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

Profile

• What was needed: iglidur plain bearings
• Requirements: Lightweight components that are particularly reliable, maintenance-free and economical in racing operation
• Industry: Automotive, racing
• Success for the customer: iglidur plain bearings with low friction properties are used at various points in the steering system, which reliably withstand extra-axial forces and thrust pressure; The use of spacers further reduced the wear on the slide bearings

Problem

In the Formula SAE competition, which hosts universities from around the world, technical racing solutions are built to compete against each other. Formula Seven, a small company made up of former members of one of the competition's teams, markets the most successful and effective technical solutions presented at the competition.
One of the technical solutions that emerged from the competition was a single-seater prototype racing car's steering gear with screw pinion and rack. Within the framework of Formula SAE, there were several specifications that were essential to meet when creating the component. First, to allow better vehicle dynamics, the entire steering system had to be very light so as to keep the overall weight of the racing car as low as possible. The materials must be reliable; they must enable the racing car to run safely and correctly over the long term even while being subjected to the high stresses of racing. It is especially important that minimal maintenance is required. Finally, an economical solution had to be found, hence the focus on using standard components.

Solution

The specifications in the racing car steering gear are met at various points by iglidur plain bearings. They are used in such applications as aligning the rack and allowing axial sliding with less rotation.
Particular attention was paid to dimensioning the seat and machining the shaft, to ensure locking friction is sufficient to prevent the seat from breaking away. The bearings must 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 shear pressure generated between the rack and pinion. Figure 2 shows two more bearings that house the pinion: In this case, flanged bearings are used (coloured magenta here) to allow the pinion to rotate. The washers, coloured green here, are also useful; they are used as a spacer to prevent wear to the two magenta bearings that would otherwise come into contact with the sharp edges of the teeth.

Cross Section Drawing 1

Cross Section Drawing 2