'Soldiered', and you were going to find all her army kit! Good find, why hasn't mine got skills like that. ??? Oh, she cooks and gardens, that'll do, :y :y :y

 ;D ;D ;D

she fixed the table saw I broke a few weeks back also  :-[ :-[ :-[ :-[ :-[
Title: Re: Mechanic School Blog
Post by: Shackeng on 05 May 2013, 10:07:05
No wonder you're doing the mech course, you need to have some skills they haven't! 8) :y :y :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 05 May 2013, 12:29:15
No wonder you're doing the mech course, you need to have some skills they haven't! 8) :y :y :y

Exactly mate  ;D :y :y :y
Title: Re: Mechanic School Blog
Post by: Taxi_Driver on 05 May 2013, 19:18:51
No wonder you're doing the mech course, you need to have some skills they haven't! 8) :y :y :y

Exactly mate  ;D :y :y :y

Ever thought of getting one up on her and learning needlecraft  ::) ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 06 May 2013, 17:36:04
No wonder you're doing the mech course, you need to have some skills they haven't! 8) :y :y :y

Exactly mate  ;D :y :y :y

Ever thought of getting one up on her and learning needlecraft  ::) ;D

lol cant mate... she sews and knits too  :-[ :-[ ::) ;D

ps, back on topic slightly, I haven't updated on suspension stuff as my notes are round my mums and I forgot them  ::) ill have rthem tomorrow so should update then :)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 08 May 2013, 18:10:57
Afternoon guys, how are ya? :):)

Well I haven't had my lesson in soldering yet!  >:( >:( >:( >:( >:( not the wife's fault.... I been ill most of this week... never suffer from migraines and get two in two days  :'( :'( :'( :'( didn't really take anything in during practical other than we did chassis checks.. I think  :-\ lol

Anyway I was fine today for theory and got back on the learning curve  8)

So.... steering....I've touched on it before re the rack and pinion stuff but I want to talk about the stuff I learned in theory.

Ackerman principle: ''if the track rod is the same length as the distance between pivot points the inner wheel, when turning, will not turn at a bigger angle. if however the track rod is shorter than the pivot point distance (assuming the track rod is placed behind the wheels) then the inner wheel, when turning will turn at a greater angle which is desired when turning a corner''.

I still don't get how? can someone explain how it will do this?

steering boxes......I know that the omega utilises the box but Im not sure I get how these work.

this is a pic from the bears colouring book.....

(http://i1226.photobucket.com/albums/ee402/webbybear1/steeringbox_zps0d8b02d7.jpg) (http://s1226.photobucket.com/user/webbybear1/media/steeringbox_zps0d8b02d7.jpg.html)

now I can see of course the steering shaft turning and the effect of that on the cam roller.... but then I just cant see how it transfers that twisting motion to the lateral steering  :-\

also is the track rod in place of the rack so in essence it is what moves the wheels left/right?



Title: Re: Mechanic School Blog
Post by: Andy B on 08 May 2013, 18:17:46
....
now I can see of course the steering shaft turning and the effect of that on the cam roller.... but then I just cant see how it transfers that twisting motion to the lateral steering  :-\

The twisting motion moves the steering arm (the steering idler arm is opposite it)



also is the track rod in place of the rack so in essence it is what moves the wheels left/right?


A rack system still has track rods, they're just fastened to arms that are connected to either end of the rack.
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 08 May 2013, 18:22:38
Thanks Andy. So can I just clear something up cos everyone uses different names for stuff  ;D.........

is what ive called the ''drag link'' the steering idler?
Title: Re: Mechanic School Blog
Post by: Andy B on 08 May 2013, 18:36:36
Thanks Andy. So can I just clear something up cos everyone uses different names for stuff  ;D.........

is what ive called the ''drag link'' the steering idler?

I'm not that well up on the terms myself  :-\ but I think the drag link is the bar that connects the arm from the steering box to the idler arm  :-\
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 08 May 2013, 18:45:27
Having looked at it again I've probably been unclear on what i'm confused about...

I get that the steering wheel turns and the box turns this motion in to backwards and forwards motion.... this will then ''pull'' the arm forward therefore turning left and then it'll push it backwards therefore turning right.

