Stability and Curving Performance of Conventional and Advanced Rail Transit Vehicles

Analytical studies are presented which compare the curving performance and speed capability of conventional rail transit trucks with self steering (cross-braced) and forced steering (linkages between carbody and wheelsets) radial trucks. Truck curving performance is measured in terms of the work performed by the wheel/rail friction forces in the contact zone during curve negotiation. The contact work is used as an indication of wheel and rail wear rates as well as the additional power required to negotiate curves. Truck speed capability is expressed in terms of the maximum operating speed before lateral instability or hunting occurs. The studies are based upon a generalized computational model which is capable of representing conventional and innovative trucks that are currently being considered for implementation. the stability analysis utilizes a linear model while the curving analysis includes the essential nonlinearities associated with wheel/rail profile geometry, wheel/rail friction force saturation and suspension stiffnesses. In addition, the curving analysis includes an accurate description of two-point wheel/rail contact which can occur with common wheel profiles during flanging. Results of the study indicate that for curves greater than 5 deg, forced steering trucks can offer substantial performance improvements in comparison to well designed conventional trucks in terms of work performed during curve negotiation. Also comparison of a new AAR 1/20 wheel profile with a modified Heumann (single point contact) profile indicates that the latter profile can offer substantial performance improvements in terms of reduced work during curve negotiation.