Omega Owners Forum
Chat Area => General Car Chat => Topic started by: feeutfo on 08 April 2013, 22:37:53
-
...to an omega.
Discuss.
I'm assuming more control, more direct steering input. Loosing the steering idler, and that notchy rubber square damper between column and box.
Although some steering racks can be quite notchy, pulse, and do odd things in themselves, if my mondeo was anything to go by.
The rats omega had a rack from a Nissan Almeria iirc. So, with 1000bhp on tap I'm thinking that would be good enough.
And why is it better to have a steering rack in front of the drive wheels, not behind, as it would have to be on an omega...?
:)
-
What does the Omega have as opposed to a steering rack? I assumed ''steering idler'' was just an oof term for steering rack :-[
-
What does the Omega have as opposed to a steering rack? I assumed ''steering idler'' was just an oof term for steering rack :-[
When you have a few more pennies, get yourself this book and become top of the class.
http://www.amazon.co.uk/Light-Heavy-Vehicle-Technology-Nunney/dp/0750638273
-
What does the Omega have as opposed to a steering rack? I assumed ''steering idler'' was just an oof term for steering rack :-[
Omega uses a "steering box" to give full power steering - try driving the car when being towed with the engine stationary and you'll know it !!
Steering rack is short for "rack and pinion" steering ... may I suggest a read here will explain it all much better than I can .. :)
http://www.carbibles.com/steering_bible.html
-
What does the Omega have as opposed to a steering rack? I assumed ''steering idler'' was just an oof term for steering rack :-[
When you have a few more pennies, get yourself this book and become top of the class.
http://www.amazon.co.uk/Light-Heavy-Vehicle-Technology-Nunney/dp/0750638273
I think that book (or lots similar are in the library at school :y :y We haven't covered steering yet though sadly so was just wondering :)
-
What does the Omega have as opposed to a steering rack? I assumed ''steering idler'' was just an oof term for steering rack :-[
Omega uses a "steering box" to give full power steering - try driving the car when being towed with the engine stationary and you'll know it !!
Steering rack is short for "rack and pinion" steering ... may I suggest a read here will explain it all much better than I can .. :)
http://www.carbibles.com/steering_bible.html
cheers mate. ill read up :y :y :y
-
What does the Omega have as opposed to a steering rack? I assumed ''steering idler'' was just an oof term for steering rack :-[
When you have a few more pennies, get yourself this book and become top of the class.
http://www.amazon.co.uk/Light-Heavy-Vehicle-Technology-Nunney/dp/0750638273
Oi steady on, its a fair question. Assuming I've read that as intended.
-
Rack in front of wheels would put driver input ahead of road reaction figuratively and literally. Rear mounted would add a level of damping against road inputs, and therefore improved control :-\
Ultimately though, front or rear mounting is pure packaging compromise :y
-
What does the Omega have as opposed to a steering rack? I assumed ''steering idler'' was just an oof term for steering rack :-[
The idler is actually a component part, and I only know that because my MFL failed the mot one time because of it. I ended up changing it myself (with OOF guidance of course) because my mechanic had never heard of it! I'm wondering now though if it is specific to cars with no rack, where in those days I just thought he was stupid :-X
-
Idler and steering box are simply swapped positions, to account for left and tight hand drive cars. The mounting holes are the same in the chassis rail.
Accounting for akaman(?) wheel positions so the inside wheel turns tighter, as it should, presumably means the rack must work on the exact same plain as the centre drag link on omega?
Re position front or rear, I'm having trouble seeing how the leverage from the road wheels and road imperfections feeding back to the driver through the steering, can be affected by the hub arms leading forward or trailing rearward...? Neither can have an effect on when the wheel hits a bump or road imperfection. The leverage is the same. To my mind. :-\
-
Currently, I can't see it (rack position for or aft) making any odds, other than where the rack will physically fit, given current infrastructure.
