6-wheel truck classes

al.kresse <water.kresse@...>

Does anyone have early Master Car Builder's or ARA documentation explaining the rationale for 4-wheel vs. 6-wheel trucked freight car classes?

Example: circa 1915-1920, 50-ton axle 4-wheel trucks become 100-ton 6-wheel (used for USRA class gon designs) and not (50+25) 75-ton trucks; and 70-ton axle 4-wheel trucks become 120-ton 6-wheel trucks and not (70+35) 105-ton trucks.

I believe there were only 40-, 50-, and 70-ton "standards" for cast sideframe truck designs but a full range of axle "standards" for this era.

Did the use of clasp brakes give "rationale" to classify on the upside or the journal-size ratings? Was this was before tested DIN life ratings were associated with bearing sizes and types?

Al Kresse
Romeo, Michigan

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