Canadian National Railways
Steam Locomotive Roster
Numbers Qty Class Bldr Year Ø / Haulage Rating Notes =========== ==== ====== ====== ===== =================== ============= CNR 6165-6179 15 U-2-e MLW 1940 73 / 57% B
Locomotive Builder's Page.
Variable "D" is the cylinder size in inches, while "S" is the stroke in inches and "P" is the boiler pressure in P.S.I. For a locomotive like 6167, the formula works out to:
Which, when rounded up, is the locomotive's haulage rating (57,000 Lbs = 57%)
The haulage rating was often rounded to the closest percent. Some haulage ratings were not an accurate reflection of the locomotive's tractive effort, as some haulage ratings were standardized between groups of locomotives. As well, if the engine was modified, through boiler pressure, driver size or cylinder size, the haulage rating would change, but not always.
A number of engines were equipped with booster engines. These engines were identified by having a "B" next to the haulage rating. Initially, CNR practice was to mark the tractive effort with the booster engaged next to the tractive effort without the booster. A booster engine is normally located on the trailing truck, or on one of the tender trucks and could add roughly an additional 10,000 Lbs of tractive effort when starting.
Lastly, when diesels started to appear, CN applied the haulage rating concept to its diesel fleet. Diesels can be rated in two ways, Starting Tractive Effort and Continuous Tractive Effort. Intially CN choose to use the Starting Tractive Effort as its haulage rating for diesels.
My 1947 Motive Power Analysis lists the tractive effort for the CNR fleet (at that time). What really shocked me when reading the document, was the fact that an ALCo S2 is listed as developing 60,000 lbs. of Tractive Effort (60%) which is more then my Northern! After a little sleuthing, I realized what was going on, and after checking an edition of the CNR Diesel Unit Data book, I learned that the Continuous Tractive Effort rating on an S2 was only 34,000 lbs (34%). CN eventually realized that Contiunous Tractive effort was a more useful figure and began using that figure. Early diesels did in fact have the Starting Tractive Effort (expressed as a haulage rating) listed on the side of the cab, for exaple 60% for an NW2, but this was later revised. Given how convoluted the issue was, I choose not to list the Tractive Efforts for Diesels in that report.
After studying photographs in my collection it seems that by 1949 CN decided to rate Diesels by their Continuous Tractive Effort. However in the 50's CN adopted a new classification scheme for its Diesels that displayed horsepower, and judging by photos, I suspect this new scheme was introduced in 1954 when CN revamped its image and adopted the Maple Leaf Monogram.
Etc.Several abbreviations will appear from time to time throughout the roster. Their meanings are stated below:
R/b - Rebuilt
Railroad History #147, published by the Locomotive & Railway Historical Society 1982.
Canadian National Steam Power, by Anthony Clegg & Ray Corley, published by Trains & Trolleys 1969.
CN Lines Magazine, Published by the CN Lines SIG, see also CN Lines Datapack #1.
Canadian National In The East Vol 1-3, by J.Norman Lowe, published by British Railway Modellers of North America 1981-1985.
A Photo History Of The Prince Edward Island Railway, by Allen Graham, Published by Williams & Crue Fine Printing 2000.
Canadian National Railways Mechanical Department, Steam Locomotive Diagrams.