Dynamic effect of the bump steer in a wheeled tractor

The steering system of a compact wheeled tractor is analyzed using a commercial multi-body simulation software. The effect of axle-oscillation induced steering errors and of the axle impacting the bump stops attached to the tractor body is compared for two design variants. It is shown that by diminishing the kinematic cross-coupling between the steering-control linkage and the axle oscillation, a favorable reduction of the dynamic loads in the steering mechanism components can be obtained for normal operation conditions of the vehicle. However, if the axle impacts violently its bump stops, the reaction forces in the joints can be much higher; contrary to one’s intuition, these forces are larger for steering systems with reduced or no bump steer. Based on these conclusions, several design recommendations to the partitioning engineer are advanced at the end of the paper.