Ackerman

[ShadowBolt]

I never really understood it but this article makes it a little easier.
I think I got it now. Enjoy.

http://autorepair.about.com/gi/dynam...principle.html

JJ

[edrock96GT]

Ah yes, I remember now.
Ackerman= toe out in turns.

When a car turns, it's rear axle is aligned with the pivot point of the turn, forcing the front wheels to follow two different arcs.

Here ya go:

[Hood]

Ah yes, I remember now.
Ackerman= toe out in turns.

Yes, sort of... it describes the dynamic toe change acquired by the different angles of the steering arms. By design it SHOULD produce the required toe-out (a lot of formula cars have adjustable ackerman for tuning).

When a car turns, it's rear axle is aligned with the pivot point of the turn, forcing the front wheels to follow two different arcs.
Here ya go:

Almost true... actually a line perpendicular to the center of the car close to half-way between the axle centerlines is aligned with the pivot point (center of the turning circle). This point varies with wheel-base (the reason it isn't exactly half-way is because the rear wheels aren't turning away from the circle, kinda like the GMC truck with 4-wheel steer). The rear axle centerline traces an arc somewhat aft of the pivot point. In the above sketch, if you drew a vehicle centerline perpendicular to the rear axle centerline, the front tires are nowhere near equidistant off the vehicle centerline.
So... yes, the front tires have to follow different radius arcs in order to be "scrub free" during their roll. And, actually, the rear tires do this as well but they are not on the same arcs as the front tires... they are following on shorter radius arcs.

my .02

[David Love AI27]

Ah yes, I remember now.
Ackerman= toe out in turns.

Yes, sort of... it describes the dynamic toe change acquired by the different angles of the steering arms. By design it SHOULD produce the required toe-out (a lot of formula cars have adjustable ackerman for tuning).

When a car turns, it's rear axle is aligned with the pivot point of the turn, forcing the front wheels to follow two different arcs.
Here ya go:

Almost true... actually a line perpendicular to the center of the car close to half-way between the axle centerlines is aligned with the pivot point (center of the turning circle). This point varies with wheel-base (the reason it isn't exactly half-way is because the rear wheels aren't turning away from the circle, kinda like the GMC truck with 4-wheel steer). The rear axle centerline traces an arc somewhat aft of the pivot point. In the above sketch, if you drew a vehicle centerline perpendicular to the rear axle centerline, the front tires are nowhere near equidistant off the vehicle centerline.
So... yes, the front tires have to follow different radius arcs in order to be "scrub free" during their roll. And, actually, the rear tires do this as well but they are not on the same arcs as the front tires... they are following on shorter radius arcs.

my .02

THE HELL YOU SAY!!??

[edrock96GT]

My mistake, I didn't mention that the rear wheels are following a shorter arc than the front (and my diagram doesn't show it)...whoops. :wink:

I was taught that the rear axle is on the pivot line though.

[AI#97]

If you are driving slow enough for the rear wheels to follow that pace, you ain't got a hair on your nuts.....YAW is what turns a car...especially a CMC car you pussies!!!!!

[David Love AI27]

If you are driving slow enough for the rear wheels to follow that pace, you ain't got a hair on your nuts.....YAW is what turns a car...especially a CMC car you pussies!!!!!

I do believe there was a CMC car at Nationals that consistantly had the rears OUTSIDE the arc... :P