Abstract: A tank car stub sill underframe is assembled by welding together a pair of angles to opposite edges of a longitudinally extending curved plate to form a generally channel-shaped section. The channel-shaped section includes a concave top plate and a pair of vertically extending legs welded to the concave top plate. Each leg includes an outwardly extending, horizontal flange at the base of each leg. The curved plate includes a first portion extending from the end of the car inboard to a point adjacent, but outboard of, the car body bolster in which the curved plate spans the distance between the vertical legs and each of the plate's transverse outer edges engage the upper end of one of the vertical legs. The curved portion includes a second or intermediate portion extending from the inner end of the first portion through the body bolster area and continuing considerably inboard of the bolster area.