In it for the long haul: suppliers are revamping their freight car trucks to carry today's 286K GRL cars and meet AAR's new M-976 performance spec requirements

Railway Age, March, 2004 by Marybeth Luczak

The aim of AARM 976--the Association of American new truck performance specification for the flee interchange of 286,000-pound gross rail load cars--is to improve the stress state of the railroads, mitigating the increased damage that heavier cars inflict on rail infrastructure. Last year, AAR's Equipment Engineering Committee approved two suspension systems under the new spec: Amsted Rail Group's Motion Control[R] Truck System (RA, January, p. 67) and Standard Car Truck's (SCT) Barber[R] S-2-HD Sprit Wedge Truck, according to Charles Powell, AAR committee coordinator. AAR recently completed successful testing of another suspension system using SCT components--the S-2-E Truck with 945 split wedge (an M-976 equivalent system limited to open-top hopper cars or high-sided gondolas having a center of gravity of lower than 93 inches) and S-2-E Truck with standard, one-piece 917 friction wedge (approved for all car types)--and officially published the approval letters late last month.

The new trucks, developed during spring and summer 2003, were based on existing designs. One reason for this strategy was the "short timetable" that suppliers had to meet AAR's criteria, says David East, SCT's vice president-engineering.

Another was for customer ease. "We want to provide trucks that our customers are accustomed to rising, so we've focused on upgrading our existing components in the same [casting] box," says Armand Taillon, SCT's director-research and development.

"The advantage is that when trucks already in service have to be reconditioned, they can be converted to meet M-976 requirements, and that's attractive to certain customers."

SCT's line of Barber[R] stabilized, variable-damped, lightweight freight car trucks for high speed, heavy-axle load service includes the S-2-HD with split wedge (M-976 approved); S-2-E with 945 split wedge (M-976 equivalent approved); S-2-E with standard, one-piece 917 friction wedge (M-976 approved); and S-2-D with split wedge (in test for possible M-976 approval).

The S-2-HD three-piece truck was introduced almost 30 years ago, following development of the lower-cost Barber $2 truck line in the 1950s, according to Taillon. The HD offered long wearing stainless steel wear plates in the bolster pockets, a "wide land" reinforced sideframe, and friction castings with 27% more friction area. The S-2-D was added to the Barber stabilized truck product line in the late 1980s as a more economical heavy-axle load alternative to the S-2-HD. It offered the same performance as the HD at a lower cost, by increasing the wedge friction area and eliminating the pocket wear plate.

Now, constructed with Pennsy Corp.'s AdapterPlus roller bearing adapters for better curving performance, and optimized spring group and wedge, the S-2-HD Split Wedge Truck meets all AAR approval requirements and is suited for high mileage environments, says David East. TTX Co. tested the truck for use in its own fleet--including standalone wells, bulkhead flats, centerbeams, and boxcars--and sponsored it for approval by the AAR.

As axle loads increased in the mid 1990s, SCT began manufacturing the S-2-E "three-piece radial truck" with an economical 917 standard wedge or 945 split wedge--an extra large friction wedge (8-1/2 inches) for high durability and longer suspension component life. The S-2-E with 945 split wedge "balances damping to control the vertical dynamics of the car and warp resistance to control the lateral dynamics," Taillon explains. Both versions get their radial curving performance from the SCT LC pedestal shear pad (LC pad). The LC pad combines three steel plates with vulcanized rubber to provide primary suspension shear flexibility that allows wheelsets to steer through curves. (LC pads have been in use on various Barber trucks since floe mid 1980s.)

The S-2-HD, the S-2-E, and the S-2-D were all tested at the National Research Council in Canada prior to undergoing certification tests for AAR M-976 approval. "It was a trial and error process to get the best combination of components and modify and improve those combinations to best suit the overall requirements of M-976," Taillon says. Of particular note, he reports, the curving track rolling resistance performance of each truck tested ranged between 0.17 and 0.28 pounds per ton, per degree of curvature--well below the spec's maximum requirement of 0.4. SCT is now taking the test results and applying them to a brand new truck design, according to East. Testing is slated to start later this year.

Amsted Rail Group--comprised of Griffin Wheel Co., ASF-Keystone, Inc., and Brenco, Inc.--also offers an M-976-approved truck: Motion Control. It incorporates such components as the Pennsy AdapterPlus steering pad; Spring Control[R] steel spring, long travel constant-contact side bearing; Motion Control tuned suspension; Griffin O.E. curved plate, Class C wheel; Brenco Generation 2000 Class K bearing; wide-shaped 6 1/2-inch by 9-inch Super Service Ridemaster friction shoe; and lightweight, tight-tolerance truck casting.