The Educational Railroading Conference Leader Since 1994


2019 Heavy Haul Session


Evolution of Expectations for the Three-Piece Truck

Jon Jeambey

Jon Jeambey
3pctruck Consulting, LLC

The ubiquitous three-piece truck, with its two sideframes and swiveling bolster, has been in the rail industry since at least the 1830's. Its use predates the standardization of the track gauge at four-feet, eight and one-half inches. This longevity is due to its overall simplicity and its remarkable ability to keep its wheelsets on the rails. The four-wheel, two-axle bogie long ago solved the problem of how to make a freight car longer and able to haul more cargo than a Conestoga wagon. Today, the unassuming three-piece truck provides an elegant solution to carrying heavy loads over various track geometries while allowing the wheelsets just enough freedom to use their rolling-radius difference to find and follow the track.

This longevity does not mean stagnation, it means the basic design is adaptable, scalable and reconfigurable. As the business changes, as needs arise, as our understanding of the wheel/rail interface improves, our expectations for the three-piece truck evolve and grow more complex. This presentation examines major shifts in the expectations for the three-piece truck from the fleet owner perspective, during the last twenty-five years.