about kingpin

[peaty]

hi
I'm not a chassis guy, so I'm trying to learn. I've been reading about kingping lately and I have a question...I'm pretty sure that for someone with enough knowledge my question might seems stupid, but I prefer to ask! -sorry guys-. So, by definition kingpin is "the angle, measured in degrees, that forms the line passing through the kingpin and the perpendicular to the ground looking at the vehicle from the front" right!? I have seen many race cars that use the upper rose joints to change the camber. From my understanding, they change the length of the upper arm to change camber, hence the upper rose joint moves towards the center line of the car (in the case of negative camber), am I right!? If that happens,is the kingpin changing as well!?

Thanks


P.S: something like this is what I mean
http://australia.radicalsportscars.com/ ... 847f81.jpg

[PlatinumZealot]

Yes the kingpin angle will change as well from the front view.

Note that you can have a slanted king pin angle from the front view and sill have zero camber.

[peaty]

Yes the kingpin angle will change as well from the front view.

Note that you can have a slanted king pin angle from the front view and sill have zero camber.

Thanks! so what if you wanna change just camber, is that possible!?

[Facts Only]

Kpi (kingpin inclination) is the angle between the kingpin and the line through the upper and lower pivot point on the upright. Changing camber does not change the KPI.
This is what people are generally talking about when discussing kingpin angles.

[peaty]

Kpi (kingpin inclination) is the angle between the kingpin and the line through the upper and lower pivot point on the upright. Changing camber does not change the KPI.
This is what people are generally talking about when discussing kingpin angles.

so...is it the angle between the kingpin and the line through the upper and lower pivot point on the upright or between the true vertical and the line through the upper and lower pivot point on the upright!? I'm even more confused now

[Greg Locock]

FactsOnly - um, no. KPI is the angle between vertical and the steering axis in front view, typically the line joining upper and lower ball joints on the spindle. If you alter camber by shortening the upper arm, or spacing the inner arm bracket in or out, you will change both camber and KPI.

If you want to adjust camber but not KPI then you basically need a new spindle, or I suppose you could space the outer ball joints.

The reason that adjusting both at once is no biggy is that the changes in camber are probably of the order of a degree, and KPI changes of a degree do not make much difference. Note that you'll also be changing the scrub radius at the same time. Probably no big deal on a RWD race car.

[peaty]

FactsOnly - um, no. KPI is the angle between vertical and the steering axis in front view, typically the line joining upper and lower ball joints on the spindle. If you alter camber by shortening the upper arm, or spacing the inner arm bracket in or out, you will change both camber and KPI.

If you want to adjust camber but not KPI then you basically need a new spindle, or I suppose you could space the outer ball joints.

The reason that adjusting both at once is no biggy is that the changes in camber are probably of the order of a degree, and KPI changes of a degree do not make much difference. Note that you'll also be changing the scrub radius at the same time. Probably no big deal on a RWD race car.

Thanks! This explanation seems a bit more logical to me. That lead me to another question, lets say I have to make a calculation and I need the scrub radius or kinpin. Shall I use the theorical values or the installed and set with proper camber angle ones? Once again, the second one seems more logical to me...
Another thing, how could you space the outer ball joints and not change kingpin!? if you do such a thing the balljoint will change it's initial position or you won't change camber at all, isn't it!? As I see it, once again you're changing the length of the upper arm (at least in the radical ).
And last but not least, how does the spindle/suspension array that allow for just camber change looks like!? and how do you change camber without changing kingpin!?

thanks guys and sorry for so many stupid questions

[Greg Locock]

by spacing the OBJs I meant put a spacer between them and the spindle. That alters camber (and scrub radius) but not KPI.

[Tim.Wright]

Like Greg says, if you put the camber adjustment outboard of the upper and lower ball joints then the camber can be adjusted independent of the KPI.

Typically this is done by using shims between the upright body and the ball joint clevis like these implementations:




This way your kinematics remain untouched because all the joints stay in the same position.

If you do the camber adjustment by adjusting the inboard or outboard joints on the control arm you change not only the camber and kpi but also the camber gain, scrub radius, motion ratio and roll centre height as well the rate at which all of these things move with wheel travel. In my opinion its a pretty crappy way to change the camber on a race car (albeit a very commonly used method).

[PlatinumZealot]

To me the kingpin angle is just a name... It became less important to me. In the end I ended up adjusting everything around the camber angle, camber angle change with bump & steer and the caster and the scrub radius. King pin was adjusted to fit these three.

This was my attempt at suspension design.. A very basic attempt. I had no knowledge of tyre characteristics or anything like that.. but it was a nice lesson in the kinematics of a suspension. I ended up using the roll centre and camber specs from a lotus!

http://www.f1technical.net/forum/viewto ... =14&t=7716

[peaty]

Thank you very much to all of you! I've learn more reading here for a while than reading some books! Now everything is a bit more clear!
Thanks for the pictures Tim.Wright, now I can understand what Greg Locock meant to say. Now is time to learn about the relationship between all this parameters.

the camber and kpi but also the camber gain, scrub radius, motion ratio and roll centre height as well the rate at which all of these things move with wheel travel

Now that you mentioned it, I'm staring to see why it affect all those things

By the way, anybody knows where can I find a good read about camber compensation!?

[Tim.Wright]

Tune to win by Carrol Smith is a good primer on a lot of setup stuff without going into a lot of technical detail.

[peaty]

Tune to win by Carrol Smith is a good primer on a lot of setup stuff without going into a lot of technical detail.

thanks! I'll try to get a copy!

[Facts Only]

FactsOnly - um, no. KPI is the angle between vertical and the steering axis in front view, typically the line joining upper and lower ball joints on the spindle. If you alter camber by shortening the upper arm, or spacing the inner arm bracket in or out, you will change both camber and KPI.

If you want to adjust camber but not KPI then you basically need a new spindle, or I suppose you could space the outer ball joints.

The reason that adjusting both at once is no biggy is that the changes in camber are probably of the order of a degree, and KPI changes of a degree do not make much difference. Note that you'll also be changing the scrub radius at the same time. Probably no big deal on a RWD race car.

Well that's what I was saying, exactly that. But thanks for the down vote for me not wording it quite as well.

[peaty]

FactsOnly - um, no. KPI is the angle between vertical and the steering axis in front view, typically the line joining upper and lower ball joints on the spindle. If you alter camber by shortening the upper arm, or spacing the inner arm bracket in or out, you will change both camber and KPI.

If you want to adjust camber but not KPI then you basically need a new spindle, or I suppose you could space the outer ball joints.

The reason that adjusting both at once is no biggy is that the changes in camber are probably of the order of a degree, and KPI changes of a degree do not make much difference. Note that you'll also be changing the scrub radius at the same time. Probably no big deal on a RWD race car.

Forgot to ask you, why is not a big deal on a RWD race car!?