-
http://passionford.com/forum/restorations-rebuilds-and-projects/231097-zzz-zzz-sleeper-granada.html (http://passionford.com/forum/restorations-rebuilds-and-projects/231097-zzz-zzz-sleeper-granada.html)
To save rummaging tail end of reply #7 :y
Subframe mounts at front of the chassis rail and aboot halfway down the inner wing. Double wishbone fully independent set up.
Rear suspension basically the same as the Omega with out the tie rods, so arguably a poorer design :-\
-
Steering racks and boxes are both gear systems. Properly setup, there is no theoretical advantage to either. Replacing a properly engineered box with a properly engineered rack isn't going to make any appreciable difference to the driver.
Racks tend to be more compact, but packaging a rigid 1.5m rod across the front of the car can be quite challenging, especially in a RWD car. This is why you see both front and rear mounted racks. RWD Escorts have it in front of the cross member, Avengers at the back. Both are similar sizes, with strut front ends.
The extra linkages that a box requires can make the packaging easier; the Pitman arm(and attendant idler arm on the otherside) can be used to space the centre tie rod up or down as necessary. A Superminx for example has the centre rod running along the bulkhead above the bell housing.
In use, you tend to find that boxes are more robust/durable, but the linkages wear; whereas wornout racks aren't particularly unusual.
Replacing a box with a rack is probably best considered an interesting engineering exercise rather than a practical thing to do.
-
There are sound space saving reasons, for this thread. ;)
-
Been digging through my Haynes collection ::)
Mk2 Granada front suspension, whilst an antiquated design, is completely self contained, so could in theory at least, be bolted onto any chassis of a suitable width. Two horizontal bolts each side through the chassis rails approx 18" apart.
Mk3 Granada, and Sierra front suspension is McPherson based. Accurate location for geometric precision essential and difficult. Both cars have the same subframe with longer arms on the Granada. Two vertical bolts either side into the chassis rails approx 5" apart.
All three cars have the rack mounted ahead of the wheel centre line, and use an intermediate shaft to connect to the column. All three available with or without power steering. The later design runs the ARB back to the chassis rails, where they drop beneath the floorpan. The earlier design keeps everything forward of the wheel line allowing a shed load of space for V8 stylee exhaust systems, the only considerations being the actual chassis width, front hub/brake details, adjusting the intermediate steering shaft to suit and finally suitably rated springs.
-
Mk2 Granada front track 1515mm
Omega front track 1514mm...
-
Re position front or rear, I'm having trouble seeing how the leverage from the road wheels and road imperfections feeding back to the driver through the steering, can be affected by the hub arms leading forward or trailing rearward...? Neither can have an effect on when the wheel hits a bump or road imperfection. The leverage is the same. To my mind. :-\
Perhaps :-\ I was thinking out loud tbh...
Worth noting that the vast majority of wwd cars have the rack fitted at the bulkhead/behind the wheel centreline, whereas, rwd cars with racks tend to have it fitted to the subframe, and quite often in front, using an intermediate shaft to connect the rack with the column.
Another detail to consider, is that the Omegas' steering box supports the base of the column, whereas a rack might not :-\
Holden mount the rack behind the subframe, again with an intermediate shaft, but I can find no detail for the column itself :-\
-
I think rack in front or rack behind influences the dynamic behaviour of the suspension. Assume, for a minute, that you locate the rack such that the track rods are parallel to the ground at the car's normal ride height.
If you brake, the suspension will dive at the front, the track rods now end up inclined upwards towards the knuckle, reducing their effective length. If you accelerate and the rear of the car settles, weight is transferred to the rear and the front rises. Same effect, the effective rod length reduces. Depending on the interaction between the arc the rod goes through and that of the suspension arms, you'll get a little toe-in or toe-out. Put the rack behind the wheels and you'll get the opposite. If not controlled, this effect will give you bump-steer.
I've no idea how you'd set up all these little subtleties to get a car that drives in a reasonably refined manner, but I'm sure you'd have to. I know this having had to play around with ride height and the exact position of the rack on the Westfield to get it to play nicely.
On a FWD car you've got longitudinal forces from the driven wheels acting on the suspension in acceleration in addition to braking, so I can imagine the rules are all different.
