Sideframe

A sideframe is the cast side member of a three-piece truck. There are two sideframes per truck, one on each side, and together with the truck bolster and the spring groups they make up the three main castings the truck is named for.

Where It Sits

Each sideframe runs lengthwise along one side of the truck and bridges the two wheelsets at that side. At each end of the sideframe is a pedestal jaw that sits down over a roller bearing adapter, which in turn rests on the roller bearing of the wheelset. In the middle of the sideframe is an open window, the spring seat, where the spring group stands. The bolster passes through that window and rests on top of the springs.

What It Does

The sideframe transfers the load it receives from the bolster down through the springs and out to the two wheelsets, so the car weight reaches the rail through the bearings. Because the bolster floats on the springs rather than being bolted to the sideframes, the sideframe must also guide and hold the bearing adapters as the truck warps to follow curves.

Wear and Inspection

Wear surfaces such as the pedestal roof are protected by a pedestal wear liner, and the brake beam guides carry a brake beam wear liner. Cracks, broken lugs, and worn sections are condemnable under the AAR interchange rules and field manual.