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36
36: Applied to a car built in 1936, this Pennsylvania
Railroad truck with coil and elliptical springs was a direct
descendant of the ca. 1920 2DF8 design, which the
Pennsy continued to use long after other railroads (and
the ARA itself) had abandoned it because its side frames
tended to crack.
the leaves so that they tended to act as snubbers and damp
out excessive jolts and oscillation.
AAR Self-Aligning Spring-Plankless trucks
The need for further research and development in the design
of freight car trucks continued into the early 1930s, but owing
to the effects of the economic depression, individual truck
manufacturers lacked the capital to pursue it on their own.
This led to formation of a consortium of truck manufactur-
ers under the Four Wheel Railway Truck Agreement. All of
those who participated in that agreement contributed to the
research, and all were able to employ the resulting improve-
ments without paying royalties.
The outcome of this initiative was the Self-Aligning Spring-
Plankless Double Truss truck, whose innovations combined to
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