I would imagine that, to get anything drivable by your standards out of a rack setup, you'd need to give 2woody a calculator, quite a bit of paper, and a LOT of beer. ;)
-
So would it therefore be prudent to fit an entirely self contained set up such as the Mk2 Granada one :-\
Spring rates/bushes being tweaked to allow for Omega/V8 weights (given that is obviously the desired outcome::)
-
Thanks for all the info... sorry didn't mean to digress from the original question and hijack your post, Chris :-[ :)
-
So would it therefore be prudent to fit an entirely self contained set up such as the Mk2 Granada one :-\
But you'd still have to tweak it such that the pivot points of the track rods are in the right place relative to the lower wishbone pivot points (vertically and horizontally) to avoid excessive bump-induced-toe..
To give an idea of the sensitivity; one particular marque of Cobra replica had (in the past) quite hideous bump steer that someone described as 'frightening' - removing just 10mm of metal from the mounting posts of the rack to move the whole rack upward transformed it and reduced the bump-steer to near zero.
So you've got to hope that the Granny rack has the track rod pivots in the right place, or you end up doing a cut'n'shut on the rack (also used to be quite common in the past on kit cars, before that kind of thing was deemed 'undesirable' and manufacturers started having people like Quaife make bespoke racks to suit their exact suspension geometry).
If doing a cut'n'shut is feasible (technically and mechanically speaking, it is) then you want to find a rack slightly longer than you want that has the input shaft in the right place, and then chop it up, re-weld the insides, machine them and weld the rack back together..
IMHO, etc :)
[edit] Wait a second, I see what you're saying now - basically ditch the front subframe of the Omega and fit the whole lot from the Granny? Subframe, suspension, mounts, rack, etc etc..
That could work, too. I'll shut up now ;D
-
Got there in the end Aaron :y
Geometry will be fine as long as the subframe is mounted squarely :y only packaging issue is running the exhaust around the intermediate steering shaft, although with nothing behind the subframe, no steering box/tie rod/idler, there should be a shed load of space to play with :y
-
Interesting gents. As Al says, the space saving aspect of this is purely to keep an ecpensive v8 away from the steering. There's no sense in spending large sums on an engine like that to mess about with off centre position and clearance issues.
So purely with that in mind, initially, I'd be happy to replicate the existing set up but with a rack. Rear position, behind the subframe in the same position as the centre tie rod, and have the ball joint pivot points in the same place as required.
But thinking further, the front polly bush gives way more control it seems, so after talking to 2woody, it seems the front mounted rack would have something much firmer and accurate to pull against, and therefor transmit the steering to the hub more directly.(this is way too simplified a statement but gives an idea on his general description he gave, some of which I even understood) where as the rear rack would push the rear of the hub out, as opposed to the front of the hub in. Wouldn't make the slightest odds if the bushes where not bushes but solid rose joints/or points, but through a rubber or poly bush that gives more comfort, and therefor some play, then the front mounted rack gives a much more direct toe in to the outside wheel that does most of the turning in
of the car.
This is considered worth having, in design terms, as I understand it.
So logic might then be, that if fitting a rack at all, fit the bugger in the best place. Although there's a lot more extra work involved. Swapping hubs to opposite sides so the ball joint fixes to the front. Longer brake hoses as the calipers will then be at the back.... probably fouling the wishbones thinking about it. Aaaaaah ;D
...my thoughts are I'd be happy to achieve the same performance with a rear mounted rack. But depending on the work load, front mounted might be worth having.... If there's room under the sump area. :-\
-
Interesting gents. As Al says, the space saving aspect of this is purely to keep an ecpensive v8 away from the steering. There's no sense in spending large sums on an engine like that to mess about with off centre position and clearance issues.
Before you get too fixated on that one it might pay to work out* the prop shaft UJ angles with your chosen engine & gearbox combination - you might need an offset to ensure that the angles work out to ~1-3º to avoid the UJs binding or wearing the needle roller bearings prematurely..
