Interface - The Journal of Wheel/Rail Interaction

RAIL GRINDING

Specialized Rail Profile Grinding on MBTA (continued)

The MBTA hired Advanced Rail Management to come up with a solution. ARM worked closely with its subcontractor Loram Maintenance of Way, Inc., to design a program to meet the MBTA's needs.

"Our goal was to grind as near vertical as possible on the gauge face of the rail," says ARM President Gordon Bachinsky. "We could see that a 10- to 15-degree gauge-face angle would mate well with a 75-degree flange angle on the wheel." (See Figure 2.)

Loram modified two of its L-Series grinders, which feature four 30-hp motors (two per rail) on each grinding cart, to perform the task. It adopted the use of grinding stones with a 1-inch wall (in place of 2-inch wall stones that are more commonly used) in order to remove the shelf that had been cut into the rail by the wheel flanges. But that wasn't the only problem. Normally, the weight of the grinding motor provides much of the force required for grinding. But with the motors positioned at 80 degrees to remove the shelf and grind the gauge face of the rail, they couldn't provide enough grinding force.

"We put springs on the modules to pull them inward and provide downward grinding pressure against the rail," says Don Minge, manager of Loram's Light Rail Division.

The initial effort to remove the shelf on the gauge face of the rail required 40 - 50 passes. Soon after the grinding work started a second grinding cart was added to provide 8 motors (four per rail), overall. In order to hasten the process, the MBTA for some period used two grinding units (see Figure 3), each with two grinding carts (with four motors per cart.)

Removing the shelf on the rail required constant attention. There were many wheels with the old 63-degree flange angles operating on the line until they could be turned to the new IWP. These wheels tended to re-cut the shelf that the grinder was eliminating and wear a high-degree angle on the gauge face of the rail. As more cars came on line with the new 75-degree IWP, less damage was done to the rail, but additional work was required to break the cyclical pattern of gauge-face degradation. Once all of the wheels operating on the B Segment (Commonwealth Avenue) of the Green Line were re-profiled to the IWP, ARM began profile grinding the running surface of the rail to promote vehicle steering and prevent wheel-flange/gauge-face contact.

Rail Profile Grinding
Working with its subcontractor RESCO Engineering, ARM designed a series of new rail profiles for curved track to promote steering in curves down to approx. 600-ft radius. ARM and RESCO also performed a pummeling analysis to design a series of profiles to promote better steering and correct the sinusoidal, side-to-side movement of the vehicles. The sinusoidal movement was exacerbated by tight flange clearance of 5/32 inches, versus a more standard clearance of 7/16 inches on heavy rail, which reduced the ability to generate rolling radius difference in curves. The existing flat and wide contact band that in some cases encompassed the full head of the rail provided evidence that the vehicles were unsteered.

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