Lightweight and maintenance-free plain bearings in steering system of racing car prototype

In the Formula SAE competition, in which universities all over the world take part, technical racing solutions are built to compete against each other. Formula Seven, a small company made up of former members of a team in the competition, commercialises the most successful and effective technical solutions presented in this competition.
One of the technical solutions that emerged from the competition was a steering gear with a helical pinion and gear rack for a single-seater racing car prototype. As part of the Formula SAE, there were several requirements that had to be met when creating the component. Firstly, the entire steering system had to be particularly lightweight in order to keep the overall weight of the racing car as low as possible and thus allow the vehicle to be more dynamic. The materials had to be particularly reliable, i.e. they had to enable the race car to drive safely and correctly over the long term while at the same time being exposed to the high stresses of racing. It is particularly important that as little maintenance work as possible is required. And finally, an economical solution had to be found, which is why the concept focussed on the use of standard components.

The specifications in the steering gear for the racing car are fulfilled by iglidur ® bearings at various points. They are used, for example, for the correct alignment of the gear rack and enable axial sliding with less rotation.
Particular attention was paid to the dimensioning of the seat and the machining of the shaft, as sufficient locking friction must be ensured to prevent the seat from breaking out. The bushings had to be carefully calibrated and surface-treated to avoid sliding friction and prevent seizure. The outermost yellow pair (Fig. 1) must absorb the off-axis forces transmitted by the forks connected to the steering rods, while the innermost blue pair must withstand the thrust pressure generated between the gear rack and pinion. Figure 2 shows two further bushes in which the pinion is housed: In this case, flange bushes are used (coloured magenta here), which allow the pinion to rotate. Also useful are the washers, coloured green here, which are used as spacers to prevent wear of the two magenta-coloured bushes, which would otherwise come into contact with the sharp edges of the teeth.