Idealized steering for hauling locomotives

Most of the passive and active steering developments of traction bogies have been directed towards high speed rail or light rail and commuter rail applications. Previous studies ignored coupler forces and often assumed the wheel rail profiles have ample conicity for the curving task. There is little work directed towards high adhesion rates which is a critical area for freight locomotive performance. In heavy haul train operations ruling grades are often associated with tight curvatures, and steering tasks of hauling locomotives are affected by lateral components of longitudinal train forces. Haul locomotives also have a significant yaw moment from coupler forces making uneven longitudinal creeps useful in balancing these yaw forces. The use of larger diameter wheels on locomotives reduces effective steering conicity such that contact profiles may become insufficient to negotiate tight curves. The large diameter wheels make longitudinal creepage or slip inevitable and Goodall et al. [ 1] definition of perfect steering unattainable. A new criteria for ideal steering in these conditions is proposed. For hauling locomotives, ideal steering is defined as when the lateral rail creep and contact loads of each axle in one bogie are equal and longitudinal creeps are positive to the applied traction. This definition is applicable to all curving tasks that a hauling locomotive encounters while still applying low wheel rail creep forces. In most of the cases ideal steering can be achieved with zero lateral creep forces. The paper describes equations for quasi-static curving forces including traction and in-train forces. An analysis of curving forces for locomotives with three axle bogies is made with the equations for various curvatures and with haulage locomotives in different train configurations including pusher configuration.