Axle Failures Induced by Incorrect Steering Geometry for a Four-Wheel Steer, Off-Highway Vehicle

Recent testing of a new rough terrain forklift, which has operator-selectable two-wheel and four-wheel steering modes, led to the discovery that incorrect steering geometry can cause significant wear and tear, and even failure, of an axle. The paper discusses the inherent incompatibility between two-wheel and four-wheel steering geometry. The specific tests which led to the current understanding of the failure mode are described. The test results are analyzed in the context of cornering forces generated by a tire operating at a slip angle. The implications of the conclusions for the design of four-wheel steer, off-highway axles and vehicles are discussed.