Tonnage Ratings and Weather Reductions for Locomotives

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Probably another reason was the difficulty of getting air through a longer train.  As temperature dropped, air connections tended to be less secure, as in the gaskets between air hoses in the “glad hand’' between the cars – that old bugaboo called “leakage” reared its ugly head.  The power brake law required the air pressure on the caboose to be within fifteen pounds of the feed valve setting on the locomotive, and on really long trains it might take an hour or so of pumping up to get the pressure on the caboose; this was necessary before the brake test could be made and leakage had to be within prescribed limits.  Several yards had “yard air” which could be coupled up to an outbound track of cars to charge up the brakes; there was even a device called a “time o test” (if I recall) which could make the brake test and check leakage on a track of cars.

Hope this is not TMI . . .

Ed King

From: NW Mailing List 
Sent: Saturday, December 15, 2018 8:36 PM
To: nw-mailing-list at nwhs.org 
Subject: Tonnage Ratings and Weather Reductions for Locomotives

By time-table instructions train tonnage in the steam era was reduced as ambient temperatures fell. Reductions were as much as 25% at temperatures below 0 degrees F (Rating G).

 

Were there multiple reasons for this reduction? Was the primary reason the increased rolling resistance of cars with friction bearings? Were other factors involved?

 

Thanks,  John Garner,  Newport VA 



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