What is steering Ackermann?

Edited: 6/17/2007 9:41:19 AM by BioMax

Ackerman is really hard to explain, but I'll try. And don't get your feeling hurt if you don't get it, I've tried to explain this to so many people and only a few understand...

On a straight axle front end (the one pictured in the Ackerman diagram) the tie rod is connected to both spindles. So the Ackerman would be figured just as it is in the diagram. But on an A-arm front end, the tie rods would be attached to the spindle (on the outside) and the centerlink (on the inside.) Because the centerlink can be moved foward or backward, Ackerman is effected.

The way to figure Ackerman for a spindle with a steering arm that doesn't folow the ackerman diagram, is to use the diagram to find the angle of the spindle/tierod relationship and figure it into diagram 2. The angle we are looking for is angle "Ref" The lines Re and ef meet and make that angle. Lets say that the angle is 80deg. If you take that angle and plug it into your spindle/balljoint relationship you will end up with something like what is shown in diagram 2. The center tierod points are moved back because the steering arm on the spindle is closer to the center of the vehicle. the angles Aew and Bfy are equal to Aef and Bfe. If it were a rear steer it would be the same for the involved angles. If the steering arm on the spindle was further out from the center (on a front steer) then the original diagram, then the center tierod points would be further foward in order to keep with our figured angle from the original ackerman diagram.

my brain hurts now

x2

hmmmmmm. interesting

hey max can you define the points? and are these diagrams looking from above?

Those are from directly over head. The top one, the front is to the right and the bottom one, the front is to the top.

Edited: 6/17/2007 3:17:04 PM by slammit

Max is this what your talking about?http://www.auto-ware.com/setup/ack_rac.htm http://www.rctek.com/handling/ackerman_steering_principle.html

I got most of what I need to set up that BSA frame. I'll probably call you a couple of weeks.

i had an engineer friend of mine explain that to me a few years ago and it only took me like 2 times of explaining to somewhat understand. LOL

basically its showing the relationship between suspension travel and camber/caster angles. a control arm front suspension has unequal length control arms, so it changes the camber angle throughout the travel. in doing so it also changes the angles on you tierods which causing toe angle changes. also, it is why when you turn your wheels to full lock, you notice the wheel that is ont he side you are turning to is actually turned farther than the one on the other side. but they both come back straight in the center

Originally posted by HarryBalls



Maybe im way off but in a dummies words....the position/degree of the spindle leaning back/forward in relation with the balljoint??? Also it has a major effect of how the vehicle turns and exits a turn??

No. That's caster. That isn't even related to ackerman. It is only adressed from an overhead view, caster is viewed fron a side view only. As for the effect it has on a vehicle turning, that's still a debate among racecar builders and designers. If you check out the links that slammit posted there isn't a whole lot of concern with tuning a vehicle's ackerman for handling. The reason that I posted this was to make aware that there is such a thing and that anti-ackerman is a bad thing. If you design your own front suspension or mount a rack into the wrong spot and create anti-ackerman, you will have a vehicle that drives like total shit!