6-wheel truck classes
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?
On Sep 17, 2010, at 9:11 AM, al.kresse wrote:
Does anyone have early Master Car Builder's or ARA documentation explaining the rationale for 4-wheel vs. 6-wheel trucked freight car classes?Al,
If I understand your question correctly, ultimately, car tonnage ratings depend on axle and bearing ratings (and car construction that can withstand the load).
From an email in 2006 by Tim Gilbert:
Between 1925 and 1962, the Maximum Total Weight Allowed on the RailAs noted, the numbers apply to 2 4-wheel trucks. To get the number for each axle, divide by 4. Thus, a car would require 10 "A" axles to achieve the rating of car with 4 "D" axles. The ratings increases you site appear to come from both increasing the number and the diameter of the axles.
Bruce F. Smith
"Some days you are the bug, some days you are the windshield."
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