“Alternating Center Rivet” (or “ACR”). Fans of freight cars have used these terms to describe boxcars built with a unique side construction. Because these cars were built using thinner side sheeting to save unladen weight, they required additional support posts behind the sides requiring an additional row of rivets down the middle of each side panel. These added vertical rows of rivets were generally spaced twice as far as the rivets along the panel edges, giving an alternating pattern and a unique appearance.

The railroad which had the most boxcars built with lightweight “ACR” construction was the Union Pacific. In the years just before and immediately following World War II the UP built numerous classes of forty- and fifty-foot boxcars using this lightweight design. The postwar cars make up a particularly interesting group for historians and modelers. They span a period when standard boxcar ends and roofs were undergoing design changes, as were the UP’s paint and lettering practices, creating interesting variations from one group to the next.

Rapido Trains is proud to release a series of these postwar Union Pacific “ACR” 40’ boxcars in classes B-50-39, -41 and -42. Featuring all-new tooling developed with the aid of UP freight car experts, this is the first time that these important classes have been available in HO plastic. Each group of cars offers unique components and/or lettering that showcases the changes that occurred on the prototypes over just a few years. We have designed two styles of roof, two styles of end, four styles of brake wheel (with the correct corresponding housings).