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4 The validated flange climb criteria are stated in Chapter 2 Wheel slide and wheel flats are an issue for almost every of this report with examples of applications in simulation and system, especially during the fall season. Although sev- track test for evaluating flange climb derailment. eral technologies have been applied to lessen the prob- In Phase II, the guidelines for applying to management and lem, more effective ones are needed. maintenance of wheel/rail profiles for transit operations were Noise related to wheels and rails generally are caused by recommended based on the problems and concerns uncov- wheel screech/squeal, wheel impact, and rail corruga- ered in the survey and current transit operations practices. tions. Lubrication and optimizing wheel/rail contact Chapter 3 presents these guidelines. would help to mitigate these problems. Chapter 4 is a glossary provided to help the reader better Friction management is a field that needs to be further understand the technical terms used in this report relating to explored. Application of lubrication is very limited in the flange climb criteria and the wheel/rail profile. transit due to the complications related to wheel slide and wheel flats. Reduction of wheel/rail wear can be achieved by opti- 1.3 SUMMARY OF PHASE I WORK mization of wheel/rail profiles, properly designed truck primary suspension, improvement of track mainte- Onsite surveys were conducted at six representative tran- nance, and application of lubrication. sit systems to investigate current practices and concerns Without a wheel/rail profile measurement and docu- related to wheel/rail profiles in transit operations. After com- mentation program, transit operators will have difficulty piling the information received and analyzing wheel and rail reaching a high level of effectiveness and efficiency in profiles that were collected onsite, common problems and wheel/rail operation and maintenance. concerns related to wheel/rail profiles and wheel/rail interac- Further improvement of transit system personnel under- tion were identified. These are summarized below: standing of wheel/rail profiles and interaction should be one of the strategic steps in system improvement. With Adoption of low wheel flange angles can increase the better understanding of the basic concepts, vehicle/track risk of flange climb derailment. High flange angles operation and maintenance would be performed more above 72 degrees are strongly recommended to improve effectively. operational safety. Rough surfaces from wheel truing can increase the risk Appendix A provides further information about the above of flange climb derailment. Smoothing the surface after issues. wheel truing and lubrication could mitigate the problem An investigation of wheel flange climb derailment criteria considerably. as applied to transit operation was conducted by extensive Introduction of new wheel and rail profiles needs to be computer simulations using the wheel/rail profiles collected carefully programmed for both wheel truing and rail from several transit systems. Based on simulations of single grinding to achieve a smooth transition from old wheelsets, preliminary lateral-to-vertical (L/V) ratio and wheel/rail profiles to new profiles. climb-distance criteria for transit vehicle wheelsets were pro- Independently rotating wheels can produce higher lat- posed. The proposed criteria were further validated through eral forces and higher wheel/rail wear on curves with- simulation of three types of transit vehicles. This research out adequate control mechanisms. has been based on the methods previously used by the Cylindrical wheels may reduce the risk of vehicle hunt- research team to develop flange climb derailment criteria for ing (lateral instability), but can have poor steering per- the North American freight railroads. The main conclusions formance on curves. drawn from this study are summarized below: Some wheel and rail profile combinations used in tran- sit operations were not systematically evaluated to The single wheel L/V ratio required for flange climb ensure that they have good performance on both tan- derailment is determined by the wheel maximum flange gent track and curves under given vehicle and track angle, friction coefficient, and wheelset AOA. conditions. The L/V ratio required for flange climb converges to Severe two-point contact has been observed on the Nadal's value for AOA greater than 10 milliradians designed wheel/rail profile combinations at several tran- (mrad). For lower wheelset AOA, the wheel L/V ratio sit operations. This type of contact tends to produce necessary for flange climb becomes progressively poor steering on curves resulting in higher lateral force higher than Nadal's value. and higher rate of wheel/rail wear. The distance required for flange climb derailment is Track gage and restraining rails need to be carefully set determined by the L/V ratio, wheel maximum flange on curves to allow sufficient usage of rolling radius dif- angle, wheel flange length, and wheelset AOA. ference (RRD) generated and to mitigate high rail wear The flange-climb distance converges to a limiting value and lateral force. at higher AOA and higher L/V ratios. This limiting

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5 value strongly correlates with wheel flange length. The The lower the friction coefficient, the higher the single longer the flange length, the longer the climb distance. wheel L/V ratio required. For lower wheelset AOA, when the L/V ratio is high For conventional solid wheelsets, a low, nonflanging enough for the wheel to climb, the wheel-climb dis- wheel friction coefficient has a tendency to cause flange tance for derailment becomes progressively longer than climb at a lower flanging wheel L/V ratio. Flange climb the proposed flange-climb-distance limit. The wheel- occurs over a shorter distance for the same flanging climb distance at lower wheelset AOA is mainly deter- wheel L/V ratio. mined by the maximum flange angle and L/V ratio. For independently rotating wheelsets, the effect of non- Besides the flange contact angle, flange length also flanging wheel friction coefficient is negligible because plays an important role in preventing derailment. The the longitudinal creep force vanishes. climb distance can be increased through use of higher Increasing vehicle speed increases the distance to climb. wheel maximum flange angles and longer flange length. The flanging wheel friction coefficient significantly The Phase I report detailing this study of flange climb cri- affects the wheel L/V ratio required for flange climb. teria is given in Appendix B.