I just don't get how that steering turning motion is physically turned in to that lateral motion.  the little bubble on the right highlighting the roller just doesn't make sense to me  ::)
Title: Re: Mechanic School Blog
Post by: Nick W on 08 May 2013, 22:16:19
You might find it easier if you find a diagram of how the Omega steering linkage works.
Then you can apply the knowledge to the solid axle in your diagram. Although you're unlikely to see one on a car unless you start working on '30s cars, or modern trucks.
And after that, you could look up a 'cross steer' solid axle, which is different again!

At least a rack is easy to figure out.
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 09 May 2013, 13:13:46
Thanks Andy. So can I just clear something up cos everyone uses different names for stuff  ;D.........

is what ive called the ''drag link'' the steering idler?

I'm not that well up on the terms myself  :-\ but I think the drag link is the bar that connects the arm from the steering box to the idler arm  :-\

Yes, in the case of the Omega where effectively the drag link and track rod are a combined assembly

If you consider a Land Rover, its the arm from the steering box to the near side track arm (which is part of the hub)
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 09 May 2013, 13:20:01
Having looked at it again I've probably been unclear on what i'm confused about...

I get that the steering wheel turns and the box turns this motion in to backwards and forwards motion.... this will then ''pull'' the arm forward therefore turning left and then it'll push it backwards therefore turning right.

I just don't get how that steering turning motion is physically turned in to that lateral motion.  the little bubble on the right highlighting the roller just doesn't make sense to me  ::)

have a look at a diagram for a recirculating ball steering box (as per the Omega).

Have a little look at this its as simple as it gets (much more complex with power assist etc!)

http://www.howstuffworks.com/steering3.htm
Title: Re: Mechanic School Blog
Post by: Entwood on 09 May 2013, 13:25:38
Another good write up here ...

http://www.carbibles.com/steering_bible.html
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 09 May 2013, 19:20:38
MDTM/Entwood, thanks for those posts; I looked for the ehow and how stuff works but couldn't find it  :-[

Anyways I've found this pic of the underbody front of the omega (2.0L so I am assuming its the same steering system)

(http://i1226.photobucket.com/albums/ee402/webbybear1/undercar_zpsbbda594c.jpg) (http://s1226.photobucket.com/user/webbybear1/media/undercar_zpsbbda594c.jpg.html)

so. no. 8 is the track rod, no. 7 is the steering idler/drop arm that transfers the movement from the steering box to the track rod and I presume the steering box (i.e, the gearing attached to the steering shaft) is just above no. 7?

 :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 09 May 2013, 19:26:54
...oh and where would the pitman arms be in this pic of the omega..... or doesn't it have them?  :)
Title: Re: Mechanic School Blog
Post by: TheBoy on 09 May 2013, 19:32:02
8 is centre tie rod

6 and 10 are track rods

9 is steering box and pitman arm

7 is steering idler
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 09 May 2013, 19:40:23
Thanks TB,

Shouldn't the steering box be up above the steering idler though as that's below the drivers position, therefore the steering shaft would come down from there?  :-\

 :y
Title: Re: Mechanic School Blog
Post by: TheBoy on 09 May 2013, 20:11:42
sorry, yes, for rhd swap 7 and 9  :-[
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 09 May 2013, 20:22:38
cheers mate, I think it makes sense now.

I presume when replacing idler, box gears etc they'd be quite a straight forward job? ive checked out the guide. looks quite easy  :-\
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 13 May 2013, 21:53:40
Evening guys, how are we???

Well we've had our suspension systems theory and if i'm honest its quite involved and as I want to update on alternator and starter practical tonight I thought id go through the suspension systems for front and then rear.

FRONT SUSPENSION SYSTEMS:

MacPherson Strut:
damper housed in spring coil. at the top it attaches to the strut towers in the engine bay. at the bottom it connects to the hub assembly:
(http://i1226.photobucket.com/albums/ee402/webbybear1/suspi1_zps939f297b.jpg) (http://s1226.photobucket.com/user/webbybear1/media/suspi1_zps939f297b.jpg.html)
I believe this is the most common type of front suspension on modern cars.

