Interface - The Journal of Wheel/Rail Interaction

RAIL GRINDING

Specialized Rail Profile Grinding on MBTA (continued)

"The wear pattern in tangent track was a lot like that of the high rail in curves," Bachinsky says. A by-product of grinding off the shelf was a slight increase in flange clearance, which helped increase rolling radius difference.

ARM/RESCO designed a series of new profiles with 3/8-inch running bands to take better advantage of rolling radius difference and thereby improve steering (see Figure 4). Multiple contact points reduced point loadings and the potential for rolling contact fatigue; the profiles also spread the wear to help maintain the tread shape and surface of the wheel.

"By varying the contact position in curves and in tangent track, through a well-designed grinding and profile strategy, we can produce a more effective wear pattern over the wheel profile," RESCO President Roy Smith said. "This helps to prolong the life of the wheel profile."

Other objectives of the new profiles were to:
• Avoid two-point contact situations as much as possible.
• Create sufficient rolling radius difference to promote steering and avoid anti-steering.
• Avoid excessive effective conicity.
• Avoid the development of extremely wide contact patch.
• Avoid sharp gauge corner radii and contact too near the gauge corner.

In the simplest sense, the best way to prevent the flange angle from degrading is to prevent contact with the gauge face. "If the flange doesn't touch the rail, it can't wear it and it can't change it," Oriolo says.

ARM developed a grinding map in which various profiles were used, depending on geometric configurations. With the new profile grinding strategy in place, vehicle steering has improved and gauge-corner flange contact virtually has been eliminated in all but 600-foot radius or tighter curves. (This applies only to steered wheels with traditional, solid-axle trucks. The Independently Rotating Wheels on the low-floor cars are not responsive to the steering forces that apply to conventional trucks (see Flange Climb and Independently Rotating Wheels).) With that, wheel flange wear has been reduced dramatically.

"We have now gone approximately 10,000 miles without needing to true a wheel," Oriolo said. "Thus far, we're seeing an approximate 300% increase in mileage between wheel truing cycles."

Most satisfying, perhaps, is that with the IWP and the rail profile grinding program in place, new positive wheel and rail patterns are beginning to emerge. Formation of the shelf on the gauge-face of the rail has significantly reduced. When it reappears, it forms a steeper gauge face angle than previously observed. Instead of wearing shallow, wheel flanges are wearing to the steeper end of the range. "The flanges are going from 63 degrees up to 70 degrees in some cases," Oriolo says.

MBTA is monitoring wheel flange angle wear diligently and recently installed WheelScan, a real-time wayside measurement system produced by KLD Labs Inc., that uses a combination of lasers and video cameras to capture wheel profiles on the system. The data will be integrated into ARM's optical rail measurement database to analyze wheel/rail interaction.

"This has been a rewarding and real learning experience," Oriolo said. "We started with a wheel/rail problem, but we needed the cooperation of all departments, car equipment, m/w, transportation—and our suppliers—to solve it." There is still work to do, he says, "but we have made significant progress in optimizing our wheel/rail interface."

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