The dynamic stability of a simplified four-wheeled railway vehicle having profiled wheels

Abstract The dynamic instability of a four-wheeled railway vehicle, due to the combined action of the creep forces acting between the wheels and the rails and the conicity of the wheels, is investigated in the case where the vehicle body is attached to the wheels by means of an elastic suspension. The suspension is assumed to have negligible stiffness in the longitudinal direction, and the wheel treads are profiled instead of being purely conical. It is shown that there are two possible types of instability; the wheelset instability which occurs at high speeds and which involves mainly wheelset motion and the body instability which occurs at low speeds and involves large displacements of the body. The effect of the restoring force which arises from the lateral component of the variation of the normal reaction between wheel and rail with lateral displacement is shown to have an important effect on stability, and it is indicated how this effect can be exploited in conjunction with suspension damping in the proper design of a railway vehicle for stable running at high speeds.