Technical Reports

Effect of Track Twist on Vehicle Dynamic Performance: Final Report

  • 01
  • Dec
  • 1998
AUTHOR: Huimin Wu
SUBJECT: Track/Train Interactions
KEYWORDS: Performance-Based Track Safety Limits, Transportation Technology Center, TTC
ABSTRACT: Results of tests conducted at the Transportation Technology Center (TTC), Pueblo, Colorado, indicate that vehicle response to track twist varies significantly with car type. Critical response variables include car body torsional stiffness, truck spacing, track alignment (tangent or curve), track geometry and wheel/rail friction coefficient. Test data collected during this project provides an experimental basis for investigation of performance-based track safety limits. Track twist is defined as a variation in cross level between two points along the track. Excessive twist can cause truck center plate unloading on tangent track as indicated by wheel unloading, or wheel climb on curved-track as indicated by high wheel or axle L/V ratios. The limiting wheel unloading and L/V ratio criteria specified by the industry for new car acceptance (90 percent reduction of static vertical wheel force, 1.0 single wheel L/V ratio and 1.5 axle sum L/V ratio) were used as the guideline limits for this test. Three vehicles were tested in an empty load condition — a 100-ton, 89-foot center beam flatcar, a 100-ton covered hopper car and a 70-ton tank car — over cross level and combined cross level/alignment perturbations on tangent, 7.5-degree curve, and 12-degree curve test zones.