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.
index
contents
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