Technology Digests / Modeling of Railcar Draft Systems

TD23-026

December 18, 2023
Authors
  • Adam Klopp
  • Alyson Sasaoka
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Key Findings

  • Drift simulations, combined with physical impact tests, were used to evaluate the overall energy management ability of different freight car draft systems, including the impact protection and slack control these systems provide.
  • Drift simulation results showed that, due to reduced slack control, blocks of cars with EOCC units experienced higher coupler forces, higher in-train speed differences, and lower carbody accelerations compared to blocks of cars with friction draft gears or hybrid draft systems.
  • Because they were better able to limit relative motions within the train, friction draft gears and hybrid draft systems generally provided better train action control, including lower coupler forces, lower in-train speed differences, and lower variability in these results.

Modeling of Railcar Draft Systems

As part of the Association of American Railroad (AAR) Strategic Research Initiatives (SRI) program, MxV Rail and the End-of-Car (EOC) Energy Management Task Force of the AAR’s Equipment Engineering Committee (EEC) are working together to develop a combined testing and modeling approach to evaluate draft system performance. This approach includes both physical impact testing, used to evaluate impact protection and characterize the systems, and modeling, used to evaluate in-train scenarios that are not necessarily covered by existing standards. Draft systems mitigate damage to railcars and lading by managing energy from coupler forces generated during train operations. In North America, most draft systems are either friction draft gears or hydraulic end-of-car cushioning (EOCC) units. Friction draft gears use a combination of spring elements (e.g., elastomeric and metal springs) and friction elements (e.g., friction clutches and wedges) to absorb energy from relative motion between cars and control slack, with a typical displacement…