Interface - The Journal of Wheel/Rail Interaction

HIGH CANT DEFICIENCY

Operating at High Cant Deficiency (continued)

Figure 5 shows curving forces at 12 inches cant deficiency. Changes at the truck leading axles are minor, while trailing axle changes are dramatic. The trailing axle now takes an equal role in generating truck lateral forces. Gauge spreading no longer occurs at the trailing axle. Instead, the low rail wheel now acts to pull the low rail towards track center. The steering moment on the leading axle is largely unchanged, while the steering moment on the trailing axle has changed sign.

Figure 6 shows how truck lateral forces are affected by cant deficiency. At the leading axle, high rail lateral forces hardly change. The required increase in net axle lateral force at high cant deficiency is obtained by reducing forces at the low rail. These go from a larger negative value to a smaller negative value. There are also substantial increases in lateral force on the trailing axle. While it is typically assumed that high-speed curving causes significant high rail loads, it is actually the low rail forces that change most to create the net lateral load as the vehicle reacts to centrifugal force.

Wheelset angles of attack decrease with increased cant deficiency. The diagram at the top right of Figure 7 shows the usual curving orientation of a truck at balance speed. The leading axle takes an angle of attack and the trailing axle takes a near-radial position. The bottom right diagram shows the curving orientation at high cant deficiency. In this condition, the leading axle moves into a radial position (the angle of attack decreases) while the trailing axle goes to an over radial position. This has important consequences in terms of derailment safety.

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