Cubic Capacity Confusion

Kurt Laughlin <fleeta@...>

I'm compiling a list of the "most common" boxcars for my layout and decided to use the recapitulation lists for each RR in the ORER as a start for finding total quantities for a particular road. I'm a bit puzzled by the rather varied interpretation of cubic capacity values. For example, I see listings for 3712, 3713, 3715, 3716, and 3719 cu ft XMs which appear to all be 40-6 x 9-2 x 10-0 AAR cars. Also, from the RPC 8 article on 10-0 IH XMs, B&O 285000 is 3715, CRP 22057 is 3713, CRP 22501 is 3712, C&O 14111 is 3713. Why the variation? If I fix the length and height at the nominal values then each inch of width accounts for 33-3/4 cu ft, so to get a 1 cu ft difference means a change of about 1/32 of an inch in width or height or a hair over 1/8 inch in length. Were they really measuring or calculating things that closely? Is there a standard procedure for calculating cubic capacity?

Another oddity is that the volume numbers painted on cars do not always match the numbers in the ORER. Some examples: NYC 109445 - marked 2956, listed as 2955. From the RPC 8 article mentioned above, SP 102199 is marked 3782 cu ft, ORER lists it as 3783. I could understand a mistake in repainting, but the SP pics are builder's photos.


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