Interface - The Journal of Wheel/Rail Interaction

FRICTION CONTROL

Controlling Top-of-Rail Friction (continued)

There have been very few demonstrations of hi rail-based systems. BC Rail sponsored one demonstration and Burlington Northern Santa Fe is considering an extended demonstration. To date, the hi rail-applied material appears to be effective for five to eight trains after application, requiring a too frequent reapplication rate for a 40- to 50-mgt line. While suppliers are working to improve the durability of the material, at present, hi rail application appears to be viable only for lower tonnage lines.

While the AAR did not analyze the data, it appears that this approach to TOR friction control also contributes to a significant reduction in rail wear. Norm Hooper, BC Rail's vice president of maintenance and chief engineer, told the International Heavy Haul Association in May of last year that gauge face and head-loss wear rates were reduced by 60% - 75%, depending on the degree of curvature, since the introduction of its TOR friction modifier application program. Material was applied every second day or approximately every 3,500 axles.

Generally, application of TOR friction modifiers appears best suited to wayside application, since the track department, which is generally tasked with maintaining lubrication and friction control on the railroad, is very familiar with wayside applicators. Wayside systems are also well suited to addressing site-specific conditions, such as curves. The AAR/TTCI has evaluated carry distance from wayside applicators, output rates, and variability in deployment on single and bi-directional lines.

BNSF installed a pair of TOR applicators on a bi-directional line with mixed traffic at Keddie, Calif. Applicators were initially spaced and monitored at 1,900 feet, then 3,900 feet and finally 5,500 feet apart. (A new rail installation interrupted the test before the applicators could be monitored at 9,000-foot spacing.) During the tests, curving forces were measured on a 10-degree curve with traditional wayside lubricators already in place. When the TOR friction modifier was added, the forces measured under loaded cars with an average wheel load of 25,000 pounds dropped by 50% or more—even as the applicators were spaced farther apart. New rail was less affected than worn rail. The primary reason for this is that the contact patch was much wider on the old conformal rail than on the new 141-pound rail—about 40 mm on the old compared to 15 mm on the new low rail, and 50 mm on the worn conformal rail compared to 20 mm on the new high rail (see Figure 1).

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