Interface - The Journal of Wheel/Rail Interaction

VEHICLE SUSPENSIONS

Improving Truck Designs to Reduce Forces Transmitted to Track

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The lighter overall weight and improving rolling resistance of these new truck designs have also been shown to reduce lateral and vertical forces. Consequently, they are expected to also reduce wheel and rail wear, and fuel consumption. The use of long-travel, constant-contact side bearings (required under the new the M-976 specification) will also help maintain high-speed stability.

Three car types—loaded and empty 4427 cubic-foot hoppers with 39- to 40-foot truck centers and an empty 6000 cubic-foot hopper, which poses challenges in curves and spirals—were tested for hunting, steady-state curving, curve resistance, spiral, twist and roll, pitch and bounce, yaw and sway, and dynamic curving. At present, four trucks have received preliminary approval for M-976:
• ASF Motion Control™ Truck System (Pennsy pads) see sidebar
• Standard Car Truck S2HD split wedge (Pennsy pads)
• Standard Car Truck S2ED single wedge (with Lord pads)
• Standard Car Truck S2E split wedge (with Lord pads)

The Standard Car Truck S2E split wedge (with Lord pads) has received limited approval under the S-286 specification for application to open-top coal cars having a center of gravity of 93 inches or less. This specification also requires these cars to undergo stress and fatigue analysis and to be fitted with improved suspension and brake components.

An important consideration in the development and implementation of the M-976 and S-286 specifications is that whenever maintenance is performed on these cars and truck systems, the components must be replaced in-kind to ensure that these performance levels are maintained. Over the long haul, these improved suspensions are expected to reduce vehicle and track maintenance, operating costs and the number of derailments, Berg said. "They are designed to mitigate the effects of increased axle loads and ultimately reduce the stress state of the rail system."

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