Double Wishbone:
wishbone attached at the top of the hub assembly. a wishbone attached to the bottom of the hub assembly. spring and damper lives between the two. fully independent i.e. moves independently of the other strut on the other side.

Double Link and Radius Arm.
I don't know much about this; all I got is one picture in my assignment  :-[ simply looks like two rods attaching to the hub assembly  :-\ :-\ :-\ anyone confirm that?

REAR SUSPENSION:

Rigid beam axle:
coil springs housing dampers so struts affectively. big hunk of metal connecting the rear hub assemblies ( I think Richard Hammond once described this set up on a 2005 mustang as ''a whacking great gurder with two wheels on the end). non-independent

coil spring and semi trailing arm:
this is fully independent with springs and dampers. there appears to be like two triangular plates that attaches to a subframe allowing everything to pivot and flex. drive shafts coming out of the diff not attached in any way to the suspension. this, I believe is what the omega utilises.

finally the coil spring and leading arm:
separate springs and dampers attached to the car via a beam attached to the diff. 4 metal rods attaching to the car. again don't really have much info on this.

Where does the torsion bar come in to this? obviously all the ones ive highlighted have springs and dampers. are these ever utuilised in addition to springs? I assume not. is the torsion bar an old system?


ok so now some photos  :) :) :) :) :) :) :)
when removing an alternator the order goes like this:
...disconnect battery
...disconnect electrical connections to alternator
...remove drive belt
...remove alternator

(http://i1226.photobucket.com/albums/ee402/webbybear1/alter9_zps3b390209.jpg) (http://s1226.photobucket.com/user/webbybear1/media/alter9_zps3b390209.jpg.html)

the following is a pic of us testing the alternator whilst off the car....the alternator takes a live from the battery and earths (grounds  :-\ :-X :D) due to its connection to the block. it then has another live lead coming OUT of the alternator which distributes the electricity it produces.
to test whilst off the car...... hook a battery up to the live connection and earth where it would connect to the block. then hook up a circuit to the distribution line with a bulb in it. use a buzz gun to spin the alternator and watch the bulb light up  :) :) :)
testing it on the car would just be a dynamic test... hook your DVOM up to the car whilst its idling. presumably leave for a few minutes and ensure it doesn't drop below 13.8-14.5v.
(http://i1226.photobucket.com/albums/ee402/webbybear1/alter3_zps816540c9.jpg) (http://s1226.photobucket.com/user/webbybear1/media/alter3_zps816540c9.jpg.html)
(http://i1226.photobucket.com/albums/ee402/webbybear1/alter2_zps8ce103ec.jpg) (http://s1226.photobucket.com/user/webbybear1/media/alter2_zps8ce103ec.jpg.html)

the following is a shot of the tensioner system that's part of the alternator. you loosely fit the alternator in [place and loosely fit the belt, then the bracket in the middle of the pic... you screw the bolt in and as the bolt tightens it pushes against the bracket which in turn forces the alternator outwards and tightens the belt :)
(http://i1226.photobucket.com/albums/ee402/webbybear1/alter7_zpsb4944af2.jpg) (http://s1226.photobucket.com/user/webbybear1/media/alter7_zpsb4944af2.jpg.html)

STARTERS:

In short when the ignition key is turned it completes the circuit to the starter. the solenoid creates magnetism and that in turns spins the mechanical motor. this is splined to the flywheel and turns it to start the combustion process (which then ''takes over'').

in this shot you can see the cog that turns the flywheel.
(http://i1226.photobucket.com/albums/ee402/webbybear1/alter6_zps95978706.jpg) (http://s1226.photobucket.com/user/webbybear1/media/alter6_zps95978706.jpg.html)

the hole where the starter lives. I tried to take this shot so you could see the flywheel inside... not oo sure if you can see it tho  :-\
(http://i1226.photobucket.com/albums/ee402/webbybear1/alter1_zps4e8ce7fe.jpg) (http://s1226.photobucket.com/user/webbybear1/media/alter1_zps4e8ce7fe.jpg.html)
(http://i1226.photobucket.com/albums/ee402/webbybear1/alter5_zps21a16c4b.jpg) (http://s1226.photobucket.com/user/webbybear1/media/alter5_zps21a16c4b.jpg.html)

testing a starter off the car... hook up a battery positive to the part that normally receives the live. and a batt. negative to where it normally touches the block. then hook up a wire/alligator clip to the electrical connector. and touch the live with the other end. motor will engage and spin.
(http://i1226.photobucket.com/albums/ee402/webbybear1/alter4_zps46440c40.jpg) (http://s1226.photobucket.com/user/webbybear1/media/alter4_zps46440c40.jpg.html)

was a really good day. hope you enjoy the update and as ever comments & constructive criticism always welcome  :y :y :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 14 May 2013, 20:12:21
Word up. My dogs :)

