Marnoldsson
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 posted on 5/11/14 at 11:30 PM |
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Shortening of power steering Sierra rack
Good evening.
I am writing from Sweden, I am in the middle of a MK Indy based project, actually its a Lotus Elan body fitted on a MK Indy chassis, or at least the
suspension bits from an Indy since Ive modified everything else long from recognition.
Anyways, the steering rack, it needs shortening. I have a servo unit which I intend to shorten, but not really know how much
? As it is now the rack has something in range of 400mm cc from the mounting holes but the chassis got cc 150mm, that is somewhere around 25cm of
shortening, I find it pretty much.
I know I can measure this from the wishbone pickup points, but thought that someone here maybe could tell me instead
Does anyone has the CC measure inner steering joints?
The suspension bits is somewhere around 2003 model, no pushrods etc. Are there any alternatives chassiwise, or are they all the same?
I know that many of you will tell its a bad idea shortening a servo unit, but 2.5 turning lock to lock and a couple of thousand miles maximum a year
makes it worth a try in my opinion.
Thanks for the help!
Magnus
[Edited on 6/11/14 by Marnoldsson]
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Marnoldsson
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| posted on 7/11/14 at 08:42 AM |
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noone?
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adithorp
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| posted on 7/11/14 at 01:03 PM |
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As your only using the MK running gear and your chassis is custom (rather than original Indy) then surely, only you can know how long it needs to
be.
Add that using and shortening a power rack is a pretty rare thing to do, I doubt anyone else has tried it.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Marnoldsson
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| posted on 7/11/14 at 09:21 PM |
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Now when I see what I have wrote I can clearly understand that noone answered. To make it more clear, the complete front suspension, width and
everything is exactly like a standard MK. So all pick up points and everything is the same as in a seven. So the cc measure from inner steering joint
left to inner steering joint right is what I am after!
I have understood that you dont do it this way in Britain, but I know alot of people back here in Sweden who done it and ten years after are still
perfectly satisfied with the result.
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mark chandler
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| posted on 7/11/14 at 11:31 PM |
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I expect you have low replies as our cars are so light there is no need to run PAS.
Why not build with a cut down manual rack, if it is still heavy then add an electric PAS column, apart from being far simpler to implement you also
gain power as a PAS pump is always drawing power so very inefficient.
Sorry cannot help on measurements as I run an escort quick rack, took around 125mm out of this, I just measured between the wishbone mountings and cut
the rack element down to size then shorterned the outer to suit.
Regards Mark
[Edited on 7/11/14 by mark chandler]
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Marnoldsson
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| posted on 8/11/14 at 07:24 AM |
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more unclear info from me. I will just plug the hydraulic piping and run a servo rack without servo! So a PAS rack without PAS
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Camber Dave
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| posted on 8/11/14 at 08:52 AM |
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Is this what you want
To select the correct length of the steering rack inner ball joints(CC?)
Look at the chassis from the front. Imagine a line drawn between the inner wishbone pick ups.
The rack inner ball centres should also be on this line.
So if the rack were at the height of the top arms it would be the same length as the top 'beam'
And if at the height of the lower arms it would appear coincident with the lower inner pick up's.
A better method is to draw the front suspension viewed from the front.
Draw lines through each wishbone inner pick up and its outer ball joint. These lines should cross on the opposite side
of the car 1.5 to 2 meters from the hub centre.
A line drawn through the rack and trackrod ends should also go through the 2 metre instantaneous centre.
For both methods at the trial build the system should be checked for Bump steer (after checking Castor!)
Hope this helps
Dave
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Marnoldsson
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| posted on 8/11/14 at 09:44 PM |
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perfect. Thank you very much.
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