On Dec 15, 2006, at 10:48 AM, Kurt Laughlin wrote:

In the last few days I've gotten some back issues of the RPC and taken a good look at some of the files here and on the Steam Freight Cars site, all of which has left me a little confused about how various AAR boxcars are defined.

As best as I can tell, there were four main types: 1937, 1937 (modified), 1944, and postwar. What distinguishes theses from each other? I'm pretty sure that 40-6 x 9-2 x 10-0 cars are the 1937 types and that 40-6 x 9-4 x 10-6 cars are postwar, but what are the others and how much leeway in dimensions is there within a type?

Kurt, your analysis is essentially correct, though there were actually five main variations: 1932, 1937, 1937 modified, 1944, and postwar. the 1932 cars were 9'4" high inside, the 1937 versions were 10'0" high inside, and subsequent versions were all 10'6" or thereabouts. Minor variations in inside dimensions are seldom significant, as they generally reflected nothing more than the application of different roofs (e.g., Viking corrugated instead of Murphy rectangular panel)) or differences in the thickness of wood floor and interior linings. Hence some 1937 modified cars were 10'4" or 10'5" IH, but in any case the salient spotting feature was 5-5 Dreadnaught ends. The shift from 1937 modified to 1944 wasn't recognized by the AAR, since construction and dimensions didn't change, but modelers use the 1944 designation to identify cars with postwar 4-4 Improved Dreadnaught ends. "Postwar" is tricky; I assume it represents the shift to the later style Dreadnaught ends with straight-tapered main ribs and rectangular top rib, but of course many cars of the 1944 design were built after WW II and what you're identifying as "postwar" AAR cars didn't appear until the 1950s.

Richard Hendrickson