ACKERMANN’S STEERING GEOMETRY

TKART Staff

27 June 2017

Kart steering is far more complex than a simple system for turning the front wheels on a bend. Its operation uses the Ackermann system: a revolutionary solution invented and patented in 1817 to optimise the direction of the front tyres and, consequently, driving around a bend

WHAT IS IT?

HOW DOES IT WORK?

IN PRACTICE

The starting point for explaining the Ackermann steering geometry is obvious: while on a bend, the outer front wheel has a wider trajectory (that is, a wider curve) than the inner wheel (which has a narrower curve). It should also be considered that a turning kart must have a rotation centre around which to do so, and around which the front wheels can rotate.
That being so, it is evident that if the front wheels are perfectly parallel during the bend, no rotation centre would be created because the axles of the wheels would remain parallel and without a common rotation point (which would be obtained from the intersection of the two axles of the wheels). In this way, the front wheels would slide, generating friction between tread and asphalt, tyre wear and loss of performance.

Ackermann’s steering geometry serves to offset the different direction covered by the front wheels along the curved trajectory to avoid this happening.
How? By causing the front wheels to rotate in a non-linear direction when turning the steering wheel. In doing so, a theoretical point is created (“theoretical” because, with the slipping of a 4-wheeled kart, the point actually varies) in which the 2 axes of the front wheels and the axis of the rear axle intersect.
Because, among other things, because of the caster angle, the bend geometry of a kart’s steering will lower the inner front wheel and lift the outer front wheel, with the transfer of much of the load to the front. The grip on the front is accentuated and the wheel travel direction is even more decisive.

ACKERMANN’S STEERING GEOMETRY ALLOWS YOU TO HAVE A THEORETICAL COMMON ROTATION CENTRE FOR THE BACK AND FRONT WHEELS

Steering rods, stub axles and steering columns: these are the elements that determine Ackermann’s steering geometry