Hello:Despite superficial similarities, the two were completely different in both
design and dimensions. The proposed (but never adopted) ARA standard steel
box car of 1924 was essentially a slightly revised Pennsy X29 (at the time
it was proposed, Pennsy people dominated the ARA's Car Construction
Committee). After this car was twice rejected by the mechanical
departments of the ARA's member railroads, a number of railroads had cars
built to the design (or some modification of it) anyway; I'm currently
working on an article which will describe and illustrate those X29 clones,
some of which had various types of proprietary roofs and Dreadnaught ends
instead of the flat riveted types that came off the PRR drawing boards.
The Pennsy went off in a huff, refused to participate in any further
efforts to design an ARA standard car, and ended up building ±30,OOO X29s
for its own use.
Ironically, the brunt of the effort to develop a standard steel box car
that the ARA member railroads would accept was then carried out by the
Pennsy's arch-enemy, the New York Central, and what became the 1932
standard car was the result. It had a much stronger underframe and
distinctive "notched" side sills which resulted from elevating the body
sills above the level of the floor and connecting the bolsters and
crossties to the body by means of tabs extending down below the sills.
This was done because both the X29s and the somewhat modified USRA standard
steel box cars built by the NYC in large numbers during the 1920s trapped
water at the bottom of the sides, causing the steel sheathing to rust out.
At the time the 1932 design was proposed for adoption, there was a great
deal of controversy over its height. Some major RRs wanted taller cars,
but that would have required some smaller lines to enlarge their lineside
clearances, involving in some cases rebuilding bridges and tunnels, and in
the depths of the economic depression this was not a popular idea.
Consequently, the 1932 ARA standard steel box car was only 9'4" high
inside. By 1936, however, a number of RRs were ordering cars of this
design with interior heights of up to 10'0", the lines that had restricted
clearances were essentially forced to enlarge them, and in 1937 a revised
version of the standard design was approved with an inside height of ten
Most of the cars built to the 1932 ARA specs had 4-4 Dreadnaught ends and
Murphy panel steel roofs, but there were numerous exceptions. CGW had them
built with corrugated ends, NS and NKP got them with Viking roofs, etc.
And the Seaboard and L&A ordered them with flat riveted ends and roof,
which made them look more like the Pennsy X29s than they actually were.
Richard H. Hendrickson
Ashland, Oregon 97520