Problem:
The swing axle allows the wheel pressure to be evenly distributed on the road, regardless of lateral and longitudinal unevenness. The design engineers were looking for suitable plain bearings and thrust washers for the swing axle joints. Although the main load is absorbed by a hydraulic cylinder, the bearings in the longitudinal and transverse axles are exposed to high forces resulting from the tare weight of the semi-trailer and the load being transported.
In addition to the high load capacity, there are further challenges: unlike typical lorry trailers, semi-trailers with these swing axles are sometimes exposed to the weather for months on end. Regular lubrication would be difficult to manage given the large number of bearing points. The use of a centralised lubrication system would increase production costs, while manual lubrication of each individual joint would be extremely time-consuming and unattractive for the end customer. The originally envisaged solution of using bronze bearings did not fulfil the requirements package of high load capacity, weather resistance and minimal maintenance.