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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 20
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 21
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.
