Examining Wheel/Rail Interaction (continued)
The TTCI found a number of anomalies, such as mis-matched side frames, high wedges, worn or broken springs and liners, and poor constant contact side bearing (CCSB) clearance (illustrating a benefit to be gained from use of long travel CCSBs) in the suspension systems of the cars it tore down. It also identified issues at the truck/carbody interface. The TTCI observed chatter marks on the side walls of certerplates on which the carbody was binding, unevenly worn ceterbowl liners and, in some cases, off-center bolsters. As a result, some cars simply seem to "prefer" left hand curves over right hand curves. The insight provided was such that the TTCI has come to the conclusion that the truck/carbody interface, in some cases, may be as important as the wheel/rail interface, Tournay said.
The TTCI is also developing an automated Wheel/Rail Contact Inspection (WRIC) system to help identify and prevent vehicle hunting and flange-climb derailments, gauge widening and rail rollover, and rolling contact fatigue (RCF). The system sends rail profile measurements collected by an automated system, along with previously collect wheel profiles, to WRTOL™ software to determine conicity levels and monitor the effectiveness of rail profile grinding programs. While finding the root causes of poor wheel/rail, vehicle/track interaction drives research, controlling the cost of wheel changeouts associated with high impact loads is a primary goal of private car owners.
"With the supply-and-demand-driven price of steel, wheelset pricing changes monthly," said Dennis Weed, Chief Mechanical Officer at Chicago Freight Leasing Co. "This makes long- and even short-term planning difficult."
With a fleet of nearly 8,000 cars, the cost of wheel changeouts is significant. In one seven-month period, 880 wheelsets were changed out, due to high kip readings by Wheel Impact Load Detectors (WILD). The cost translates to millions. Consequently, Chicago Freight Car Leasing has been involved in developing tools and software to analyze the condition of the wheelsets in its fleet over the past several years. Changes to AAR Interchange Rules and the advent of the Maintenance Advisory System to alert car owners of potential problems using WILD data have provided new avenues to approach maintaining railcars for the industry.
"If we can keep cars within the 40-kip range, we’ll be okay," Weed said.
Tread-conditioning shoes may help achieve that, Weed said, as will better wheel-impact monitoring. Toward that end, Chicago Freight Car Leasing has begun remotely monitoring the braking performance of select equipment in its fleet. The system will identify significant "events" that occur over the system and help identify the root causes.
The shape and condition of the wheel tread affects passenger vehicles as well. The American Public Transportation Association (APTA) PRESS Committee's "Wheel Tread Taper" working group has been formulating a standard definition of conicity that will enable transit/commuter agencies to evaluate wheel/rail pairing in terms of vehicle stability and curving. These definitions, which were presented by Brian Marquis, research engineer at the Volpe Center, are intended to help railroads assess the contact conditions resulting from combinations of new and service-worn wheel and rail profiles. They will also assist in choosing new wheel profiles and establishing maintenance limits that meet the stability and curving requirements of a particular operation. The committee will present the final recommendations to APTA for review by end of this year.