Awesome day at school today. You may have seen my post regarding my indicators not flashing. Well I located the flasher relay, it wasn't clicking when indicators were activated so I replaced it and they work. Took both relays in to school today to test them. Quite interesting as this is a 3-pin relay. This is the relay (not the actual one but similar):

(http://i1226.photobucket.com/albums/ee402/webbybear1/flasherrelay_zps860cec12.png) (http://s1226.photobucket.com/user/webbybear1/media/flasherrelay_zps860cec12.png.html)

me and the teacher looked at the wiring diagram and worked out that pins 31 and 49 (iirc) were the trigger circuit.... 49a was the high amp circuit. we hooked it up to a battery and it was dead! good one worked great :)

Anyway as I've maintained my lead on the other kids in terms of work done we got to do some electrical diagnosis on lighting systems. really good fun and I'm really loving the electrical diagnosis part.

anyway this brings me back on to electrical diagnosis  ::) I now think i'm in a position to explain myself a bit more and i'm going to (3rd time lucky) explain what I would do in the case of some FACTORY FITTED parking semsors (generic, not omega).

so I pull the wiring diagram for the parking sensors and I find this..... (ive drawn trhis myself... a simplistic look at a saab diagram):
(http://i1226.photobucket.com/albums/ee402/webbybear1/RearParkingSensorWiringDiagram_zpsf4919eb8.png) (http://s1226.photobucket.com/user/webbybear1/media/RearParkingSensorWiringDiagram_zpsf4919eb8.png.html)

so this is what I would do :)

So, from a diagnostic point of view we would check the simplest thing first: debris on the outside of the sensors as this can affect it's performance. 
 
Fuse next as it's the next easiest to check and is located (from what I could gather rom the Saab forum) in the fusebox in the front passenger compartment. While there we can check the fusebox connection where the fuse plugs in to.
 
If that's good then we would go to the sensors themselves; disconnect and do a resistance check. Also check for any visual signs of a bad sensor.
 
If they're good then we can check for voltage coming to the sensor by activating the sensors, connecting our DVOM to the connector. Then connect the other lead on our DVOM to a known good ground. If no voltage there is a short somewhere which we can trace back.
 
If voltage present then we could go for the beeper, then the control module. I assume the beeper would also be a resistance check and possibly hooking up to a battery off the car to see if it beeps? And then finally replacing the module if everything else tests good?

now I know that wiring diagrams don't provide diagnostic detail but they do include every component youd need to check in order to diagnose a fault.

comments welcome  :y
Title: Re: Mechanic School Blog
Post by: Entwood on 14 May 2013, 20:21:02
The Omega system as fitted by VX has its own built in test system, when powered and good it will make a single beep on selecting reverse, if any sensor is faulty it will emit a continuous beep.

Makes diagnosis easy ... if there is no beep on selecting reverse either a) speaker dead/disconnected  b) no electrics to ECU (fuse/wiring ??) c) ecu FUBAR

If the continuous beep occurs there is a test plug that can be removed, then by counting the beeps that occur it will tell you which sensor(s) is (are) at fault.

:)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 14 May 2013, 20:26:16
Cheers Entwood.... that's pretty easy then and definitely a score for GM. And makes sense why you advised me last time to research the exact system you're looking at before going straight to a wiring diagram.

If however, like in the Saab example above that there's no easy diagnosis with the test plug and all you have is the wiring diagram.... would my way be best?

 :)
Title: Re: Mechanic School Blog
Post by: Entwood on 14 May 2013, 20:37:09
Cheers Entwood.... that's pretty easy then and definitely a score for GM. And makes sense why you advised me last time to research the exact system you're looking at before going straight to a wiring diagram.

