Tonnage Ratings and Weather Reductions for Locomotives

NW Mailing List nw-mailing-list at
Wed Dec 26 20:55:31 EST 2018

This first-hand account is informative with a humorous element as well. Railroading ultimately comes down to people and their personalities. And that’s good.


“Cold Trains Move Hard”

“Trains move easier in warm weather than they do when it is cold. This is probably because oil has a tendency to thicken up when it gets cold. Some paraffin based oils of cheaper grades will get as thick as Vaseline when it is thirty degrees below zero. A one hundred-car train would have eight hundred bearings, and a little difference in a bearing’s friction would make a big difference in the way a train moved. In Crestline [OH] we never needed help getting eastbound trains out of the yards, but once during a prolonged cold spell of sub-zero weather they had to use pusher engines.

I was firing for engineman Leo Zink, and we had an eastbound freight train of one hundred cars and 10,000 tons gross weight to go to Conway, Pennsylvania. Our engine was a new Q2, four cylinder 4-4-6-4. It could handle the train but would need pusher engines on the grades. Leo made four tries at starting the train but was unable to get it moving. The Q2 locomotive wanted to move the train, and the train wanted to stay put, and we began to wonder which one would have its way. We took slack for our fifth try. This time we activated our booster engine on the trailing wheels under the cab, which increased our tractive force to 115,800 pounds. We moved slowly forward, and when all the slack was taken up, we moved a foot or so. The train quivered, and at this point you can feel the stretch in a train. I was sitting on the edge of the fireman’s seat and discovered that I was hunching like a kid does when he’s trying to start his wagon down a hill. I laughed at myself for my action.  Then  I looked at the engineman, and he was hunching the same way I was. We both had a good laugh. Who knows, maybe it was our hunching that got our ten thousand-ton train started on its eastward journey.”


Paul C. Dietz, Fireman PRR 1943-1947


>From a terrific read . . . Firing on the Pennsy. Gateway Press, Inc. 2001


John Garner, Newport VA


From: NW Mailing List [mailto:nw-mailing-list at] 
Sent: Tuesday, December 25, 2018 11:01 PM
To: NW Mailing List <nw-mailing-list at>
Subject: Re: Tonnage Ratings and Weather Reductions for Locomotives


Just as an addendum, we know cold weather affected journal bearings. They were harder to get rolling in the cold. Extra power could get a train started at normal tonnage in the yards, but a stop out on the division in cold weather might mean that it could not be restarted. 


Sent from my iPhone

On Dec 25, 2018, at 4:00 PM, NW Mailing List <nw-mailing-list at <mailto:nw-mailing-list at> > wrote:

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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