Ackermann steering
Why the inside wheel of a turning car points further round.
A car going round a corner has its wheels on circles of different radii, so they should be at different angles: the inside one turns further than the outside one. Steer both to the same angle and one of them has to scrub.
Ackermann's answer is a linkage: the steering arms are angled inwards so that they meet at the rear axle, and the geometry does the rest. It is a four bar linkage doing something very specific.
| Quantity | How it is worked out |
|---|---|
| The condition | cot(outer) − cot(inner) = track ÷ wheelbase |
| The construction | steering arms aimed at the middle of the rear axle |
The app's steering scene is a linkage, not a rule, so the angles come out of the geometry. Turn it lock to lock in blueprint view and read the two angles.
Open the ackermann scene in the app to watch this one run.