Interface - The Journal of Wheel/Rail Interaction

VEHICLE SUSPENSIONS

Improving Truck Designs to Reduce Forces Transmitted to Track
July 21, 2004

The growing number of 286,000-pound (36-ton axle load) rail cars operating in captive and interchange service across North America is putting a lot of stress on the system—on both the track structure and rail cars. Until recently, most of the 286k cars in service utilized conventional suspension systems that were designed years ago for 50- to 90-ton capacity cars.

"We kept increasing the capacity of the cars but had not done a lot with the suspension systems," Thomas Berg, Vice President - Engineering and Product Development at Amsted Rail Group - ASF-Keystone Products, told delegates at Advanced Rail Management/Interface Journal's annual Rail/Wheel Interface Seminar. (Berg delivered the remarks on behalf of Rick Stauffer, Burlington Northern Santa Fe's Director - Reliability Engineering.)

While tests have shown that it is possible to improve track strength to accommodate the increasing number of 286k cars, upgrading the infrastructure on Class 1s and short lines will take time and money. A more cost- and implementation-effective way to reduce wear and tear on the system is to improve heavy car performance.

Phase 3 testing at the Transportation Technology Center, Inc.'s (TTCI) Facility for Accelerated Service Testing / Heavy Axle Load (FAST/HAL) program showed that cars with improved suspension systems reduced track degradation. Phase 5 testing, which incorporated premium track, but with conventional three-piece trucks, indicated that strengthening the track without improving suspension systems was not as effective in reducing the stress state.

"Compared to operations with premium suspension systems, lateral loads increased by 45% and rail wear increased by 500%; tie cutting, rail spalling and fastener problems also increased," Berg said. "Improving track structures without also improving truck suspension systems appears to be a losing proposition."

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