Car capacity vs load limit, was Late 40's to mid 50's military rail movements

Bruce Smith


Excellent question! Here's what that data on the side of a car means. 

CAPY (or capacity) is the nominal weight allowed by the truck bearings, axles, and of course, car construction. On the F30A that is listed as 140,000 lbs or 70 tons.

Lt. Wt. (or light weight) is obviously the empty weight of the car (or tare weight). That is important as many shipments are charged by weight so you have to know what the car weighs so as not to charge for that.

Ld. Lmt. (or load limit) is the actual weight allowed for the load. This is determined by subtracting the Lt Wt from the total allowed weight on the rail (in this case) for a car with 6" x 11" journals, which is 210,000 lbs. The exception to this are cars where the Ld Lmt has a star in front of it, indicating a structural restriction on the weight of the load to less than that allowed by the truck bearings (the star actually indicates to anyone reweighing the car not to use the mathematical formal I've given to calculate Ld Lmt.)

This confusion comes about because railroads wanted an easy system to classify capacity, (40, 50, 55, 70 ton, etc...) but it is really the total weight on the rails that matters for the given bearing size. 

When a car is reweighed, the number determined is the Lt. Wt. If that changes, then the Ld Lmt has to change by a corresponding amount. The Capy does not change. That's why, when showing reweigh data as freshly painted on weathered cars, I often only protect the last 3 digits of the Lt Wt and Ld Lmt and I always make sure that they add up to the correct total for that capacity car.

Thus, my comment that the load limit on the PRR F30A is around 158,000 lbs, well within the ability to carry a 60 ton tank or even a 65 ton tank. 

Bruce Smith
Auburn, AL

From: <> on behalf of spsalso via <Edwardsutorik@...>
Sent: Monday, October 18, 2021 10:48 PM
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Subject: Re: [EXT] Re: [RealSTMFC] Late 40's to mid 50's military rail movements

The capacity of the car in the photo reads 140000 pounds.  Can you crowd that up to 158000 pounds?

The T43 was reported to weigh 60 tons in the New York Times, back in the day.  It was also reported to weigh 50 tons.  In the New York Times.

Wikipedia says an M103 weighs 65 tons.

Military things generally weighing a bit more than hoped, I will lean towards the T43 being a heavy tank.

Anyway, it clearly arrived at its destination.


Edward Sutorik

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