If however, like in the Saab example above that there's no easy diagnosis with the test plug and all you have is the wiring diagram.... would my way be best?

 :)

Personally I'd attack things a tad more logically.

If you use your diagram .. the speaker is an independent "branch" so I would check the speaker first, is there a speaker output voltage from the ECU ... if there IS then the system is working you just can't hear anything .. suspect speaker ..

If there is no speaker voltage then the problem is somewhere  along the "main line" ... so start at the fuse, then the wiring to the ECU, is power reaching the ECU (input voltage) ? If it isn't .. reverse selector? wiring ??  If it is .. is power LEAVING the ECU .. check for output voltages ?  If in but not out .. suspect ECU.  If output OK is the power reaching the sensors ... and so on ...

Basically, start at one end and work along in a continuous manner .. your way you are jumping about all over the place ....  but that's just the way I was taught to fault trace .. :(
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 14 May 2013, 20:42:53
that's exactly what I was looking for  :y the reason I am jumping around in my approach is just i'm trying to go on easiest access first  :)

I've never actually seen an ECU other than it being a square box in the engine bay with a HUGE wiring harness/connector going in. can you take the lid off and find the connectors to search for the voltage coming from there?  :)
Title: Re: Mechanic School Blog
Post by: Entwood on 14 May 2013, 23:35:43
that's exactly what I was looking for  :y the reason I am jumping around in my approach is just i'm trying to go on easiest access first  :)

I've never actually seen an ECU other than it being a square box in the engine bay with a HUGE wiring harness/connector going in. can you take the lid off and find the connectors to search for the voltage coming from there?  :)

ECU will have a loom going in .. your tester can be used with needle point feelers to check for voltages through the wires, you just need to be sure which ones you are checking !! So colour codes off a wiring diagram or good research and wire following - the latter being very time consuming !!
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 15 May 2013, 12:21:02
Just a note regarding the starter and alternator tests, the on car tests are actualy more valid as the bench tests have no significant loads (be it engine compression for a starter or electrical loads for the alternator) and its under such conditions that the faults will be visable.

As an overview of an alternator and how it works, consider the following.

A basic alternator (e.g. not a modern ECU controlled unit) consists of a stationary part (stator) and a rotating part (rotor), rectifier, regulator and as the name suggests, it produces an alternating current (AC) and not a direct current (DC).

This current is produced by exiting a coil on the rotor to produce a magnetic field, as this magnetic field rotates, it induces a current in a set of windings in the stator.

The stator will have at least three windings (usualy many more!) and produces three phase AC.

To turn this AC into DC to charge a battery it is fed into a rectifier (often refered to as a bridge rectifier or bridge), this is made up of 6 diodes which rectify the AC into DC.

So, thats the basics, there are a few more bits to consider.

Voltage regulation, if not controlled the output voltage will increase to high levels as the rotor speed goes up and/or the electrical load reduces, to combat this, a regulator is fitted.

This device controls the amount of current that is fed to the rotor winding via the slip rings and brushes and hence it is possible to vary the magnetic field in the rotor. This consequently varies the stator currrent and therefore the output voltage. The regulator measures the output voltage and automaticaly limits it to a preset value (this can be upto 14.6V for a calcium battery based system and can be seen with little electrical load and a charged battery).

The dash lamp does have a main use to. The basic alternator regulators do NOT take the power for the field from the battery (or they the rotor filed would be permanently energised with the igniton off and drain the battery), they get it from the dash lamp and an additional small rectifier.

So when you start the car, the ignition provides battery positive to one side of the lamp, the other side is connected to the regulator, this gives the regulator a feed to initilaise the field winding on the rotor (this explains why the bulbs used for the charge indicator are normaly quite a few watts). As the rotor starts to spin, the stator windings produce an output current, this is rectified by the additional small rectifier which feeds the resulting volts to the regulator on the lamp side. The bulb now goes out as it has positive volts on both sides and the regulator now has an alterntive power source from the alternator

So possible issues.

Regulator failure - These normaly fail short circuit and hence the output volts go way beyond the max volts as there is no control present, note the dash lamp will extinguish in this case. If they go open circuit then dash lamp will remain on.

