Technology Digests / Modeling of Rail Welding Alignment and Finished Dimensional Tolerances

TD26-016

Date Posted: July 28, 2026
Authors
  • Ulrich Spangenberg
  • Jack Schultz
  • Ananyo Banerjee
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Key Findings

  • Varying the crown of the weld while holding all other variables constant in a NUCARS®* simulation led to a linear increase in the maximum vertical force between a loaded hopper car and the track. This trend was observed at speeds from 40 to 70 mph and with both normal and frozen track conditions.
  • It is recommended that the current requirement of 0.06-inch crown be maintained.
  • The current required tolerance of a 6-inch taper/0.01-inch vertical offsets (VOs) can reasonably be relaxed to a 4-inch taper/0.01-inch VO. Simulation results show that this change would have minimal effect on vertical forces.
  • Lowering taper length tolerances below 4 inches/0.01 inch of VO would likely result in an unwanted increase in vertical force.
  • NUCARS® is a registered trademark of MxV Rail.

Modeling of Rail Welding Alignment and Finished Dimensional Tolerances

Since the early 1990s, MxV Rail has been conducting various tests on thermite welding (TW) and electric flash butt welding (EFBW) processes as a part of the welding project funded by the Association of American Railroads (AAR) Strategic Research Initative (SRI) program. As part of this research, MxV Rail supports the American Railway Engineering and Maintenance-of-Way Association (AREMA) through testing and science-based modeling approaches to the recommended welding guidelines for railroad industry.1 Section 3.11, Chapter 4 of the AREMA Manual for Railway Engineering (MRE) provides specifications for the fabrication of continuously welded rail including post- weld alignment, finish grinding requirements, and alignment tolerances.1 The history of the existing tolerances for vertical offset, crown, taper length, and their allowable combinations when performing weld alignment and finish grinding is not clearly known. Current welding alignment practices and finish grinding practices vary across different railroads, and measurement accuracy varies based on operator skills.…