Effects of wheel-rail contact geometry on wheel set steering forces

Abstract

Adverse wheel-rail contact geometry and flange lubrication have been implicated in a number of recent gage widening and rail rollover derailments. The underlying derailment mechanism is shown to be a loss of wheel set steering due to a reduction in wheel set rolling radius difference, leading to shear deformation of the truck and the generation of large lateral gage spreading forces. A series of theoretical analyses and field experiments have been conducted that demonstrate the loss of steering caused by the following wheel-rail contact conditions: 1. 1. strong two-point contact between flanging wheels and rails; 2. 2. hollow wom wheel treads; 3. 3. heavy gage corner grinding on the rail; 4. 4. high rail gage face lubrication; 5. 5. dry railheads. Studies conducted at several gage widening and rail rollover derailment sites have shown that these conditions are not uncommon on North American railroads.