Technical Reports

Evaluation of Rail Rollover Derailment Study

  • 01
  • May
  • 1993
AUTHOR: Stephen E. Mace
KEYWORDS: Gage widening behavior; 125-ton gondola cars & locomotives; Angle of attack; Truck Warp
ABSTRACT: Research conducted by the Association of American Railroads at the U.S. Department of Transportation, Transportation Test Center, Pueblo, Colorado, led to an understanding of the gage widening behavior exhibited by several 125-ton gondola cars and locomotives in a 6-degree curve of the Facility for Accelerated Service Testing (FAST), High Tonnage Loop (HTL). For the gondola cars, the cause of the gage widening was attributed to truck warp, a condition in which the side frames of a truck rotate relative to the bolster and both wheel sets develop large angles of attack. The truck frames were found to warp due to a combination of poor wheel/rail contact geometry, insufficient wheel tread taper, and rail lubrication applied to only the gage face of the high rail in the curve. The gage widening attributed to the locomotives was found to be a consequence of unbalanced traction forces applied to the high and low rails in the curve resulting from differential rail lubrication. A unique two-phase approach was used to study the gage widening behavior, which consisted of actual track tests conducted on the HTL coupled with NUCARS simulations of the gondola cars. The gage widening behavior was first observed in 1991 during operation of the FAST Heavy Axle Load (HAL) consist on the HTL. Concern over excessive gage widening prompted the Federal Railroad Administration to sponsor research aimed at understanding this behavior and assure the continued safe operation of the HAL train.