Effective Friction Control for Optimization of High Speed Rail Operations

Expected growth of High Speed Rail (HSR) in North America will in many instances involve operation on existing infrastructure, shared with other traffic. This will pose many challenges, not least of which will be wheel and rail wear, and ride quality. This paper addresses how effective friction control can be employed to mitigate these factors and provide an important tool to the designers of new systems. Case studies describe successful use of train mounted solid stick LCF flange lubrication on high speed trains in East Asia and Japan. In each case, higher speed train operation has involved operation on areas of track with greater curvature than usual on dedicated high speed track. Appropriately designed LCF systems provide an inherently very high level of reliability and very low flange wear rates. Use of dry thin film lubricant technology has advantages over use of liquid lubricants (oil and grease) which can experience splash and fling off at high train speeds. Train mounted solid sticks provide greater consistency / reliability and ease of maintenance compared with wayside gauge face lubrication. Complementing practical field experience, modeling studies are presented which show the potential of high performance flange lubrication to allow for additional flexibility in designing wheel profiles for high speed rail. The ideal profile will balance vehicle stability (benefiting from lower conicity) and curving performance (benefiting from higher conicity). In a high speed train with long wheel base and high suspension stiffness operating in areas with significant curvature, finding an appropriate compromise becomes even more challenging than usual. Controlling flange wear at low rates with highly effective solid stick lubrication offers the opportunity to use wheel profiles providing lower effective conicity and therefore better ride quality, without compromising wheel life. This approach will be practical only in a scenario where a very high reliability wheel / rail lubrication system is employed.