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improve performance, increase strength, and reduce weight.
Self-alignment was accomplished by attaching the bolster to
the side frames with interlocking, precisely-machined joints,
thus eliminating the need for the spring plank (37). The double
truss eliminated side frame cracking problems by boxing in the
lower chords and extending a rib down the tops of the chords
into the spring box (38 and 39). In the mid-1930s and '40s Self-
Aligning Spring-Plankless Double Truss trucks replaced earlier
truck designs on many new freight cars, despite their some-
what increased cost.
37: Made by American Steel Foundries in the 1930s, this
truck was self-aligning and spring-plankless but did not
have double-truss side frames; the lower chords had open
u-sections and were not boxed in. Note the replaceable
wear plates between the bolster and side frame.
38: A 50-ton self-aligning spring-plankless double-
truss truck, employing all the features developed by
the consortium of truck manufacturers under the four-
wheel Railway Truck Agreement. The arrangement
of five spring clusters with one in the center was an
37
Freight Car Trucks - 15
index contents
MRH-May 2013