Ackerman, Toe and a Few Other Random Thoughts«
The diagram below outlines the important geometry in determining the motions of the steer wheels in a vehicle that uses Ackerman steering geometry. Ackerman is aninteresting problem because it is dynamic. That is to say that we have two componentsmoving together ± the left and right steering knuckles, but the relationship between their motions changes as we move them. This is a real head scratcher. It¶s a bit like having a bowling ball in a dark room and throwing other bowling balls in an attempt to locate it bylistening for an impact. Every time you find the ball by crashing into it, it moves andagain don¶t know where it is.Luckily we have some mathematical voodoo that can help us figure it out. Let¶slook at the important distances and angles. The two most fundamental distances are thewheel base of the car and the kingpin center to center distance. If we draw two linesrepresenting the wheelbase and the distance from the car¶s center line to one of the king pins, we can make a triangle. By design, the line that goes through the centers of theAckerman arm forms the hypotenuse of this triangle. See below.R
Wheel Base
K i n g P i n C e n t e r t o C e n t e r D i s t a n c e
T i e R o d L e n g t h
K i n g P i n C e n t e r t o C e n t e r D i s t a n c e 2