pajsh
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| posted on 22/10/05 at 09:47 PM |
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Desperate measures - Wishbones
I've worked through most of my SVA fails and just have a couple to do, one of which is the old "self centering".
I have read all the threads and tried all the fixes (low pressure, toe out etc) but basically my problem is I have zero castor. There is some small
adjustment on the top wishbone ball joint but not more than +/-5mm and I have already got this fully back (bolt fully forward).
Queston is, before I get the wishbones re-made (I can't weld) is there anything else I can do (probably not I think). I did think of buying some
Luego mushrooms but I'm not sure I would get much more out of them.
I'm also not sure how to get them altered so they will still fit but I guess my engineering man will have to work that one out.
I'm also a bit concerned my lower 'bones might not be strong enough having read the threads on bent bones. The suspension mounting point
seems quite along way in. There is a pic in my archive is anyone would wish to comment.
P.S. I bought the car as a rolling chassis and am finishing it off. It is pretty close to book but with a few "improvements!!"
Must learn to weld for the next one and start from scratch
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Mark Allanson
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| posted on 22/10/05 at 10:08 PM |
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Have you tried shimming the upper bones as far rearward as they will go, and the lower ones as far forward as they will go?
I think all the SVA testers have heard of all the bodges, on my test he said if I had done the toe out thing and the pressure dodge, he would have
failed me.
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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mark chandler
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| posted on 22/10/05 at 10:28 PM |
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That shock does look a long way in, as such lots of leverage on the lower wishbone towards the chassis.
You could sort the castor by having new lower bones that are handed by 21mm and move that mount out at the same time.
Looking at your other failures a bit of gusseting is required. Drilling, and sleaving the rear axle for a horizontal bolt and remaking the panard rod
starts to make buying your own welder a very attractive proposition (although I would not recommend building bones as a first project).
Regards Mark
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mookaloid
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| posted on 23/10/05 at 06:57 AM |
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Just had a look at your pictures, where is the hole in your mushroom inserts in the top of the front uprights?
I have seen some with the hole for the ball joint in the centre, but the ones to get are like the MK ones with an offset hole which gives more
adjustment for castor.
HTH
Mark
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Mix
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| posted on 23/10/05 at 07:52 AM |
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Here we go again
'mushrooms' with offset holes only really adjust camber as castor is dependant on ball joint centre line which does not change when the
mushroom is rotated.
I think your easiest fix would be to find somebdy who welds and to move the upper wishbone brackets rearward. There are examples on here of gusseting
and horizontal tubes between the 'L' assy and the 'FU' tubes.
Mick
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JoelP
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| posted on 23/10/05 at 09:15 AM |
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alternatively, buy some new lower wishbones that use rosejoints rather than bushes. Being narrower, you have more space to shim them. This would also
solve the shock pickup problem. I couldnt find the photo though? 
just found it. Id deffo consider new bones
[Edited on 23/10/05 by JoelP]
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britishtrident
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| posted on 23/10/05 at 10:13 AM |
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Offset muchrooms have no effect on caster To change the caster you either have alter the upper wishbones or the wishbone mounting points.
Can you post a view front suspension looking from the top down.
[Edited on 23/10/05 by britishtrident]
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britishtrident
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| posted on 23/10/05 at 10:16 AM |
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quote:
Originally posted by Mix
Here we go again
'mushrooms' with offset holes only really adjust camber as castor is dependant on ball joint centre line which does not change when the
mushroom is rotated.
I think your easiest fix would be to find somebdy who welds and to move the upper wishbone brackets rearward. There are examples on here of gusseting
and horizontal tubes between the 'L' assy and the 'FU' tubes.
Mick
Sound advice
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pajsh
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| posted on 23/10/05 at 11:41 AM |
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Many thanks guys,
Joel's idea of the rose joints sounds great to me. If I take all the bones off I can get threaded ends put on for rose joints and then do what
Mark Allanson suggested and shim the lower ones forward and the top ones back.
What size rj's would be OK? Would 1/2" UNF thread and bore be enough.
Also I may consider getting the lower bones beefed up while there off or even remade. Probably double up the tubes. I don't know if I can move
the lower shock fixing point out because the coilovers may then be too short.
Can anyone recommend some new bones that would have threaded ends and fit a book chassis as it may be cheaper and safer just to replace them.
I have taken some top down pics along with all my other SVA fixes and will upload them tomorrow from work.
Thanks again to all.
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JoelP
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| posted on 23/10/05 at 11:49 AM |
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mnr do rosejointed bones, and probably other manufacturers. You just need to measure the maximum outside gap and the minimum inside gap of your
brackets, and make sure they fit and still have room for adjustment I belive 20-25mm is the idea difference to provide a good angle with book
chassis
If you were to modify your bones, you would do well to remove the stress raise where the shock plate meets the bones at a sharp angle - you could
actually remove material and make them stronger. I would cut an arc into it and then weld on a small lip to reinforce the actual plate itself. Bear in
mind im no engineer though! 
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mookaloid
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| posted on 23/10/05 at 07:15 PM |
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quote:
Originally posted by britishtrident
quote:
Originally posted by Mix
Here we go again
'mushrooms' with offset holes only really adjust camber as castor is dependant on ball joint centre line which does not change when the
mushroom is rotated.
I think your easiest fix would be to find somebdy who welds and to move the upper wishbone brackets rearward. There are examples on here of gusseting
and horizontal tubes between the 'L' assy and the 'FU' tubes.
Mick
Sound advice
Ok Guys,
I stand corrected. I know what you say is true. Using the correct definition of castor the mushroom inserts would not change the castor angle in
whatever position they were used.
Now you can put me back in my box if you like but they would if placed correctly, have the effect of moving the position of the stub axle behind the
kingpin line (ball joint to ball joint) thereby giving an amount of 'trail' if that is the right word and so assisting with self
centering.
This is self evident if you look at things like supermarket trolley wheels which have their axles offset from the 'kingpin axis' and
therefore always end up trailing as you push the trolley forward.
IMHO of course
Mark
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JoelP
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| posted on 23/10/05 at 08:01 PM |
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you are all correct it doesnt affect literal castor but it does add 'trail'. I have called it drag in the past, but the effect is the
same.
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