Lateral stability analysis of a railway truck on roller rig

The development of experimental facilities for rail vehicle testing is bein g complemented by analytic studies. The purpose of this effort has been to gain insight into the dynamics of rail vehicles in order to guide developme nt of the roller rigs and to establish an analytic framework for the design and interpretation of tests to be conducted on roller rigs. The work descr ibed here represents initial efforts towards meeting these objectives. Generic linear models were developed for a freight car (with a characterist ic North American three-piece truck) on tangent track. The models were deve loped using the generalized multi body dynamics software MEDYNA. Prediction s were made of the theoretical linear model hunting (lateral stability) cha racteristics of the freight car, i.e., the critical speeds and frequencies, for five different configurations: (a) freight car on track, (b) the freig ht car's front truck on the roller stand and its rear truck on track, (c) f reight car on the roller rig, (d) a single truck on track, and (e) single t ruck on the roller stand. These were compared with the Association of Ameri can Railroads (AAR) field test data for an 80-t hopper car equipped with A- 3 ride control trucks. Agreement was reached among all the analytical model s, with all models indicating a range of hunting speeds of 2% from the high est to lowest. The largest discrepancy, approximately 6%, was indicated bet ween the models and the field test data. Parametric study results using linear model of freight truck on the roller rig show that: (a) increasing roller radius increases critical speed, (b) i ncreasing the wheel initial cone angle will decrease the hunting speed, (c) increasing the roller cant increases hunting speed, (d) decrowning of the wheelset on the rollers will not effect the hunting speed but induces longi tudinal destabilizing horizontal forces at the contact, and (e) lozenging o f wheelset on the rollers induces a yaw moment and the hunting speed decrea ses with increasing wheelset yaw angle. (C) 2001 Elsevier Science Ltd. All rights reserved.