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There was one drawback to the arch bar design, however.
Because it was assembled entirely with bolts and nuts, vibra-
tion could loosen the nuts, and constant working of the truck
could enlarge the bolt holes until the truck would become out
of alignment or, in the worst case, come completely apart. This
shortcoming was becoming increasingly problematic by the
turn of the century, owing in part to the dramatic increase in
car size and capacity that followed the universal adoption of air
brakes and knuckle couplers. The tendency of arch bar trucks
to shake themselves apart could be overcome with periodic
maintenance, but cars that ran in interchange might not be
returned to their owners for months or even years at a time,
and when off-line, their trucks seldom received any attention
apart from journal oiling.
As a result, though the venerable arch bar design remained the
de facto standard (1 and 2), late nineteenth and early twentieth
3
3: John J. Tatum, head of the Baltimore & Ohio car
department and a prolific innovator, designed this
improved arch bar truck in the early 1920s when arch
bars had fallen out of favor with most other railroads.
The spring seat and columns were a one-piece steel
casting and Barber lateral motion rollers were located
between the springs and the bolster.
Freight Car Trucks - 3
index contents
MRH-May 2013