jcduroc
|
| posted on 2/1/04 at 03:45 PM |
|
|
quote:
Originally posted by dozracing
Thinking about this logically, it doesn't matter how you put the mushroom in, the castor angle is determined by the centre of the balls of the
ball joints top and bottom. The mushroom insert can be in any orientation and it doesn't effect the ball joints position and therefore cannot
effect castor, or indeed the steering feel.
Kind regards,
Darren
I can not resist quoting this statement.
You have a "mushroom" with an excentric hole by as much as 5 mm (so Bob says) and if you turn it it does not affect the position of the
balljoints and therefore the caster (and camber)???
Darren, explain us that!
JCM
|
|
|
|
|
Mix
|
| posted on 2/1/04 at 05:28 PM |
|
|
Kingr
I agree, but I think the results would be insignificant.
JC
You have two ball joints fixed longitudinally and laterally in space, (by the wishbones). (This is a loose description but good for this case).
Turn the eccentric any way you will, all that will happen is the inclination of the upright will change.
Good thread though
Mick
|
|
|
kingr
|
| posted on 2/1/04 at 05:39 PM |
|
|
Mick,
Yup, agreed, they'll be pretty marginal, it depends on the initial castor angle and the distance between the ball joints. I think the crux of
the matter is that you couldn't call it adjustability, more just a (very slight) side effect.
Kingr
|
|
|
stephen_gusterson
|
| posted on 2/1/04 at 08:22 PM |
|
|
surely, as you rotate the excentric hole thro 4 steps of 90 degrees, you will get 2 positions where camber is affected and 2 where castor is
affected.
suspension issues are always ba$#ards are they not 
atb
steve
|
|
|
Alan B
|
| posted on 2/1/04 at 10:52 PM |
|
|
I'll state my opinion again...which I strongly believe to be correct.....
Castor ANGLE is not changed, but the "castor" effect is changed due to the fore and aft movement of the wheel relative to the castor angle
line's intersection with the ground. (trail)
Also, I would disagree with Mark? (I think) in that KPI is not changed as the BJ centres don't move.... however camber is changed of course.
Bottom line..... the BJ centres don't move.....KPI and castor are measured using BJ centres so therefore they do not move either.
I do agree though...good thread..
|
|
|
Mix
|
| posted on 3/1/04 at 08:53 AM |
|
|
Another observation
Now that we seem to be seeing light at the end of the tunnel on this one has anybody considered the effect that rotating the eccentric will have on
bump steer ??
Mick
|
|
|
dozracing
|
| posted on 3/1/04 at 12:11 PM |
|
|
Been thinking about this again this morning, i haven't got a Sierra upright to look at but, if the castor line thru the ball centres is off set
from the wheel centre then it will make a small difference to trail.
On a cortina upright wherre there is no offset it would make no difference.
On our kit we use an concentric mushroom, and put the desired camber in the top wishbone.
Kind regards,
Darren
|
PLEASE NOTE: This user is a trader who has not signed up for the LocostBuilders registration scheme. If this post is advertising a commercial product or service, please report it by clicking here.
|
Mark Allanson
|
| posted on 3/1/04 at 01:01 PM |
|
|
Alan, what I meant about KPI was if you change the offset of the top balljoint the camber will change, but to reset your camber to its original
setting, you would have to alter the balljoint positionrelative to the car and therefore altering the KPI
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
|
|
|
JoelP
|
| posted on 3/1/04 at 01:08 PM |
|
|
alan has it COMPLETELY right IMHO.
i was gonna post in my first post that you would have to go back to basics and work out why castor angle affects self centering.
the gist of it, in my opioion, is that trail causes selfcentering, and one way of making trail is to lean the hubs back. other ways are possible,
namely by moving the center of the hubs rotation back so it is behind the axis of steer. this is what happens when the mushroom is rotated.
so technically, if you define castor angle as the angle between the two balljoint and vertical, the mushroom does not affect this, even though it will
increase trail.
|
|
|
Alan B
|
| posted on 3/1/04 at 02:10 PM |
|
|
Mark....I see what you mean...readjusting the top BJ to correct the camber change caused by the mushroom will change KPI..agreed.
Joel..Good at least two of us agree..
|
|
|
dozracing
|
| posted on 3/1/04 at 07:23 PM |
|
|
Essentially i think we have found all figured the correct reasoning.
I think though that the eccentric adjuster is a poor solution, better to put the desired castor/camber/KPI in your basic layout than in an eccentric
bush. If you have the eccentric bush loaded laterally the force acting on it will want to twist the bush and so alter your geometry.
Its also a lot more expensive to make them eccentric as you then have to mill them or use more sophisticated off centre tooling in your lathe.
Kind regards,
Darren
|
PLEASE NOTE: This user is a trader who has not signed up for the LocostBuilders registration scheme. If this post is advertising a commercial product or service, please report it by clicking here.
|
