Traction and curving behaviour of a railway bogie

Abstract

In conventional railway systems, vehicles exert traction and must also negotiate curves. The creep forces between a bogie and the track are shown here for a wide range of curve radii (300–1800 m), a wide range of applied traction (traction ratios of 0, 0.14 and 0.28) and for bogies of widely different yaw stiffness, which is the factor that most affects a bogie’s curving performance. Traction destroys the steering performance of any bogie, increasing the lateral displacement of the critical leading wheelset and also its angle of attack, thereby increasing the tendency for ‘squeal’ noise. The resultant wheel/rail creep forces also typically increase and change orientation significantly. There is a significant difference in creep force across both wheelsets, with slip occurring first at the leading wheel on the high rail. For modest levels of applied traction, low yaw stiffness improves curving performance. However, low yaw stiffness becomes ever less beneficial as traction increases. Indeed, at levels of applied traction typical of modern locomotives, a bogie and the wheelsets within it behave essentially as a rigid bogie, regardless of the yaw stiffness.