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(60-62 continued) the 20th century, the ASF, Lewis, and
Lamont trucks, all designed for 100-ton coal hoppers
and gondolas. None were produced in large numbers.
62
In the 1920s, a small number of high-capacity flat cars began
to be built to carry very heavy industrial loads, and these cars
also required special heavy duty trucks. Cars of 90 tons nominal
capacity usually had four-wheel trucks (63 and 64). Cars with 100
ton or higher capacities used six-wheel trucks (65 and 66). In a
few extreme cases, two four-wheel trucks connected by a mas-
sive span bolster were used at each end of the car (67).
Early roller bearing trucks
Roller bearing trucks existed earlier than many modelers real-
ize; the Stafford Roller Bearing Car-Truck Corporation intro-
duced a roller bearing arch bar truck in the early 1920s (68).
Those early roller bearings were costly and did not wear well,
61
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