Re: Cubic Capacity Confusion


Anthony Thompson <thompson@...>
 

Kurt Laughlin wrote:
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?
My understanding from talking to a railroad employee who was responsible for submitting material for ORER issues is that there was some latitude allowed in how the railroad chose to round off (or not round off) dimensional measurements. It is accordingly not surprising that entries vary.

Another oddity is that the volume numbers painted on cars do not always match the numbers in the ORER.
A railroad did not have to letter in accord with the ORER; and different parts of the company (different departments) were responsible for the two sets of data. Certainly it's true that the SP, with which I'm most familiar, had ORER entries at odds with its own freight car lettering.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
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