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OCR for page 19
19 R=100 ft R=250 ft 1.8 R=320 ft R=500 ft 1.6 R=755 ft R=955 ft Lead Axle High Rail Wheel L/V Nadal--75 1.4 R=1145 ft 1.2 1 0.8 0.6 0.4 0.2 0 0.3 0.4 0.5 0.6 Friction Coefficient Figure 32. Wheel L/V ratio, Type 1 transit rail car, 15 mph, 75 flange angle, perturbation Level 3. Main-line curves with radii less than 500 ft; the speed bations approach or exceed the Nadal value only with a limit is 4 in. cant deficiency under Level 1 perturbations. friction coefficient of 0.6. The flange climb derailment risk is significantly reduced Figure 36 shows the following for the Type 1 light rail vehicle by using 75 flange angle wheels. No guard rail is needed with a 75 flange angle wheel: in yard, and the main-line speed limit can be 7.5 in. cant deficiency under Level 2 perturbations. The dynamic curving L/V ratios for the vehicle running at a From a safety point of view, the 75 flange angle wheel is speed of 15 mph under Level 3 track perturbations exceeded recommended for use in transit vehicles. the Nadal value on curves with radii less than or equal to 755 ft. The dynamic curving L/V ratios for the vehicle running 4.3 Light Rail Vehicles at a 7.5 in. cant deficiency speed under Level 1 track per- turbations were below the Nadal value on all simulated The light rail vehicle also benefits from the use of a steep curves. flange angle (75) wheel. As Figures 34 and 35 show, all The dynamic curving L/V ratios for the vehicle running at simulated steady-state curving L/V ratios for the Type 1 a 4.0 in. cant deficiency speed under Level 2 track pertur- light rail vehicle running on yard curves are far below bations exceeded the Nadal value on curves with radii less Nadal values; the dynamic L/V ratios under Level 3 pertur- than or equal to 500 ft. Friction Coefficient 0.6 1.2 Lead Axle High Rail Wheel L/V 1 0.8 0.6 NADAL Limit 0.4 7.5 inch CD, no pert 7.5 inch CD, pert2 0.2 7.5 inch CD, pert3 15 mph, pert3 0 100 300 500 700 900 1100 Curve Radius (ft) Figure 33. Wheel L/V ratio, Type 1 transit rail car, 75 flange angle, friction coefficient 0.6.* *Refer to Table 5 for the different speeds corresponding to 7.5-in. cant deficiency.

OCR for page 19
20 R=100 ft R=250 ft 1.8 R=320 ft R=500 ft 1.6 Nadal--75 R=755 ft R=955 ft Lead Axle High Rail Wheel L/V 1.4 R=1145 ft 1.2 1 0.8 0.6 0.4 0.2 0 0.3 0.4 0.5 0.6 Friction Coefficient Figure 34. Wheel L/V ratio, Type 1 light rail vehicle, steady-state curving, 15 mph. R=100 ft R=250 ft 1.8 R=320 ft R=500 ft 1.6 Nadal--75 Lead Axle High Rail Wheel L/V R=755 ft R=955 ft 1.4 R=1145 ft 1.2 1 0.8 0.6 0.4 0.2 0 0.3 0.4 0.5 0.6 Friction Coefficient Figure 35. Wheel L/V ratio, Type 1 light rail vehicle, Level 3 perturbations, 15 mph. Friction Coefficient 0.6 1.2 Lead Axle High Rail Wheel L/V 1 0.8 0.6 0.4 NADAL Limit 7.5 inch CD, no pert 7.5 inch CD, pert1 4.0 inch CD, pert2 0.2 15 mph, pert3 0 100 300 500 700 900 1100 Curve Radius (ft) Figure 36. Wheel L/V ratio, Type 1 light rail vehicle, friction coefficient 0.6.

OCR for page 19
21 R=100 ft R=250 ft 1.8 R=320 ft R=500 ft 1.6 Nadal--75 R=755 ft R=955 ft Lead Axle High Rail Wheel L/V 1.4 R=1145 ft 1.2 1 0.8 0.6 0.4 0.2 0 0.3 0.4 0.5 0.6 Friction Coefficient Figure 37. Wheel L/V ratio, Type 2 light rail vehicle, steady-state curving, 15 mph. Correspondingly, for the Type 1 light rail vehicle with a 75 with an IRW in the middle truck was conducted to address the flange angle wheel, the following was determined: safety concerns for this type of vehicle. Figures 37 and 38 show that both steady-state and dynamic curving L/V ratios for all No guard/restraining rail is needed for the vehicle running simulated cases are less than the Nadal values. Therefore, the at a speed of 7.5 in. cant deficiency on curves with radii low-speed curving performance on yard curves by the Type 2 larger than or equal to 100 ft if the track is maintained at a light rail vehicle with a 75 flange angle IRW is even better than Level 1 perturbation standard. the performance by the Type 1 light rail vehicle that used solid Guard/restraining rails should be installed on the following: axles for all trucks. Because the wheelset geometry and wheel Yard curves with radii less than 755 ft; the speed limit is profiles used by both types of light rail vehicles are exactly the 15 mph under Level 3 perturbations, and same, the performance difference must be caused by the dif- Main-line curves with radii less than 500 ft; the speed ferent dynamic behavior between the solid axles and the IRWs, limit is 4.0 in. cant deficiency under Level 2 perturbations. different vehicle structures, and the suspension characteristics. These two types of light rail vehicles behave differently, not TCRP Report 71, Volume 5 (2) showed that the IRW is prone only on low-speed curving, but also on high-speed curving. to flange climb derailment due to the lack of longitudinal creep Figure 39 shows that the IRW L/V ratios generally increase forces. The simulation of the Type 2 low-floor light rail vehicle with the running speed and result in flange climb derailment on R=100 ft R=250 ft 1.8 R=320 ft R=500 ft 1.6 Lead Axle High Rail Wheel L/V R=755 ft R=955 ft Nadal--75 1.4 R=1145 ft 1.2 1 0.8 0.6 0.4 0.2 0 0.3 0.4 0.5 0.6 Friction Coefficient Figure 38. Wheel L/V ratio, Type 2 light rail vehicle, Level 3 perturbations, 15 mph.