EFFECTS OF WHEEL-RAIL CONTACT GEOMETRY ON WHEEL SET STEERING FORCES

Adverse wheel-rail contact geometry and flange lubrication have been i mplicated in a number of recent gage widening and rail rollover derail ments. The underlying derailment mechanism is shown to be a loss of wh eel set steering due to a reduction in wheel set rolling radius differ ence, 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. st rong two-point contact between hanging wheels and rails; 2. hollow wor n wheel treads; 3. heavy gage corner grinding on the rail; 4. high rai l gage face lubrication; 5. dry railheads. Studies conducted at severa l gage widening and rail rollover derailment sites have shown that the se conditions are not uncommon on North American railroads.