Optimisation of primary suspension characteristics for heavy haul locomotives

An improvement of the tractive effort of heavy haul locomotives can be achieved by means of equalisation of weight loads between wheelsets to suit adhesion conditions. This solution, however, is not a perfect one because adhesion limit variability can lead to the overloading of wheelsets with poor adhesion conditions and not enough loading on the wheelsets with better adhesion conditions. The mechanical design of the primary suspension has a big influence on all these factors under both traction and braking operating modes. For example, increasing primary suspension stiffness can lead to decreasing the weight utilisation of the leading wheelset of each bogie. In addition, the yaw stiffness of the primary suspension can be considered as an important parameter for the radial steering process of wheelsets. The combination of these various parameters presents a problem which requires finding a balanced outcome between weight loading, stiffness and steering ability in order to provide an optimal performance. During the locomotive movement process in traction or braking modes, the weight of a locomotive body is distributed between bogies in different proportions which depend on many factors. The recent research performed as part of the R3-Engineering and Safety Program funded by the CRC for Rail Innovation shows a big influence of the primary suspension characteristics on the dispatched adhesion. The investigation on the influence of operational factors on axle weight distribution for heavy haul locomotives by the authors in Ukraine confirms the significance of such a theme. In this paper, the design of a locomotive with three-axle bogies (Co-Co) with variations of the primary suspension design characteristics has been studied by means of numerical experiments using the Gensys multibody software package. Primary suspension design for heavy haul locomotives is investigated, discussed and recommendations presented. Achieving optimisation in the primary suspension design should provide additional benefits to railway operators such as reduced rail and wheel wear, rail damage, wheel burns, etc.