Interface - The Journal of Wheel/Rail Interaction

FRICTION CONTROL

Drilling Down to Top-of-Rail Friction Control (continued)

Noise reductions of about 15 decibels (dB) on average were measured at 200 feet from the applicator; reductions of about 10 dB were measured at 1,200 feet from the applicator. A comparison of noise reductions at various frequencies between dry and steady-state lubricated conditions indicates that noise levels dropped 3 - 5 dB at 2,000 hertz (kHz), 6 dB at 5,000 kHz, 10 dB at 10,000 kHz, and about 20 dB at 15,000 kHz (see Figure 3).

While track-maintenance personnel tend to balk at drilling a hole in the head of the rail, fatigue does not appear to be an issue. Finite Element Analysis was conducted, using a worst-case, hypothetical 20,000-pound wheel load (typical wheel loads on the Tri-Met system are about 14,000 pounds). With no hole in the rail, this wheel load would generate a 6,100-psi contact stress. With a hole in the rail, the wheel load would generate a 21,000-pound load. An arbitrarily doubling of the load to account for a dynamic factor generates about 42,000 psi at the hole. Since the fatigue strength of the rail steel is about 74,000 psi, these applications appear to be well below the danger level on tangent track where there is no lateral loading. Adding a 14,000-pound lateral load to simulate a curve, however, pushes the rail steel near its yield strength at the hole. So, Reiff said, it is important to understand that the installed location of this type of system is significantly limited to installations in tangent track without hunting-induced lateral loading.

This article is based on "Alternative Application System for Lubricating Street/Embedded Track in the Transit Environment," a presentation by Richard Reiff, Principle Engineer at the Transportation Technology Center, Inc., at Interface Journal and Advanced Rail Management's Rail Transit '04 Wheel/Rail Interaction Seminar.

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