Interface - The Journal of Wheel/Rail Interaction

RAIL TRANSIT

Examining wheel/rail interaction on rail transit systems
By Bob Tuzik • November 4, 2004

If the first unwritten rule in optimizing the wheel/rail interface on rail transit is: Know your system; the second rule should be: Recognize that the w/r interface is a system.

"No single department can attack the issues in isolation and expect to get very far," Joseph Oriolo, Senior Project Manager - Maintenance-of-Way, Massachusetts Bay Transportation Authority, told attendees at Interface Journal and Advanced Rail Management's Rail Transit '04 Wheel/Rail Interaction Seminar in Baltimore, last month. "You need input and cooperation from Mechanical, Track and Operating people to address all of the issues affecting the system."

And before modifying either the wheel-flange or the gauge-face angle through cutting or grinding, transit engineers should ask themselves what effect a change will have on the other half of the interface, and how the profile shapes will be maintained. What the Mechanical Department does to its wheels affects rail, just as what the Track Department does to its rail affects wheels.

Speakers at this—the first seminar devoted to wheel/rail interaction on rail transit systems — addressed these and other issues, including the "Principles of Wheel/Rail Interaction" in the areas of Vehicle/Track Interaction, Wheel/Rail Profile Design and Maintenance, Friction Management, and Noise and Vibration.

"Noise is the lightning rod of discontent on rail transit systems," said Carl Hanson, Senior Vice President of Harris Miller Miller & Hanson Inc. Whether characterized as rolling, the most ubiquitous type of wheel/rail-generated noise, impact or squeal, the type which generates the most complaints, noise is a byproduct of rail operations. Excessive wheel/rail-generated noise can be controlled, however, by addressing the frequencies that are generated by wheel and rail roughness wavelengths and train speed.

Rolling noise is best addressed by keeping wheel and rail surfaces smooth, including preventing the occurrence of rail or wheel corrugations — or at least treating corrugations before they grow — Hanson said. Impact noise can be addressed by using cwr, aligning joint and frog surfaces to minimize impacts, and adjusting frog surfaces to make for smooth load transfer between different load-bearing surfaces. Squeal noise is best addressed through effective lubrication/friction management and optimized wheel and rail profiles.

Some systems have adopted the use of ring- or fin-dampened wheels that are tuned to control resonant frequencies and reduce noise, said Jim Nelson, Vice President - Principle at Wilson, Ihrig & Associates, Inc. Wheel vibration absorbers were shown to reduce under-car noise by an average 7 decibels (dBA) at the leading truck negotiating a large radius curve at 40 mph on one transit system. Wheel-flange/gauge-face lubrication and top-of-rail friction control have also been shown to provide effective noise control — especially at high frequencies where hearing is most sensitive.

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