This paper describes recent theoretical and experimental work carried out by CN Rail Research in an effort to improve the performance of conventional 100-ton freight car trucks through the use of nonstandard wheel tread profiles. The steady state curving behavior of a conventional three-piece frame truck has been studied using a nonlinear computer simulation to identify the effects of wheel conicity and track curvature on wheel-rail forces and on wear parameters. Lateral curving forces were compared from a field test using dynamometer tieplates on a 5-degree curve (350 m radius) for four different wheel profiles including the AAR standard for new wheels. Preliminary results of a long term test on cars in revenue service are presented to show the effect of initial wheel profile on the early wear patterns as well as to show the methodology used for comparing the profiles under test. Finally, a brief review is made of the potential benefits resulting from the use of wheel profiles which are better adapted to service-worn rail head contours.

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