caster camber scrub ackerman rake trail

[LEE1969GB]

I want to know and understand what all of these do and mean, I will put what I know or think I know and please feel free to correct me and add to it or explain what it does.

Caster.
Draw a line through the top and bottom ball joints (or king pin) and it should incline bottom towards the front of the vehicle and top towards the rear of the vehicle, I think I have seen 12degrees? this gives steering self centering and am I correct to say helps with stability?

Camber.
Draw a line through the top and bottom ball joints and the top should be closer to the center of the car than the bottom, to keep the tyre flat on the ground of give positive or negertive camber for a particular set up. Is positive camber top of wheel in bottom out or the other way around?

scrub radius.
where a line through the top and bottom ball joints meets the ground within the tyre width, Do you aim for about the center of the tyre? stops the wheel being ripped out of your hands when you hit a big bump with one wheel.

ackerman,
This is set up by drawind a line through the center of the rear axle through a line between the top and bottom ball joints at the point where the track rod is to go, This makes the inside wheel turn more than the outside wheel.
Rake,/ trail
Not sure, I know on a motorbike its to do with the difference between the holes for the forks and the steering stem in the yokes but not sure how it works on a car.

What do you call the angle of the top and bottom ball joints, fixed to the hub?

[Bugpac]

You pretty much got it, from the videos you have posted of the pilot, and the riding conditions, i would say no more than 6 degrees caster, and no more than 5 or so camber change...

imagine looking at the car from the side, and taking and bending the chassis to wards the ground right behind the a arm mounts, Now you got rake...If you were going to rake it, I would only rake your style of car a few degrees...

[LEE1969GB]

Originally Posted by Bugpac

You pretty much got it, from the videos you have posted of the pilot, and the riding conditions, i would say no more than 6 degrees caster, and no more than 5 or so camber change...

imagine looking at the car from the side, and taking and bending the chassis to wards the ground right behind the a arm mounts, Now you got rake...If you were going to rake it, I would only rake your style of car a few degrees...

So if I put a lot of rake on that would make the front end dive when breaking?
Bug dont forget the heims.

[nutz4sand]

Originally Posted by LEE1969GB

Caster.
Draw a line through the top and bottom ball joints (or king pin) and it should incline bottom towards the front of the vehicle and top towards the rear of the vehicle, I think I have seen 12degrees? this gives steering self centering and am I correct to say helps with stability?

Yup with the king pin leaning backwards it tends to give stability and its called POSitive castor. Think Chopper motorbike LOTS or caster great stability. Turning suffers. Dirt bike favors less POS caster for more turning.

Originally Posted by LEE1969GB

Camber.
Draw a line through the top and bottom ball joints and the top should be closer to the center of the car than the bottom, to keep the tyre flat on the ground of give positive or negertive camber for a particular set up. Is positive camber top of wheel in bottom out or the other way around??

With the tire leaning inward at the top toward the car is called NEGative camber.

Originally Posted by LEE1969GB

What do you call the angle of the top and bottom ball joints, fixed to the hub?

I believe this is called the Kin Pin Inclination as the spindle is built with it in and that determines where the ball joints are in relation to how the spindle holds your tire. If I am wrong I wish to be corrected so I am right myself! Thanx! Bill

[Bugpac]

Originally Posted by LEE1969GB

So if I put a lot of rake on that would make the front end dive when breaking?
Bug dont forget the heims.

Ill get after it... what are you 12hrs time diff? so its like 1 am monday there now?

[Bugpac]

Ah i got it, never mind, its like 6:40 pm right...so i got a few hours...

[bdkw1]

Originally Posted by LEE1969GB

So if I put a lot of rake on that would make the front end dive when breaking?

Yes.

[LEE1969GB]

I believe this is called the Kin Pin Inclination as the spindle is built with it in and that determines where the ball joints are in relation to how the spindle holds your tire. If I am wrong I wish to be corrected so I am right myself! Thanx! Bill[/quote]

How does King pin inclination affect the handling, I assume the wheel will lean more on full lock? I noticed when I first saw protodies buggy it seems to have a lot of KPI shell we call it (takes me forever to type)

[nutz4sand]

I know having to much or too little KPI affects feedback to the steering system and the buggy in genral. It affects the feel the tires impart to the driver.

It also effects the tires scrub radius due to this. As you turn the steering the tire is forced to pivot around the KPI axis. To much or to little makes the scrub worse. Some people want the pivot right under the tires contact patch. Others want it in some and other like it outside the tires contact patch.

I am tired and cannot think at this moment but someone who knows may be able to tell what the differances will do to the steering effects. I was thinking of making a few elcheapo spindles with different angles to drive around slow with to see what I liked before I made nice ones. Bill

[bdkw1]

The closer you can get the lower ball joint to the center of the tire and the less KPI you can run to get the proper scrub the better off you will be.