Interface - The Journal of Wheel/Rail Interaction

RAIL TRANSIT

Examining wheel/rail interaction on rail transit systems
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Rail corrugation is the most-often cited reason for rail grinding on transit systems, Larry Daniels, Railroad Consulting Engineer, told the seminar delegates. "About 41% of transit track is prone to corrugation. Tangent and curved track are equally prone, although standard carbon rail is more likely to develop corrugation than higher-hardness premium rail," he said. The use of premium rail and an effective lubrication/friction control program are the most effective means of mitigating corrugation. Once it occurs, however, grinding is the only way to get rid of it.

There are two basic types of rail grinding: corrective, which is performed to reduce or eliminate noise and vibration caused by corrugations; and preventive, which is performed to improve and maintain ride and wear characteristics before the onset of corrugation or other conditions requiring corrective action occur.

"Transit systems have a greater ability to optimize the wheel/rail interface than freight systems that have to deal with a wide range of wheel profiles on interchanged cars," said Gordon Bachinsky, President of Advanced Rail Management Corp. Still, he said, every property is different and requires a unique set of profiles depending on the type of vehicles, track structure and operating parameters on the system. The first step in understanding what's needed is to measure some percentage of the wheel and rail profiles on a given system.

Wheel measurements may be taken manually, with simple go/no-go templates or with precision contact or non-contact laser-measurement systems. Wayside measurements systems such as KLD Labs, Inc.'s WheelScan system, which uses a combination of lasers and video cameras to profile and measure wheels at operating speeds, are also available. A WheelScan system is in final commissioning stages on the MBTA in Boston.

Rail measurements also can be taken manually, using templates or taper gauges to measure vertical rail height and side wear, as well as the crown radius. Vehicle-mounted automated optical rail measurement systems that collect data as frequently as every 6 inches, if needed, along the rail are also in regular use on transit systems in North America.

"These systems are excellent tools for looking at a lot of data to determine how wheel and rail profiles are performing over time," Bachinsky said. "This enables those responsible for rail and wheel maintenance to determine whether their grinding and truing are effective and if their planning is on target."

There are two types of wheel cutting, or truing, methods: milling and lathe cutting, Oliver Cone, a consultant to Amtrak and Northeast Corridor on wheel truing and diagnostic systems, told the seminar delegates. Milling equipment, which profiles the wheel tread surface in one cut, typically leaves a rougher surface finish. Wheel lathes, which use a stylus to cut the proper profile across the tread, typically leave a smoother surface finish. Underfloor wheel lathes are suitable for turning the treads up to the top and rear face of the flange, machining the inner faces of the wheels, and unilateral re-profiling of one wheelset.

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