MODIFICATION OF A HEAVY VEHICLE SUSPENSION TO REDUCE ROAD DAMAGE

A test rig for measuring the quasi-static performance of tandem suspensions in the laboratory is described. Measurements on a standard tandem leaf-spring suspension show it to have high effective stiffness in bounce and poor static load equalization. A method for eliminating the spring-end friction is investigated, and found to improve the performance significantly. A two-dimensional articulated vehicle simulation is validated with measurements from a test vehicle. The simulation is then used to study the effect on dynamic tyre forces of three modifications to the trailer suspension: softer springs; elimination of spring-end friction; and hydraulic dampers. The r.m.s. dynamic loads generated by the trailer axles are predicted to decrease by approximately 31 per cent and the theoretical road damage is predicted to decrease by about 13 per cent. The trailer suspension of the test vehicle is adapted to incorporate the three modifications and the measured reductions in dynamic tyre forces are found to be about half those predicted by the simulation.