Neville Jones
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| posted on 25/6/11 at 06:39 PM |
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quote:
Your ignorance of steering geometry is priceless.
Only outdone by your very self. Think before you write! 
Oh dear, dear, dear, he thinks he's an engineer, ......again!
Considering I do this design work for a good chunk of my living, yes it is priceless to you anyway, you could never afford me! I've said
before, I cannot be considered underfed or underweight, so someone must think I'm worth paying. 
Caster is the angle between the top and bottom ball joint and vertical, when viewed from the side. Right?
Some one tell me if this bit of basic car design has been rewritten in the last week, please?
Moving the 'mushroom' around, doesn't move the ball joint at all, so doesn't affect caster.
What moving the mushroom DOES do, is change where the axle sits relative to the line joining the top and bottom ball joints.
Changing KPI affects scrub, which affects kickback, and a couple of other bits which I mentioned. Certainly doesn't help self centering.
Changing caster affects the longitudinal kingpin offset, or contact patch trail, which directly affects the centering force acted on the contact
patch, and the resulting moment about the kingpin line. Self centering force.
Now Mr.BT, tell me where what I've just put is wrong, and why.
Cheers,
Nev
[Edited on 25/6/11 by Neville Jones]
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loggyboy
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| posted on 26/6/11 at 02:34 PM |
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quote:
Moving the 'mushroom' around, doesn't move the ball joint at all, so doesn't affect caster.
Surely it does move the angle at which the upright sits, which in turn changes the route in which the upright moves when steering input is made.
It doesnt matter if you move the bottom or top joint of an axis.
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Neville Jones
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| posted on 27/6/11 at 10:05 AM |
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quote:
Moving the 'mushroom' around, doesn't move the ball joint relative to the lower ball joint at all, so doesn't
affect caster.
What moving the mushroom DOES do, is change where the axle sits relative to the line joining the top and bottom ball joints.
Think of how a supermarket trolley wheel runs, behind the vertical line it rotates about. This is trail. If the axle is behind the line joining the
upper and lower ball joints, then the car will have trail, which will help self centering. This isn't a highly recommended practice, but will
work to help some of the problem.
Ultimately eventually, the fix is to give the car about 5~7 degrees of caster, by making the changes as put above in my post.
IVA stations have been made aware of the bodges used(toe out and tyre pressures), and will now be looking for them and failing cars on that basis.
Cheers,
Nev.
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