Gauge face contact implications of bogie rotation friction in curving

QR National’s experience of wheel wear in the operation of its central Queensland coal fleet has shown a high sensitivity to the proportion of the wagon fleet with high bogie rotational resistance. In periods where significant parts of the fleet exhibited high centre bearing rotational resistance rail lubrication conditions also were deteriorated and wheel life fleet wide was noticed to shorten. QR National believe that this increase in wheel rail wear was the result of reduce rail lubrication effectiveness caused by unfavorable contact mechanics at the gauge face of the rail. The Rail CRC Australia Bogie Rotation Friction Management project has conducted a case study of the QR National VSA wagon. The case study analysis shows wheel rail wear on the Goonyella system operations of VSA wagons are very sensitive to bogie rotation friction especially for the tightest curve (304 m) where wheelsets 1, 2 and 3 all flange. The wheel rail contact mechanics are dependant on the bogie rotation friction specifically the angle of attack generated on axle 1 and 2 increases due to bogie rotation friction. The flange contact forces and resulting contact stresses change only slightly with increases of bogie rotation friction, under 10%. The significant change in the gauge face contact mechanics is the creepage angle. The creepage angle on the gauge face of the 304 m curve changes from 47 to 65 degrees to the rail axis for axle 1 and 18 to 57 degrees on axle 2. With this change in the flange contact creepage angle lubricant is increasingly swept off the rail gauge face increasing the friction coefficients for following wheelsets. Previous studies on bogie rotation friction has shown that wear losses from high bogie rotation forces are due to warp of the bogie. Bogie warp occurs in the track transition in order to rotate the bogie however in constant curving there is no need to retain the warped bogie shape and transition design can be used to relieve bogie warp1. An alternative curve transition design is suggested for the 304 m curve. This alternative design termed a “curvature overrun transition”, has small section of tighter curve radius in the transition section whilst the curve body is a slightly larger radius giving a minimal change to the curve alignment. The curvature over run design gives significant improvements to the angle of attack and contact mechanics in the curve body. However wheel wear savings only occur for vehicles having high bogie rotation friction and rail wear rates are effectively higher due to higher peak rail wear.