*work out in this case probably means fitting the engine & gearbox to the car and then mocking up the prop shaft with a scrap shaft, grinder and a welder, then getting some inclinometers out. I'll concede you're unlikely to end up with an angle severe enough to bind the UJs up, but if you end up too close to 0º offset the prop won't last long.
Assuming, of course, the prop has conventional UJs at either end and not something strange and exotic.
So much to consider if you want to do it all 'properly', but the best place to start is sticking and engine in an empty shell.. :P
-
That's the thing though, theres a bloody great steering box in the way.
... And an abs pump. Bah, minor issue. :)
-
The problem(s) I see with simply replacing the current setup with a steering rack and maintaining the geometry are as follows:
1) You'll need a steering rack that places the inner track rod pivots at exactly the same place as they currently are, so it will need to be cut and shut. You then need to work with wherever the steering column needs to attach to it, and where its' mountings need to be so more hacking about needed there.
2) The shaping of the centre tie rod in the current setup is done to add clearance around the bellhousing. With a rack, you have the constraint that there must be a straight line between the two inner track rod ends, so this will actually lose you clearance.
I'd want to have offered up an engine and made absolutely certain that it won't ever fit before suffering that pain. If a slightly asymmetrical engine position would achieve it, I'd be delighted. It's really only an aesthetic issue, after all. Look at how many FWD cars have a seriously lop-sided engine bay!
ABS pump is a day's work with a flaring tool to move anywhere in the car. It's even doubtful that you'd be able to use the original one due to its' level of integration with the engine and autobox ECUs.
-
Hence my suggestion ::)
-
There's no doubt in my mind tbh. Box has to go. Project is a non starter otherwise.
-
The rats rack, scroll down. :)
http://www.rats.no/omega_tg.html
-
Are you going with a Lexus lump, or something else? Thats the first thing to consider.
I'd expect the box/idler to be easier to accomodate than a rack.
-
If its just a rack for the sake of a rack.....
-
Search dtm cars. Eg audis or v8 supercars. Think most teams use electric racks now days.
-
If its just a rack for the sake of a rack.....
I wonder ::)
-
Are you going with a Lexus lump, or something else? Thats the first thing to consider.
I'd expect the box/idler to be easier to accomodate than a rack.
Ls1 or similar.
Well, yes. It would be, as that's the original design.
...and yes it is just a rack. But for the sake of 3 inches width in the engine bay.
You'll note the title. "Fitting" a rack. There is no, "not Fitting" a rack. Lets have a more positive approach aye? >:(
-
Are you going with a Lexus lump, or something else? Thats the first thing to consider.
I'd expect the box/idler to be easier to accomodate than a rack.
Ls1 or similar.
Well, yes. It would be, as that's the original design.
...and yes it is just a rack. But for the sake of 3 inches width in the engine bay.
You'll note the title. "Fitting" a rack. There is no, "not Fitting" a rack. Lets have a more positive approach aye? >:(
Right sized rack will fit absolutely no problem .... :)
(but you might find fitting the engine afterwards a tad trickier .... )
Positive enough for you ... ??? ??? ??? ;D ;D ;D ;D ;D ;D ;D
-
Are you going with a Lexus lump, or something else? Thats the first thing to consider.
I'd expect the box/idler to be easier to accomodate than a rack.
Ls1 or similar.
Well, yes. It would be, as that's the original design.
...and yes it is just a rack. But for the sake of 3 inches width in the engine bay.
You'll note the title. "Fitting" a rack. There is no, "not Fitting" a rack. Lets have a more positive approach aye? >:(
Chill Pill ;)
Some threads are "I want to use Castrol Oil/Falken tyres". Note, NOT "I dont want to use Castrol Oil/Falken tyres". The whole point of an interactive forum is to gain/share ideas, either wacky, inspirational or just plain sensible. Live with it. >:(
I was the GM Omega V8 (not the omegav8.com) a rack or box. I thought it was the latter. I was thinking more along the lines of if GM have already done all the hard work, and pretty much proved it all worked well... ...but what would they know ;)
Sorry if I misunderstood.
-
As you wish. :)
-
Opps. Guess I did read it right.
No point continuing discussion now, so locking.