Recent improvements to three-piece trucks [railways]

The three-piece truck remains the truck of choice for essentially all freight cars in North America. The historic roots of the three-piece truck are discussed. Definitions of the terminology are proposed for the three-piece truck and who is the designer, supplier and assembler of the truck. The conventional truck of the 1950s and 1960s is being displaced by a more modern truck as increased operating speeds, enhanced ride quality and operating cost reductions drive improvements. In the 1990s, the demands for weight reduction, increased loads on the 100 ton truck and increasing car mileage require additional enhancements to the three-piece truck. Several truck designs are being considered by American Steel Foundries (ASF) for future three-piece trucks. Continued development of radial trucks, a new family of 110 ton (286 k lb. gross rail load) trucks, a new variable damped suspension system building on the proven reliability of the ASF Super Service Ride Control suspension and a locked adapter with decoupled lateral (LADL) truck are described in this paper. In summary, this paper contains a brief history of the three-piece truck evolution which focuses upon the truck and suspension designs. The genesis in the arch bar truck is reviewed and the development of the three-piece truck to date is discussed. Finally, some future truck designs are disclosed.