Technical Reports

Torsional Stiffness of Railroad Coupler Connections

  • 01
  • Nov
  • 2010
AUTHOR: Robert Trent, Anand Prabhakaran, and Vinaya Sharma
SUBJECT: Freight Operations, Hazardous Materials
KEYWORDS: coupler torque; coupler stiffness; rollover; shelf coupler; tank car; tank car safety
ABSTRACT: Tank cars are required to use double shelf couplers to prevent the coupler of an adjacent car from puncturing the tank head in the case of overrides or accidents. However, the added torsional stiffness of such coupler connections might lead to tank cars „taking down‟ adjacent coupled cars in rollover derailments. This project investigated the torsional behavior of freight car coupler connections through analysis and test. Tests included the following coupler combinations: no-shelf to no-shelf, shelf to no-shelf, and shelf to shelf combinations in both clockwise to counterclockwise directions. Coupler specimens of each test run were mounted in a test fixture with one coupler receiving a torque application. Results show a greater torsional stiffness for coupler connections that have couplers with the shelf feature over those that do not. The more shelves that are present in a coupler connection, the greater the transmission of torque, implying that the presence of a shelf coupler or couplers adds to the torsional stiffness of the coupler connection. What is still not clear is whether this stiffness will contribute to, or help prevent, rollovers of adjacent coupled cars. We recommend further study into the potential of stiff coupler connections for propagating car rollovers, specifically through the use of vehicle dynamics models that incorporate the effects car suspension and car structure, in addition to the stiffness of coupler connections.