Interface - The Journal of Wheel/Rail Interaction

FRICTION MODIFICATION

Top of Rail Friction Modification in Tough Terrain (continued)

The lateral force and friction data collected in this and other studies (2) indicated that the TOR friction modifier reduced lateral forces and rail wear primary through wheel conditioning, which occurs as the dry film produced by the friction modifier is transferred to the wheel treads. This led the group to investigate the degree to which the application of tread brakes disrupts the effectiveness of the friction modifier film (see Figure 8).

Figure 9 summarizes the results of tests performed over several months to determine whether an increase in film thickness could prolong film integrity during air braking. The vertical axis indicates the average values of peak lateral forces associated with the leading axles of loaded cars. The horizontal axis shows various conditions, from baseline (dry top-of-rail, with gauge-face lubrication only), to TOR application at 70%, 100% and 140% of the typical (river grade) net application rate. The results show that increasing the TOR application rate to 140% of the nominal value was sufficient to overcome the effects of air braking and deliver the target 30% force reductions that are expected from the use of a TOR friction modifier in sharp curves. The tests also confirmed prior reports (2) that the use of multiple wayside TOR units can effectively condition wheels to significantly reduce lateral forces.

Finally, a study of the applicator “wet zone” geometry determined that the use of one TOR-XL applicator bar per rail (versus two per rail as shown in Figure 6 - on previous page) can provide fully effective friction control. This reduction in hardware can reduce cost and complexity as well as the effort required to remove the wayside systems for track maintenance. (Note: The results of these tests apply to the specific material properties and drying behavior of KELTRACK® Trackside Freight.)

Test Area 2: Ascending Grades
The second test area in this study, on the double-track mainline coal route near Maybeury, West Virginia, was chosen to evaluate the performance of the TOR friction modifier on ascending grades with heavy locomotive sanding. In this case, a lateral/vertical force measurement site was installed in a 4.5-degree curve, and five dual-track TOR application sites were installed at distances up to 2.5 miles from the measurement site. Guided by an optimization matrix, the general testing approach was to sequentially shut down units and determine lateral force reductions at a range of distances (application rates were set to maximize benefits in the absence of tread braking). The analysis focused on eastbound loaded coal trains.

Table 1 displays the lateral force reductions at distances as a fraction of d_typ(the typical unit spacing in river grade territory). The target 30% lateral force reductions were achieved at distances up to 70% of typical river grade spacing. These results verified the effectiveness of the KELTRACK material (with minor adjustments to unit spacing) in the presence of heavy sanding. Figure 10 shows the distribution of the low rail lateral forces under baseline conditions (gauge face lubrication only) and TOR-treated conditions, with a clear shift in the distribution toward lower values with TOR friction control implemented.

While application of the TOR material clearly reduced lateral forces in the 4.5-degree curve, an unexpected and substantial portion of the baseline distribution exceeded 10 kips. And while the spike breakage associated with high lateral loadings had been reduced in the TOR application areas, it had not been eliminated as hoped. These observations led to the analysis of the roles of train speed and superelevation.

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