Rectifier failure - Normaly spotted by reports of poor charging and a slightly flickering dash lamp. This is because only one of the diodes generaly fails at a time so the alternator still outputs current but it is reduced.

Dash bulb failure - will stop the alternator working altogether.

Bearing failure - Results in noise

Brush wear - Very rare these days although the awful old top mounted brush system as used by lucas in the 70's/80's does suffer this. Symptoms would be no charging and dashlight iluminated.


As an aside, those who have ever stripped an alternator may have noticed that the iron sections of the rotor are triangular in shape, this is by design and is done so that the AC output is not a true sinusoid and is more 'flat topped' with steeper edges. This gives the result of an electricaly quieter alternator with less 'ripple' on the output.

Dont be afraid of alternators, they are simple and pretty easy to repair.
Title: Re: Mechanic School Blog
Post by: aaronjb on 15 May 2013, 13:12:00
Where does the torsion bar come in to this? obviously all the ones ive highlighted have springs and dampers. are these ever utuilised in addition to springs? I assume not. is the torsion bar an old system?

Torsion beam (since I brought it up, I suppose I ought to answer this ;)) is - on the rear - usually a semi trailing arm suspension where you have to imagine that the spring is attached to the pivot point of the trailing arm..

Harder to describe than it really is if you look at one :y

A good example (well, easy to see!) is on the 2CV where both front and rear is torsion beam; on the front it's a 'leading arm' and on the rear a 'trailing arm' but you get the idea:

(http://www.2cvcity.com/wp-content/uploads/2010/02/107-0712_IMG.jpg)

The round tube going across the chassis is the torsion beam element while the black curved arm(s) toward the bottom of the picture are the trailing arm(s) with the wheel attached. On other cars the damper (shock absorber) would go between the wheel end of the trailing arm and the chassis, but the 2CV uses a bell crank (i.e. a protrusion on the trailing arm that, in this case, would be pointing toward the ground) with the damper connected between that and the chassis in a horizontal plane - you can see it in the photo, just.


Here's a double wishbone torsion bar setup where the red part is the torsion bar, twisted as the lower wishbone assembly rotates, to provide the 'spring' effect:

(http://www.carbibles.com/images/longitudinal-torsion-bar.jpg)


All in all they're largely rare on modern cars so not worth losing too much sleep over as long as you know the basics and when to spot one (usually there's no 'spring' visible which is a bit of a giveaway!).. All round torsion cars would be things like the 2CV and original Beetle with most French small cars of the 1980s and 1990s having rear torsion beam only with front Mac struts.


Title: Re: Mechanic School Blog
Post by: omega3000 on 15 May 2013, 20:14:42
Quote
All round torsion cars would be things like the 2CV 

Great for off roading ...
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 16 May 2013, 09:24:06
.. and then you get exotica like my old morris ital that featured torsion bars and lever arm shock absorbers on the front and leaf springs on the back to truly give you the worst of both worlds when it comes to comfort and handling. <shudder>
Title: Re: Mechanic School Blog
Post by: aaronjb on 16 May 2013, 12:28:55
Actually thinking more about it, is the 2CV actually torsion beam? I always thought it was, but those big central canisters also contain springs.. so is it just crank arm remote springs and shocks?

The Beetle is definitely torsion beam front & rear though, isn't it..
Title: Re: Mechanic School Blog
Post by: Shackeng on 16 May 2013, 12:48:39
Actually thinking more about it, is the 2CV actually torsion beam? I always thought it was, but those big central canisters also contain springs.. so is it just crank arm remote springs and shocks?

The Beetle is definitely torsion beam front & rear though, isn't it..

The early ones had torsion bar front, and independent rear, suspension, later models had Macpherson struts on the front. I had Beetles as second cars for about 20 years, and drove in RAC controlled rallies in a '59 Beetle, (semaphore arm indicators) even winning a special stage once! Although the 6V electrics did not make for good headlight beams.  :y
Title: Re: Mechanic School Blog
Post by: Kevin Wood on 16 May 2013, 14:21:10
Actually thinking more about it, is the 2CV actually torsion beam? I always thought it was, but those big central canisters also contain springs.. so is it just crank arm remote springs and shocks?

Yes, I was wondering about that.

