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  #41  
Old 18th September 2012, 10:18 PM
The V8 Files The V8 Files is offline
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Originally Posted by baz-r View Post
you cant polish a turd and rolling it in glitter is messy
Apparently you can

http://www.youtube.com/watch?v=yiJ9fy1qSFI
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  #42  
Old 19th September 2012, 12:45 AM
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Originally Posted by DRCorsa View Post
Alga, how much caster have you calculated for the original setup?
After a bit of work on CAD, i came up with this rough figure.
I assumed a vertical distance of 200.5mm between ball joints (according to this drawing) and a slight divergence between the upper and lower wishbones towards their outer ends (ball joint ends)
My "tape measure applied to the side of upright" measurement indicated the distance between balljoints is about 210 mm. I based my calculation on this length, and it works out at 5.5° then. But, this does not take KPI into account, so, looks like your numbers are more accurate.
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Last edited by alga : 19th September 2012 at 01:09 AM.
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  #43  
Old 19th September 2012, 01:04 AM
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I know you Alga may be going off a different book over there then our IVA manual, but I wonder if every one expects perfect return to dead ahead steering when pushing a car forward, it will not.
Well, I experienced no self-centering whatsoever when moving forward, at any speed. But it does self-center in reverse, and it does work by just pushing the car back with the steering at full lock. The steering wheel starts turning.

Setting to close toe to about zero did not have much effect. I'll try playing with camber next. Also, I'll try changing the wheels to the stock 14" pressed steel ones.
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  #44  
Old 19th September 2012, 09:40 AM
DRCorsa DRCorsa is offline
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alga, one thought. Maybe it's something with your steering column, maybe some awkward angle causing the steering to stuck?
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  #45  
Old 19th September 2012, 02:27 PM
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I must admit from reading this thread it does point to perhaps a more simple issue, you should always try the easy and obvious first.
I've been to 5 SVA's and IVA's we had a self centering problem on 3 this was always sorted with an adjustment of the toe on the day, none had been set up in advance just somewhere close with string and laser levels.
On the road the lack of perceived self centering has not become a problem.
We have a broad variety of cars most are 7's, Robin Hood, MK, several Locost/Haynes, only one has Cortina hubs and is still in build so can't comment on that however the Sierra hub cars are realy not a problem on the road and on some we have just shimmed the top and or bottom wishbones with washers.
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  #46  
Old 19th September 2012, 04:16 PM
wylliezx9r wylliezx9r is offline
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Originally Posted by snapper View Post
I must admit from reading this thread it does point to perhaps a more simple issue, you should always try the easy and obvious first.
I've been to 5 SVA's and IVA's we had a self centering problem on 3 this was always sorted with an adjustment of the toe on the day, none had been set up in advance just somewhere close with string and laser levels.
On the road the lack of perceived self centering has not become a problem.
We have a broad variety of cars most are 7's, Robin Hood, MK, several Locost/Haynes, only one has Cortina hubs and is still in build so can't comment on that however the Sierra hub cars are realy not a problem on the road and on some we have just shimmed the top and or bottom wishbones with washers.
I agree with you but wouldnt it be nice to have the correct amount of caster, the same as the more expensive manufacturers design in. They dont do it for nothing, it aids handling and makes the front end more planted and stable.
If somebody could come up with a new design wishbone, I for one would definately be investing in them. I cant understand why this wasnt designed in the first place. Apparently Mk Indys suffer the same.

Dan
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  #47  
Old 20th September 2012, 11:09 PM
Stumaso Stumaso is offline
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Default Caster angle

Hi ime a little confused on this one too. The offset of the upper wishbone is 23mm giving a positive caster angle of approx 7 degrees which is all you really need. So why do we need offset mushrooms. Am I missing something?
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  #48  
Old 4th October 2012, 01:51 AM
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spud69, could you chime in on the topic? You mentioned several times that you recommend the caster angle set so the car just starts to self-centre. How do you adjust the angle? What's the downside of having more caster on the Roadster?
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  #49  
Old 4th October 2012, 08:37 AM
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Quote:
Originally Posted by alga View Post
spud69, could you chime in on the topic? You mentioned several times that you recommend the caster angle set so the car just starts to self-centre. How do you adjust the angle? What's the downside of having more caster on the Roadster?
I seem to remember this has raised it's head a few times previously and yes technically you're right to bring it up again. You can turn the offset mushroom to the rear to move the steering angle forward a bit to influence the self centering. As you know it doesn't actually move the top pivot point but in my experience of the cars i've helped to set up it does help - the reason why offset mushroom started to be used. Getting the bump steer and toe fine tuned will have the best effect over stability.

I dont claim to be an expert just have some experience to use and pass on.

Cheers.......Andy
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  #50  
Old 4th October 2012, 01:44 PM
Big Vern Big Vern is offline
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Originally Posted by spud69 View Post
I seem to remember this has raised it's head a few times previously and yes technically you're right to bring it up again. You can turn the offset mushroom to the rear to move the steering angle forward a bit to influence the self centering. As you know it doesn't actually move the top pivot point but in my experience of the cars i've helped to set up it does help - the reason why offset mushroom started to be used. Getting the bump steer and toe fine tuned will have the best effect over stability.

I dont claim to be an expert just have some experience to use and pass on.

Cheers.......Andy
The mushroom should be orientated away from the engine.
The mushroom is not meant to be used to overcome the lack of caster. The mushroom takes into account the upright doesn't pivot about its centre line in the donor vehicle. Martin Keenan devised the mushroom to overcome this problem.
The lack of caster is a design flaw in my view and the design should have been corrected years ago or at least a sticky put in place so new builders would know to build in extra caster as they built their chassis. Rotating the mushroom and adding undersirable toe out to get it to self centre is just bodging round the issue.
5 degrees should be considered a minimum but some people arn't getting anywhere near as much.

Last edited by Big Vern : 4th October 2012 at 01:46 PM.
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