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  #51  
Old 4th October 2012, 01:23 PM
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Quote:
Originally Posted by Big Vern View Post
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.
You're right Vern, 7:30 this morning was a bit early for my brain working to be honest.

The roadster handles fine the way it is and you don't really want a great deal of self center, in my opinion it's mainly for lazy people driving big cars... There is nothing wrong with toe-ing out a bit more on the rack extensions just to get through IVA, although you cant do this with the mushroom (just the camber which you can also do with the threaded insert).

Suns out this afternoon and i've finished my work for the day so i'm of out in mine to see HandyAndy I'm sure it will be handling fine

Andy
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  #52  
Old 7th October 2012, 04:03 PM
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Hi Alga,
Did you sort out your self centering problem?
I've been reading up on it and it all seems a bit daunting to say the least
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  #53  
Old 7th October 2012, 11:37 PM
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No, didn't have much time to play with it TBH.

Take a look on this old thread: http://www.locostbuilders.co.uk/view....php?tid=97634
The consensus is that the proper fix is more caster, and one figure given is that 22-24 mm of displacement between top and bottom ball joints should do it (we have 20 mm standard). I'll try slackening the wishbone bushes and ensuring that their play is at the end of most camber angle.

One more idea to try from there -- rotating the mushroom a little bit inwards might increase the KPI angle (as the upper ball joint will have to be threaded further in to return the camber to where it was), while the mechanical trail will be reduced minimally. I'm not sure there will be space on the thread though -- the locknuts are already at the end of the thread, with just -2 camber and mushrooms straight ahead.

I reduced toe to zero, and now the car displays "a degree of self centering evident": if I rotate the wheel by 15 degrees, when driving, it springs back by some 3 or 5 degrees sometimes. This could be enough for IVA, but is nowhere near where I would consider it to have any safety effect.
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  #54  
Old 7th October 2012, 11:45 PM
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Quote:
Originally Posted by DRCorsa View Post
alga, one thought. Maybe it's something with your steering column, maybe some awkward angle causing the steering to stuck?
With the front up, the wheels move pretty freely, but I'll check the position of the steering rack again.
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  #55  
Old 27th October 2012, 08:22 PM
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Hi Alga,
I've made some new wishbones which you can alter the caster. I know it's of no help to you now you have yours but I thought I would show you a photo.

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  #56  
Old 28th October 2012, 10:44 AM
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Nice looking lot there . Have you had a chance to shove a caster camber guage on it yet?

Bob
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  #57  
Old 28th October 2012, 04:27 PM
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Quote:
Originally Posted by robo View Post
Nice looking lot there . Have you had a chance to shove a caster camber guage on it yet?

Bob
Hi Bob,
I don't have a camber/caster gauge.
I do own a digital spirit level which I could eye up with the ball joints I guess. or is there another way of measuring it easily.
I guess you are interested how much you can alter the caster with the rose joints forward and rearward at max?
I will try and find out tomorrow.
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  #58  
Old 28th October 2012, 09:36 PM
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Quote:
Originally Posted by Johno View Post
Hi Bob,
I don't have a camber/caster gauge.
I do own a digital spirit level which I could eye up with the ball joints I guess. or is there another way of measuring it easily.
I guess you are interested how much you can alter the caster with the rose joints forward and rearward at max?
I will try and find out tomorrow.

I have got a guage that attaches to the rim that does both caster and camber. if you need the loan of it just cover the p+p.

Bob


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  #59  
Old 29th October 2012, 08:22 PM
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Hi Bob,
Thats very kind of you... I will let you know if I need it.
I did manage to eye up the joints with my digital level with the rose joints set even and it was approx 7.4 degrees.
When I made my new wishbones I did move the top pivot rearward back 5mm which does correspond with DRcorsa's calculation of 7.14 degrees.
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Last edited by Johno : 29th October 2012 at 08:26 PM.
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