Technology Digests / Assessment of Wheel Profiles and Switch Point Derailments

TD23-011

July 25, 2023
Authors
  • Ulrich Spangenberg
  • Matt Wenger
  • Arun Wickramasuriya
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Key Findings

  • At turnouts in good condition without a chipped or gapped switch blade, wheel profiles with undesirable traits such as a flange tip radius less than 5 mm do not present a substantial risk of derailment.
  • Wheels with a flange tip radius less than 5 mm (~0.2 in.) made up 6.8 percent of the studied wheel population.
  • Wheels with an acute flange tip radius and a dual flange angle made up 1 percent of the total population.
  • Worn wheels with an acute flange tip radius and a steep flange angle ran with a lateral offset from the center of the track and a significant angle of attack.

Assessment of Wheel Profiles and Switch Point Derailments

Worn wheels with a steep flange angle accompanied by acute flange tip metal flow have been associated with derailments at switches.1 As part of the Association of American Railroads’ (AAR) Wheel/Rail Profile Design and Maintenance Strategic Research Initiatives project, MxV Rail investigated the interaction between worn wheels and a turnout switch point to research the likelihood of derailment at the switch point. Several worn wheel profiles were identified and studied by means of NUCARSâ* simulations to determine the wheels’ dynamic behavior when approaching a switch point. The simulation results were used in concert with three-dimensional (3D) models of the worn wheels and a measured switch point to discuss the likelihood of a derailment.  INTRODUCTION  Turnouts rely on complex track geometry that includes complex rail profiles and movable parts to safely guide trains from a track to an adjacent track. Due to the reliance on complex track and rail geometry that…