Railroads have specific tonnage ratings for each type of locomotive they operate over specific track segments. Each routing on a division has its own grades and profile of those grades.
Since I was in Dispatching the last 18 years of my career, I became intimately familiar with the tonnage ratings for each of the subdivisions of my territories.
One thing I NEVER came across was tonnage ratings for Steam Engine across the same territories I had current diesel ratings for.
I suspect current ‘road’ power has a significant advantage in both tons and speeds in the tonnage they are able to move, but I haven’t come across any steam engine tonnage ratings.
Video’s I have seen of steam loaded to the maximum on grades would indicate that steam was moving in the neighborhood of 5 MPH when loaded to the max. Diesels (DC) start getting into ‘short time’ ratings at speeds below about 12 MPH when operating with maximum exertion.
Don’t know if this will display correctly - CSX Baltimore Div. Ratings from late 1990’s - covers power from the few remaining Gen 2 diesels through the AC44’s and AC60’s -
Origin Dest MP MP
CUMBOY BRUNSY BA 105 BA 76 3950 4500 6000 7150 7800 9900 10500 11400
CUMBOY CUMBED BA 105 BA 178 4600 5250 7000 8300 9100 11550 12250 13300
MILLR1 CUMBOY BA 115 BA 105 2900 3300 4400 5200 5700 7250 7700 8350
NORBRN MILLR1 BA 177 BA 115 9900 11250 15000 17850 19500 24750 26250 28500
Employee timetables during the steam years on the N&W gave tonnage ratings for each type of steam locomotive.
One thing that I found interesting was that NOT UNTIL the advent of the AC diesel units could one diesel outpull an N&W Y6 class steam locomotive!
That may be true but through the wonder of multiple unit control, you could easily assemble the number of GP9’s under one throtttle that it would take to outpull the Y6b.
Train make up and any tonnage restrictions are defined in the carriers Operating Plan. Tonnage considerations apply from Origin to Destination and the maximum ruling grade between the two.
On CSX this plan was changed on a weekly basis to accomodate planned MofW curfews for major MofW projects (Rail Gangs, Tie & Surfacing Gangs, Curve Patch Gangs etc.)
Temperature considerations are implemented during cold weather with the length of trains being restricted account trainline leakage from cold air hose gaskets.
Building trains at A, they have no idea of wind conditions if any at Z. Observation from the CSX territory between Willard and Chicago - headwind is fine - a quartering head wind can suck 10 MPH out of a Intermodal train’s top speed.
Routine rain and snow don’t matter. When rainfall and snowfall is reported in inches per hour then it becomes an issue. Monsoon/Hurricanes & Blizzards are taken seriously.
Here you go Balt!
The following is from the Shenandoah Div. ETT effective July 21, 1955. The ruling grade can be as steep as 1.75% heading north and 1.80% heading south.
The following is for the same Shen. Div. in 1973. Note at this time there were plenty of GP9’s and RS11’s on the roster. Also note how the unit’s tonnage ratings were grouped as either four axle or six axle units.
On page 18 you see that Y5/Y6s were allowed 4650 tons on the climb from Walton to Christiansburg, which is six miles of 0.9 to 1.0%. Couple years later the rating increased to 5150 tons, so the usual coal train became 10300 tons with a Y at each end.
In 1958 Y5/Y6s were allowed 3600 tons on the 1.4% Elkhorn climb while GP9/RS11s were supposed to be good for 1400 tons (page 13)
But most RRs didn’t include ratings in the timetable. And, of course, we don’t know how fast the RR expected each engine to haul its rating, or how reliably.
Temperature differences reducing tonnage on the steam engines is interesting. Is the engine losing power OR is it an admission that cold oil in journal boxes is making it harder to pull the cars at the lower temperatures. Of course in today’s railroads we are dealing exclusively with roller bearings on all cars and engines.
Is steam being fed to the tender to keep the water from freezing? N&W used canteens with a lot of the articulated engines - was water in the canteen also heated sufficient to keep it from freezing?
Some railroads did away with the tonnage ratings by class of engine and just went by horsepower and a horsepower per trailing ton rating for the train type or general area. Another rating system is “equivalent powered axles” and “trailing tons per axle”.
As in the animal world, not all horses have the same power - thoroughbreds vs. Clydesdales. They are all horses but don’t have the same power or speed potential.
