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20th century were of 40, 50, or 70 tons nominal capacity, and
most of what follows will be devoted to trucks of those capaci-
ties. Truck capacity was stated in terms of how much weight
a pair of trucks would support. Thus a single "50-ton" truck
was designed to carry only 25 tons, with the other half of the
50 tons resting on the truck at the opposite end of the car.
Capacity was determined by the size of the journals, as follows:
40 tons nominal capacity, 5" X 9" journals, load limit 136000 lbs.
50 tons nominal capacity, 5-1/2" X 10" journals, load limit
169000 lbs.
70 tons nominal capacity, 6" X 11" journals, load limit 210000 lbs.
Nominal capacities were intended to indicate approximately
how much weight could be loaded into or on the car, so load
limits were more than half again higher than nominal capaci-
ties to account for the empty weight of the car itself.
1
1: A turn-of-the-century arch bar truck with straight
lower chords, cast steel bolster, and steel channel
spring plank. The vertical columns on either side of the
bolster were also steel castings.
Freight Car Trucks - 2
index contents
MRH-May 2013