alistairolsen
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| posted on 16/3/09 at 04:00 PM |
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quote:
Originally posted by procomp
Hi
When will the KIT manufacturers actualy sort the problems out rather than leaving customers who have spent a large amount of money with them. With a
car that will not legally pass the SVA / IVA test without being bodged.
It really is appalling.
Cheers Matt
That too!
I was thinking as a "from scratch" builder and forgot about the kits!
Was shoving one of your chassis round knockhill in the wet a couple of weekend back! Had a look in the pits, really nice car!
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twybrow
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| posted on 16/3/09 at 10:39 PM |
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Dave/Al - My point is, we have all heard that remaking the wishbones and/or moving the suspension brackets seems to be the way to go. However, as so
many of us are desperately trying to get legal before the IVA, my point was, new 'bones would probably be on the list of post SVA jobs.
I'm not suggesting bodging, then forgetting, far from it, but I bet there were a few shortcuts you both took to ensure an SVA pass....!?
[Edited on 16/3/09 by twybrow]
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David Jenkins
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| posted on 16/3/09 at 11:28 PM |
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quote:
Originally posted by twybrow
I bet there were a few shortcuts you both took to ensure an SVA pass....!?
Only cosmetic ones - and some of those are still on the car! The only significant one was the Sierra steering wheel, which came off as soon as i got
home (I couldn't get my legs under it...).
I was lucky with the wishbones - I'd heard about the problem before I made my own, so I was able to build in the correct offset from the
beginning.
Fair comment about getting through the SVA - but the testers are wise to some or all of the tricks, and also the builder should realise that it will
need fixing after the test.
The previous comment about the kit builders sorting themselves out is the main thing - how long would it take them to remake a wishbone jig? One hour?
Then all these problems would vanish.
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nitram38
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| posted on 17/3/09 at 05:16 AM |
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The trouble with the "tone" of the toe out advice is that it tends to give the impression that it is a normal setting. The person who
built the car who is short of time, wants a quick fix, but who wants to turn up to sva and fail?
I tried all of the toe out/pressure fixes and I even considered the springs on the steering rack, but I drove my car and it was scary coming out of
bends, the one place you really need stability.
I simply bit the bullet and got on and remade the top bones. Not only was it a final fix, it transformed the handling.
I may not be telling people what they want to hear, but what they need to hear and should act on.
Giving toe out advice to someone who then goes and stuffs their car the first time they give it some beans would make me feel pretty sick, to be
honest......
[Edited on 17/3/2009 by nitram38]
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procomp
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| posted on 17/3/09 at 08:05 AM |
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Hi
what many do not seem to realise is that Castor dose far more than simply help the self centering effect. Now given that these manufacturers claim
they have chassis that have 5 deg of Castor built into them. Why is it that when measured and checked the majority only have 2-4 deg on them. And
given that this results in the finished product not being able to legally pass the SVA / IVA and actualy be legally road worthy. Particularly when a
manufacturer actualy tells there customers how to bodge it through illegally.
It makes you wonder just where the customer stands legally whith the manufacturer. Just thinking about the court case with a certain manufacturer and
his floating cars that did not meet the regulations is was meant too.
Cheers Matt
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mads
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| posted on 17/3/09 at 11:27 AM |
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ok, how out of curiousity will the MK spec R chassis have this issue? If so, what can I do NOW before I start putting it together?
(I have no welding skills so making something is out the window)
We gain knowledge faster than we do wisdom!
Life is not a journey to the grave with the intention of arriving safely in a pretty and well-preserved body, but rather to skid in
sideways, thoroughly used, totally worn out and loudly proclaiming... "f*ck, what a trip!"
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twybrow
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| posted on 17/3/09 at 11:30 AM |
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Speak to MK and find out... They said the R was a fully CAD designed chassis, so I assume (and you know what they say about assumption) that they
could give you the castor angle over the phone....
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flak monkey
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| posted on 17/3/09 at 08:33 PM |
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You need about 22mm offset on the top bone to give the right amount of castor IIRC on a book chassis.
Having said that my GTS self centres beautifully with much less offset than that (about 15mm) and a very small amount of toe out and a fair bit of
camber (essentially the caterham setup)
David
Sera
http://www.motosera.com
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David Jenkins
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| posted on 17/3/09 at 09:07 PM |
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There are other factors alongside castor angle, such as stiffness of steering joints and the steering rack. If the steering mechanism is stiff then
even the correct castor angle will struggle to self-centre. On the other hand, a marginal castor angle will have an easier time if the mechanism
moves freely. So one action would be to ensure that everything runs as free as possible, but without introducing play.
The other thing that may be possible is to use the spacing washers to move the lower wishbones as far forward as possible (1 at the front, and fill up
the remaining space at the back with the remaining ones), and do the opposite at the top to move the top wishbones as far back as possible. This is
assuming that your brackets and wishbone bushes require a stack of washers during assembly! You might gain an extra degree of castor, which might be
enough to get things working.
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