Omega Owners Forum
Chat Area => General Car Chat => Topic started by: Webby the Bear on 18 November 2013, 19:58:02
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As above. I had theory on Thursday and this came up. It looks like a tape measure and i quote ''is a precision clearance gauge for the measurement of clearance between fitted surfaces''.
cant see why youd need it if youve got a micrometer and feeler blades,
am i missing something? :-\
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As above. I had theory on Thursday and this came up. It looks like a tape measure and i quote ''is a precision clearance gauge for the measurement of clearance between fitted surfaces''.
cant see why youd need it if youve got a micrometer and feeler blades,
am i missing something? :-\
micrometer and feeler gauges are metal, and if used incorrectly can actually damage the surfaces that they are measuring the gap between
You also need full access to both surfaces so you can insert the micrometer "feelers" or the feeler gauge "tongue" ... plastigauges get around this access problem, especially when trying to measure bearing surface clearances, when access would be extremely difficult.
Imagine trying to get feeler gauges/micrometer to measure the clearance in a split bearing !! With plastigauges you can fully assemble, then disassemble and by reading the plastigauge you KNOW what the clearance was /will be when re-assembled .. even inside a closed surface.
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As above. I had theory on Thursday and this came up. It looks like a tape measure and i quote ''is a precision clearance gauge for the measurement of clearance between fitted surfaces''.
cant see why youd need it if youve got a micrometer and feeler blades,
am i missing something? :-\
micrometer and feeler gauges are metal, and if used incorrectly can actually damage the surfaces that they are measuring the gap between
You also need full access to both surfaces so you can insert the micrometer "feelers" or the feeler gauge "tongue" ... plastigauges get around this access problem, especially when trying to measure bearing surface clearances, when access would be extremely difficult.
Imagine trying to get feeler gauges/micrometer to measure the clearance in a split bearing !!
.... such as a big end bearing, once fitted and torqued to the crankshaft. Plastiguage can measure extremely fine tolerances without damage or human error and only requires component disassembly to read what the clearance is. :y
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thanks guys.
ok so say im measuring the distance between a big end bearing shell and the cap.... i'd put a plastgauge up to measure it.... isnt it then prone to it being wrong anyway as its all by eye?
sorry if all this sounds stupid but ive never used one :y
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thanks guys.
ok so say im measuring the distance between a big end bearing shell and the cap.... i'd put a plastgauge up to measure it.... isnt it then prone to it being wrong anyway as its all by eye?
sorry if all this sounds stupid but ive never used one :y
you would put a plastigauge between the shell and the cap, the torque up the bolts to the correct torque. then undo the lot and observe the plastguage against the scale given.
The plastigauge starts off round, and is squashed/deformed by the exact amountto end up fitting in the clearance gap. so it tells you the size of the clearance gap. if it is correct, just reassemple and retorque to EXACTLY the same value you used the first time ... :)
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Got some here, its a controlled cross section tube of what is basically a form of plasticine. When you squash it it gets wider and by measuring the width of the squashed material you can determine the clearance
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Aaaaaaaaaaaaaaaaha! i now understand..... i thought it was a tape measure type thing :-[
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http://www.youtube.com/watch?v=ulDX9Y4n0e0
Might help understanding ... :) but is fairly crap TBH
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Right, got ya. thanks boys :y
handy piece of equipment then :y
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Aaaaaaaaaaaaaaaaha! i now understand..... i thought it was a tape measure type thing :-[
the clue is in the name ...... plasti(cine) gauge ;) ;) ;)
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Aaaaaaaaaaaaaaaaha! i now understand..... i thought it was a tape measure type thing :-[
the clue is in the name ...... plasti(cine) gauge ;) ;) ;)
;D ;D ;D ;D i know. sometimes you cant see the wood for the trees ::) ;D ;D ;D
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....
;D ;D ;D ;D i know. sometimes you cant see the wood for the trees ::) ;D ;D ;D
you'll get there ..... :y
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Excellent :y Never heard of that and good to know :)
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Proper Haynes manuals actually referenced it in mechanical overhaul guides, and gave the relevant clearance specs for bearing shells and the like :y
None of that 'refer to dealer' rubbish that you get in the modern ones :-\
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Bearing clearances for bigs and mains are all pretty much the same across all engine applications, 3/100-5/100mm (1-2 thou for Andy B :y), the rule we used to work to is 1/100mm per 10mm of crank journal diameter (or 1 thou per inch).
When blueprinting an engine, you move bearings around until you get optimum clearance on all bearings.
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Thanks Mark ;)
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Speaking of.. I read recently one (well respected, if I'm remembering the source correctly) engine builder stating that plastigauge was as useful as a chocolate teapot, and the only way to measure bearing clearances properly was using a micrometer and bore gauge.
If I recall the procedure correctly it was; measure the main bearing shell with the bore gauge (after torquing down the cap), then measure the journal with the micrometer, zero the mic and then measure the bore gauge; that reading is then the clearance..
Wish I could remember where I read it now, whether it was in Barry Rabotnik's book or whether it was Mike Huddart.. the former being much less reliable than the latter!
