Tonnage Ratings and Weather Reductions for Locomotives

NW Mailing List nw-mailing-list at
Wed Dec 26 21:20:48 EST 2018



I hoped you would chime in on this. I did look in Pokey ETT thru 1963. Tonnage reduction charts continued to be included. So as you say it was not a function of steam or diesel (or electric). I suspect it was more a function of friction bearings. Whether these charts (or ETT) were adhered to or not is another matter. Operating management at some point obviously thought tonnage reduction was important. It would be interesting to see when the temperature charts switched from being tonnage based to being train length based.


Merry Christmas indeed.


John Garner


From: NW Mailing List [mailto:nw-mailing-list at] 
Sent: Tuesday, December 25, 2018 6:00 PM
To: nw-mailing-list at
Subject: Re: Tonnage Ratings and Weather Reductions for Locomotives


Hello John,

I think the table heading may be a bit misleading, leaning on a correlation between train tonnage and length, and implying the loco was affected. 

The normal tonnage rating was a function of the loco and applied to the train weight, but the weather reduction was a function of ambient temperature and applied to the train length, apparently.  The same percentage reduction applied to steam and diesel, suggesting steam was not a factor.

Not that it mattered--the tables seemed to be ignored by Pocahontas Div train crews.

>From the engineer's perspective, locomotive performance did not seem to be affected by low temperatures (steam or electric). Stiff journals might account for the derating, but again, had no significant affect on train handling when combined with other factors. Understand that enginemen were informed (by the conductor) of train length, not tonnage.

>From the conductor's perspective, they figured tonnage and adjusted it (based on experience and depending on the job) for all manner of variables, including weather conditions, engine class, individual engine, individual engineer, load level, even wet leaves, and weeds, in at least one case. Low temperatures alone did not seem to be a substantial factor.

Cold temps did raise concern for brakes, train line length and getting enough air to the rear for a full release. If not, they would get permission to set over twenty cars and try again. A frozen line was common and brakemen would carry a flask of "antifreeze" in their pocket to pour in the hose of the first car.

Busy recently, but enjoy catching up on the List.

Merry Christmas to All,
Grant Carpenter

On 12/15/2018 7:36 PM, NW Mailing List wrote:

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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