Objectives
The purpose of the steering system of a Supermileage vehicle is simple: reduce the friction of the wheels against the pavement, have a maximum of control over the handling of the vehicle and still manage to make the lightest vehicle possible. Also, the handling must respect a turning radius of minimum 6 meters and a small braking distance.
Framework
These objectives are achieved by optimizing the Ackermann angle, the camber, the caster, and the wheel alignment.
Figure 1: Wheel alignment
Figure 2: Caster
Figure 3: Camber
Figure 4: Ackermann angle
Obviously, the parallelism must be perfect to eliminate friction losses in the tires. Angles of caster and camber are more difficult to identify, it’s all about making compromises. A very simple method to determine the Ackermann angle is shown in the top of Figure 4 and the effect of this angle is shown in the bottom of Figure 4. Mass reduction is performed by carefully choosing the materials of each part and by optimizing its geometry. Carbon and aluminum are recommended.
Results
The selected system is composed of pivoting blocks made out of aluminum connected by a carbon bar to ensure parallelism.
Figure 5: Pivoting block
The wheels are attached to the blocks through the hubs and the blocks are fixed to the carbon structure of the hull by two freely rotating seals. As their name suggests, rotating blocks rotate with the wheels to allow the vehicle to turn. The rotational movement of the handlebar is transmitted via a universal joint to a pivot that transforms the movement in translation. The translation is made to the end of a pivot block with another carbon bar. The handlebar and the pivot are supported by a single piece of carbon ensuring the rigidity of the assembly.
Figure 6: Support of the handlebar and the pivot
Figure 7 shows an exploded view of the steering system while figure 8 shows the assembly of the steering system.
Figure 7: Exploded view of the steering system
Figure 8:Assembly of the steering system
The alignment system is mechanical for the front wheels and optical for the rear wheels.
