Based on dynamics theory of multi-body systems, a nonlinear mathematical model of
frame-bogies with Lenoir damper for freight cars is established. A tank car is taken as an example to
study the effects of main parameters on hunting stability, dynamic curving behaviors and running
responses of vehicle systems. It is shown that the dynamic behaviors of a freight vehicle can be
improved greatly by optimization and balancing of the parameters of the bogies. For the bogies
concerned, the critical hunting speed can be raised, without deteriorating the performances on
curved lines, by properly increasing the stiffness of the axle-box suspension and the friction torque of
side bearing, as well as reducing the longitudinal clearance of side bearings.