Al Kresse wrote:
"By 1928 the standard AAR auto-boxes had changed the clearance
envelope and auto-boxes were starting to get bigger . . . but the
smaller ones would still be around."
Al, do you have a reference to back that statement? Automobile
boxcars c. 1928 were still relatively small cars; the PRR Class X28
were 9 ft 3 in IH cars. The New York Central cars in Earl's post that
were built in 1929 were indeed taller cars at 10 ft IH but lacked
Evans auto loaders.
The appliance that would force the development was the Evans Auto
Loader, which required a taller car to accomodate both the extra
automobiles when loaded and to stow the loader when empty or when the
car was used to handle other freight. Widespread use of these taller
automobile cars would not occur until 1934 with the introduction of
the PRR Class X31 automobile boxcars. The older automobile boxcars
were still around, but they would be bumped from finished automobile
service, with some rebuilt into general service boxcars such as the
PRR Class X28A or N&W Class BPA.