A Riveting Solution

Most of Union Pacific's 40 and 50-foot boxcars constructed during the 1930s-50s shared many similarities with adopted AAR standards, but there were some important differences. One of the unique features that Union Pacific modelers have long had to overlook, was the alternate center rivet (ACR) pattern on UP's boxcars. In an effort to reduce the light weight of their new, all-steel boxcars, UP used lighter side sheets, but this required an additional interior post to maintain side strength, and subsequently, an additional row of rivets was present between the seams on the car side. Further, many of the 50-foot automobile cars had yet another style of rivet pattern, commonly referred to as twin alternating rivets, or TAR. This row of rivets was located much closer to the seam, and was found on the A-50-14/-15/-17/-18 series of 50-foot auto cars. Although unusual,  the 40-foot A-50-19s, and the 50-foot B-50-44s had both ACR and TAR.

This photograph of the side sheets of B-50-54 108875, rebuilt from a B-50-39 in 1965, clearly illustrates the ACR rivet pattern. Hooper, NE, August 2010.

Although models of the AAR standard cars have long existed from Red Caboose, Intermountain, and Branchline Trains, the distinctive ACR pattern was overlooked until Marklin / Trix released a model of the B-50-24/-27s. Resin kits from Sunshine and Speedwitch were also available, with ACR, but for UP modelers, the development of Archer Fine Transfers decal sheets with rivet head detail correctly spaced for ACR, finally made it possible to realistically model a fleet of UP boxcars with the distinctive rivet pattern characteristic of UP's postwar freight car fleet.