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Speaking of.. I read recently one (well respected, if I'm remembering the source correctly) engine builder stating that plastigauge was as useful as a chocolate teapot, and the only way to measure bearing clearances properly was using a micrometer and bore gauge.
If I recall the procedure correctly it was; measure the main bearing shell with the bore gauge (after torquing down the cap), then measure the journal with the micrometer, zero the mic and then measure the bore gauge; that reading is then the clearance..
Wish I could remember where I read it now, whether it was in Barry Rabotnik's book or whether it was Mike Huddart.. the former being much less reliable than the latter!
On those old yankee lumps you can measure the clearance with a tape measure, surely? ;)
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Nah.. If you can get your fingers between the journal & bearing it's worn, if you can't then it's good for another 200k.. ;D
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Nah.. If you can get your fingers between the journal & bearing it's worn, if you can't then it's good for another 200k.. ;D
Makes sense. Too many damn 'nummers on the tape measure. ;)
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save posting a new thread.... ive been learning about thrust bearings.
am i right in thinking they are located along the main bearing journals in the block to locate the crankshaft laterally.... and that you can test it by pressing the clutch pedal and measuring forward crankshaft movement to see if theyre shot? well if thats the case how can you test it on an auto? and am i right in thinking that thrust bearings are poor on omegas? (just remember someone mentioning it :)
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save posting a new thread.... ive been learning about thrust bearings.
am i right in thinking they are located along the main bearing journals in the block to locate the crankshaft laterally.... and that you can test it by pressing the clutch pedal and measuring forward crankshaft movement to see if theyre shot? well if thats the case how can you test it on an auto? and am i right in thinking that thrust bearings are poor on omegas? (just remember someone mentioning it :)
Clutch pedal will show you some of the play,better to grab the crank pulley and push/pull it in and out(engine off naturally :D :D)
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save posting a new thread.... ive been learning about thrust bearings.
am i right in thinking they are located along the main bearing journals in the block to locate the crankshaft laterally.... and that you can test it by pressing the clutch pedal and measuring forward crankshaft movement to see if theyre shot? well if thats the case how can you test it on an auto? and am i right in thinking that thrust bearings are poor on omegas? (just remember someone mentioning it :)
Clutch pedal will show you some of the play,better to grab the crank pulley and push/pull it in and out(engine off naturally :D :D)
;D ;D ;D
can you do that with an auto? i presume you can :-\
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save posting a new thread.... ive been learning about thrust bearings.
am i right in thinking they are located along the main bearing journals in the block to locate the crankshaft laterally.... and that you can test it by pressing the clutch pedal and measuring forward crankshaft movement to see if theyre shot? .....
Pushing the clutch loads up the thrust bearing which is why it's not best practice to press the clutch as you start ...... however on lots of manual cars these days you have to press it to start the car
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save posting a new thread.... ive been learning about thrust bearings.
am i right in thinking they are located along the main bearing journals in the block to locate the crankshaft laterally.... and that you can test it by pressing the clutch pedal and measuring forward crankshaft movement to see if theyre shot? .....
Pushing the clutch loads up the thrust bearing which is why it's not best practice to press the clutch as you start ...... however on lots of manual cars these days you have to press it to start the car
i know about that. when i worked in edinburgh for a couple months the girls i work with were late. get a call at half 9 ''we cant start the hire car'' ::) ::) ::) ::) ::) ;D
how much movement roughly would be acceptable?
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and presumably when we measure end float, this is what we're really testing? :)
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how much movement roughly would be acceptable?
Errr? Not sure really :-\ There'll be limits quoted somewhere. It won't be that much because the thrust 'bearings' are only white metal ..... like a main/big end.
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and presumably when we measure end float, this is what we're really testing? :)
yes :y :y
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got ya!!!! cheers andy. so basically just look at the end float tolerance and thats your thrust bearing test :) :) :)
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Thrust bearings are often incorporated into one of the main bearing shells, i.e. the inside of the shell forms the main bearing, and it has an additional thrust surface on either end of the bearing which runs between 2 faces machined on the crankshaft.
Haynes manual gives maximum crank endfloat for the V6 as 0.05-0.15mm.
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Thrust bearings are often incorporated into one of the main bearing shells, i.e. the inside of the shell forms the main bearing, and it has an additional thrust surface on either end of the bearing which runs between 2 faces machined on the crankshaft.
Haynes manual gives maximum crank endfloat for the V6 as 0.05-0.15mm.
Bit like this:
(http://pitstopusa.com/images/F14608104.jpg)
Thrust bearing top left, regular bearings are the rest..
Good pictures of how they'd fit in here: http://www.ffcars.com/forums/2475069-post34.html
End measuring endfloat the 'right' way: http://www.ffcars.com/forums/2485122-post36.html
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Ahh, was just thinking some pictures would help. :y
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Ahh, was just thinking some pictures would help. :y
I nearly went out and took a photo of the bottom of my 428 .. then remembered how heavy it is with the heads bolted on and just lifted some from a favourite thread instead ;D
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;D
got ya lads.
this video was pretty useful too. but I like to discuss things on here cos not everything on youtube is accurate :-X ::) ;D
http://www.youtube.com/watch?v=Vdl7texNgBk