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the Pennsylvania Railroad's 2DF8 truck. The American Railway
Association adopted what was essentially the Pennsylvania
design as its Type Y truck (17). (There was also a similar Type
W truck which, like the Vulcan truck, had separate bolted-in
journal boxes, but it was little used.) Equally important, the
ARA established revised standard specifications for freight car
trucks, including such key dimensions as wheelbase, center
plate height, and side bearing height.
It was soon found that the Type Y trucks were prone to crack-
ing at the lower corners of the spring box, so the Type Y side
frame design was short-lived except on the Pennsylvania
Railroad, which continued to employ 2DF8-style trucks until
the late 1930s. However, other truck manufacturers quickly
developed alternative side frame designs of varying configu-
rations which reduced the cracking problem. All had integral
16
16: Following the end of World War I, Bettendorf
redesigned its integral journal box truck to incorporate U
section rather than T-section side frames, and this was the
forerunner of many similar trucks in the 1920s conforming
to ARA specifications.
Freight Car Trucks - 8
journal boxes, U section side frames, and shallow U-section
steel spring planks, and all conformed with ARA standard
specifications (18 through 25). It is therefore useful to consider
these trucks as ARA "Standard" trucks, as long as it is under-
stood that – apart from the Type Y – none were ever desig-
nated as standard designs by the ARA.
In 1934, when the American Railway Association was reorga-
nized into the Association of American Railroads, the ARA stan-
dard truck specifications became AAR standards. With some
modifications, the AAR standards have continued in effect to
the present day.
Efforts to improve riding qualities
In the first two decades of the 20th century, the size, weight,
and tractive effort of locomotives increased dramatically.
Initially most railroads emphasized using this increased power
17
17: The ARA Type Y truck was an integral journal box truck
developed from the Pennsylvania Railroad's 2DF8 truck,
which it closely resembled. Its popularity was short-lived,
owing to side frame cracks at the lower corners of the
spring box, though the Pennsy continued to produce the
2DF8 and variants for many years.
MRH-May 2013