Never got close enough to a beetle to know what they have, but did get tempted to build one of these once:

http://www.madabout-kitcars.com/kitcar/kitcar_details.php?7 (http://www.madabout-kitcars.com/kitcar/kitcar_details.php?7)

Looks fun, in a minimalist, "drive it at 10 tenths all the time" kind of way. ;D
Title: Re: Mechanic School Blog
Post by: aaronjb on 16 May 2013, 15:03:30
Thanks Shackeng - I wonder what car I was thinking of that's all torsion beam.. either that or I've just been very misled about the 2CV for years :)


Kev, you've started something now.. Amy has a thing for 2CVs and I just mistakenly suggested we could turn one into one of those (although now I check they no longer make that kit, but they do make a bike or VW-powered 'Zero') to which her response was "Oh yes!".

Looks like I may have picked up another project ;D
Title: Re: Mechanic School Blog
Post by: Shackeng on 16 May 2013, 20:56:49
Thanks Shackeng - I wonder what car I was thinking of that's all torsion beam.. either that or I've just been very misled about the 2CV for years :)

Kev, you've started something now.. Amy has a thing for 2CVs and I just mistakenly suggested we could turn one into one of those (although now I check they no longer make that kit, but they do make a bike or VW-powered 'Zero') to which her response was "Oh yes!".

Looks like I may have picked up another project ;D

I had a Renault 16TL which also had torsion bar rear suspension. I found it very good on it and the Beetle, giving no problems whatsoever and good road holding, (OK, the Beetle could turn over if pushed ::)). I was surprised when VW went with the Mac struts, perhaps to give more space between the wheels for the tank, or luggage. No doubt someone on here will know. :y
Title: Re: Mechanic School Blog
Post by: Marks DTM Calib on 17 May 2013, 08:37:56
Be careful as the torsion beam/tube/bar setup is still very widely used.

The setup where the spring function is part of the beam/tube/bar is pretty much extinct as it has a major number of compromises with repsect to road holding, noise and handling characteristics. It also used to see weld failures and placed megs stresses on certain parts (e.g. the Renaults used to eat the rubber bushes at the end of the torsion bars)

Plenty of setups still about with beam/tube/bar setup and seperate coil springs.
Title: Re: Mechanic School Blog
Post by: Shackeng on 17 May 2013, 09:04:09
Be careful as the torsion beam/tube/bar setup is still very widely used.

The setup where the spring function is part of the beam/tube/bar is pretty much extinct as it has a major number of compromises with repsect to road holding, noise and handling characteristics. It also used to see weld failures and placed megs stresses on certain parts (e.g. the Renaults used to eat the rubber bushes at the end of the torsion bars)

Plenty of setups still about with beam/tube/bar setup and seperate coil springs.

I had my R16 for 10 years, and 85k with no issues, but I am not a hard driver. The body rusted off the 'chassis' before mechanicals failed, so no surprise that you never see one now, but I loved that car, it was the only one I've owned that approached the Omega for comfort, (inc XJ6). :y
Title: Re: Mechanic School Blog
Post by: Shackeng on 17 May 2013, 09:10:11
Actually thinking more about it, is the 2CV actually torsion beam? I always thought it was, but those big central canisters also contain springs.. so is it just crank arm remote springs and shocks?

Yes, I was wondering about that.

Never got close enough to a beetle to know what they have, but did get tempted to build one of these once:

http://www.madabout-kitcars.com/kitcar/kitcar_details.php?7 (http://www.madabout-kitcars.com/kitcar/kitcar_details.php?7)

Looks fun, in a minimalist, "drive it at 10 tenths all the time" kind of way. ;D

With apologies to Webby for being off topic, I certainly drove my first beetle with the 'heel to the steel', the engine was unburstable, if low on power, but great fun to drive, and an ideal car for first owners, as the engine could be dropped out in comfortably less than 1 hour. My son started out with one and loved it also :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 10 June 2013, 21:41:56
Evening guys.

Apologies for the delay of a couple of weeks but in all honesty I have just 4 days left!!!!  :'( its gone so darn quickly.

I've got a transmission update to do but that's pretty much it.

