Re: boxcar design evolution
It would seem that some 1920's cars were built with the USRA type pressed frame members, but many were not. PRR added reinforcing "boots" on the ends of the framing on many X26 USRA designed cars, and IIRC D&H and some others actually replaced the original framing with 'Z' section material during rebuilding. The WWII "War Emergency" designs also seem to have reverted to standard steel shapes. These events could suggest that the USRA type members were not wholly successful. At least by the 1940's it would appear that standard shapes had won out.toggle quoted messageShow quoted text
OTOH, hoppers and gondolas, both composite and all steel, continued to use more specialized shapes in their framing. The early PRR single sheathed designs (R7 and X23) also used special pressed members, so USRA was clearly not the first.
The USRA single sheathed design would appear to have been a step forward in height, as the 1920's ARA standard called for scaling the IH back by 6 inches, with the original USRA size as an option.
--- In STMFC@..., "soolinehistory" <destorzek@...> wrote:
Where are you saying these fit in the evolutionary chain, Rob? The first steel frame boxcars used stock mill shapes, either Z, C, or L section, while some of the last single sheathed composite cars did likewise. The cars with the pressed framing fit in the middle, a good idea that came... and went.