Interface - The Journal of Wheel/Rail Interaction

RAIL TRANSIT

Examining wheel/rail interaction on rail transit systems
(continued)

Wheel squeal was particularly troublesome on The Port Authority of Allegheny County's Gateway Loop, an approximately 119-meter loop with two 25-meter radius curves in the downtown subway portion of the system. These tight-radius curves require the outside wheel to travel more than 16 feet farther than the inside wheel through the curves, Jim Dwyer, the agency's Director - Technical Support, told the seminar delegates. This slippage resulted in high-frequency wheel squeal of 100 dB or more. After trying a number of mitigation measures, the agency settled upon the use of Kelsan Technologies' KELTRACK top-of-rail friction modifier, which reduced noise levels to 85 dB.

At Dorchester Station outside the subway, use of the top-of-rail friction modifier at a transition from a 91-meter radius to a 183-meter radius curve on an 8% grade reduced noise levels from 100-plus dB to 80 dB—"without negatively affecting traction on the grade," Dwyer said.

Richard Reiff, Principle Engineer at the Transportation Technology Center, Inc., presented data on tests of a "drilled hole" approach to gauge-face or top-of-rail lubrication designed for in-street paved track applications. This approach features a 3/16-inch diameter hole drilled at 70 degrees into the railhead through which grease- or soy-based lubricants are applied to the rail in curves. Tests conducted through the Transit Cooperative Research Program (TCRP), a program that was funded to leverage research results from the freight sector and accelerate implementation to the transit industry, indicated that use of the system could reduce the coefficient of friction by approximately 0.2µ from dry conditions to an average 0.33 µ. Observed noise levels were reduced by 2 dB to 16 dB (between 2kHz and 20 kHz).

New York City Transit has adopted a number of measures—both car and track treatments—to mitigate noise and vibration along its more than 800 miles of mainline and yard tracks. The installation of ring-dampened wheels reduced screech noise by 15 - 20 dBA. New, quieter traction motors reduced noise levels another 5 - 7 dBA, and attention to wheel flats further reduced noise. "Trued wheels are 10 - 15 dBA quieter than 'flat' wheels," said Antonio Cabrera, NYCT's Director of Track Engineering.

Joint removal and the installation of cwr, where possible, further reduced noise by 5 - 7 dBA compared to jointed rail. The use of resilient fasteners in subways and on elevated structures reduced noise levels by another 3 - 5 dBA, Cabrera said. Gauge-face/wheel-flange lubrication and top-of-rail friction modifiers at stations, particularly in the underground portions of the system, provided an average noise reduction of 7.3 dBA—an average 5.2 dBA at 31.5 - 200 Hz frequencies, and 13.3 dBA at 1,000 - 20,000 Hz.

"Proper friction management has been shown to effectively reduce lateral curve forces, rail and wheel wear, wheel squeal, derailment potential and energy consumption on rail transit and freight systems," Gary Wolf, President of Rail Sciences Inc. said during his discussion of the Principles of Friction Management. "Other less tangible benefits include reductions in tie and fastener wear, environmental pollution and corrugations."

< PREVIOUS PAGE | PAGE 2 OF 4 | NEXT PAGE >