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2
2: This typical early 20th century arch bar truck had
symmetrical top and bottom chords, cast steel bolster
and columns, and a steel channel spring plank with
oak spring seats.
Arch bar trucks
The first arch bar trucks began to appear in the 1860s.
Originally the side frames were made of iron bars bolted
together, and bolsters and spring planks were wood. The arch
bar design was adopted almost universally in the years that fol-
lowed, with improvements that included iron and (later) steel
bolsters and spring planks, steel side frame bars, and longer
wheelbases. The arch bar truck had a number of advantages
over other freight car truck designs. It was simple and inexpen-
sive to make, and it rode and tracked well. Moreover, as freight
cars became larger and heavier, the arch bar truck's load-car-
rying capacity could be increased simply by making the com-
ponent parts larger. [For more information on the evolution of
trucks in the nineteenth century, see John H. White, Jr.'s The
American Railroad Freight Car, Johns Hopkins University Press,
Baltimore, 1993.]
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