I had a servicing practical assessment today. Went really well and should pass that with ease but there were a few things that proved how much of a rookie I still am. however i'm not phased by this. I feel I've probably learned about 2%. I have a basic understanding of everything. I can do most jobs now and more impoirtantly understand why i'm doing them. but as said im still nowhere near being the finished article.

one example today.... we had to get rear drums off to measure the drum and the shoes. no problem at all. but re-adjusting the shoes after I had to have help with as i'd never seen the set up before... it was a 95 ford fiesta and instead of having like an adjusting wheel that you clicked round it had this little obscure notch that I had to twist upwards whilst pushing the shoes outwards.. they then clicked and I could set the drum up properly.

thers still plenty I don't know but I do appreciate all of your help over the past year MASSIVELY. its been great to talk about my day in the calm out of the shop, understand things and have your take on everything.

as said I still want to update my transmission stuff so look out for that but ill prob get my exams done this week then do that  :y :y :y
Title: Re: Mechanic School Blog
Post by: PhilRich on 10 June 2013, 21:49:15
Whatever you do webby, DO NOT even THINK about a little tree shaped item that hangs from your windscreen and causes MOT failure! Oh, and make a note of your postcount ;D
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 14 August 2013, 13:23:16
Well guys, got through the post this yesterday  :) :) :) :)

(http://i1226.photobucket.com/albums/ee402/webbybear1/campg_zpse2c8bbf5.jpg) (http://s1226.photobucket.com/user/webbybear1/media/campg_zpse2c8bbf5.jpg.html)

So. in the process of having my student loan approved. then will be back in September with a new thread... ''mech. school blog - level 3'' lol
Title: Re: Mechanic School Blog
Post by: Andy B on 14 August 2013, 13:57:34
Well done Stephen Webby!  :y  :y  :y
Title: Re: Mechanic School Blog
Post by: symes on 14 August 2013, 13:59:05
congratulations mate :y :y :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 14 August 2013, 16:28:33
lol cheers lads. quite chuffed actually.

so looking in to the course list for the level 3 we'll cover everything we did this year but of course in a lot more detail. however the following areas will be included:

timing belts (did a couple on stands but not much)
pas racks
clutch replacement
gearbox replacement

and

this is the best bit.......

welding!!! :):):):)

as said though ill start a brand new thread for level 3 so watch this space. am going to get a better phone too so i can take some quality photos
Title: Re: Mechanic School Blog
Post by: TheBoy on 14 August 2013, 17:46:52
Well done Webby :)
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 14 August 2013, 18:26:31
cheers mate  :y
Title: Re: Mechanic School Blog
Post by: dbdb on 17 August 2013, 01:44:38
Well done :).  Welding is great fun to learn, try to start on gas, move to arc and then MIG which is most difficult to easiest.  MIG then appears as a joy to use, just like a giant glue gun. My first MIG welding project was a custom set of car ramps wide and low enough to get my first omega up on without scraping the bodywork. Always trusted them, still use them.

Plasma cutting is quite rewarding too, better than gas cutting.
Title: Re: Mechanic School Blog
Post by: dbug on 17 August 2013, 01:57:51
Well done Webs  :y
Title: Re: Mechanic School Blog
Post by: dad1uk on 17 August 2013, 22:25:24
Well done Webby, and thanks for the informative posts :y - must admit I haven't read all of it though ;D ;D
Title: Re: Mechanic School Blog
Post by: albitz on 17 August 2013, 23:07:01
Well done Webstar. :y
Title: Re: Mechanic School Blog
Post by: omega3000 on 18 August 2013, 12:02:20
Well done mate  8) 8) , welding was my next on the list of things to learn but hey ho  :'(
Title: Re: Mechanic School Blog
Post by: Shackeng on 19 August 2013, 22:13:39
Congratulations Webby, good luck with the next bit. :y :y :y
Title: Re: Mechanic School Blog
Post by: Webby the Bear on 20 August 2013, 07:10:56
thanks all fo the comments. it is so enjoyable. there wasn't one day I didn't want to be there. looking firward to being out of my comfort zone and moving away from servicing too  :y
Title: Re: Mechanic School Blog
Post by: jonnycool on 31 August 2013, 09:07:54
Thanks for this blog Webby, it's been interesting reading  :y

And well done  :)