Canadian National / Grand Trunk Western 4-8-4 Locomotives in Canada

Class U-2a/b (Locobase 240)

Data from tables in 1930 Locomotive Cyclopedia; "4-8-4 Locomotive for the Canadian National Railways", Engineering, (23 March 1928), pp. 347-348, Plate XXXVII [37] on 354-355 and (20 April 19280, pp. 473-474. See also articles in Rail Canada, No 487 (May-June 2002), pp. 43-73. (Thanks to Chris Hohl for sending a PDF of the Rail Canada articles.)

These locomotives were the first in a large series of 4-8-4s of very similar design that totalled more than 200 engines.

Firebox had water tubes that contributed 100 sq ft (9.3 sq m) to the direct heating surface; the boiler had an Elesco K29 feedwater heater. Of the 177 flues, 15 did not contain superheater elements. Firebox heating surface area included the combustion chamber, 22 sq ft (2 sq m) of arch tubes and 95 sq ft (8.8 sq m) of thermic syphons. Main frames were made of vanadium steel for the 6105, 6110, 6112, 6114-6129. The others--6104, 6106-6109, 6111, 6115, 6130-6139--had main frames made of nickel steel

U-2a (works #1800-1819) numbered from 6100 to 6119 and delivered from Canadian Loco Works in 1927.

U-2b (6120-6139), delivered from Montreal in 1927 (works #67351-67370), identical except for 233,400-lb weight on drivers and commensurate 4.10 factor of adhesion. Also the first ring of the boiler measured 80 7/8" in diameter.

6100 was named Confederation and that moniker was used in preference to "Northern" on all CNR 4-8-4s.

GTW had several batches of identical locomotives in the U-3 class; see Locobases 3171 and 255.

Class U-2c/d/e/f (Locobase 2951)

Data from 1930 Locomotive Cyclopedia and CN to 1953 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also articles in Rail Canada, No 487 (May-June 2002), pp. 43-73. (Thanks to Chris Hohl for sending a PDF of the Rail Canada articles. And thanks to Larry Walton for reporting the mismatch between the road numbers and the class size quantity.)

Firebox had thermic syphons and water tubes that contributed 100 sq ft (9.3 sq m) to the direct heating surface. The boiler had feedwater heater. These were follow-ons to the U-2a/2b with a different tube/flue ratio. All of the engines had Boxpok drivers and nickel-steel main frames.

Obviously, the CNR found the dimensions of this design to be a good fit as they added locomotives to the class for eleven years. All of the U-2s had the trailing axles that somewhat unusually carried wheels of considerably different sizes. The leading wheels were 34 1/4" (876 mm) in diameter, while the rear wheels measured 48" (1,219 mm). All the truck wheels rolled on SKF roller bearings.

MLW's works # for the 6140-6159 were 67769-67788 in 1929. Seven years later, the company added 5 more (works #68710-68714) built to the same specs, but weighing a bit more (237,600 lb on the drivers, 390,000 lb total). In 1940, MLW supplied works #69260-69274 as road numbers 6165-6179 and Canadian Locomotive Works added 10 more (works #1960-1969) as road numbers 6180-6189.

Class U-2g/h "War Babies" (Locobase 241)

Data from 1947 Locomotive Cyclopedia and CN to 1953 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also articles in Rail Canada, No 487 (May-June 2002), pp. 43-73. (Thanks to Chris Hohl for sending a PDF of the Rail Canada articles.) U-2g 6200-6234 -works 69698-69722, 69780-69799 in 1943; U-2h 6235-6259 -- works numbers 70303-70332 in 1943-1944.

As World War II increased traffic demands of all kinds, the CN went back to Montreal to buy an additional 65 Northerns to run all over the CN system from Montreal to Halifax, NS pulling fast freights and express passenger traffic. Their birth dates" inspire the nickname "war baby" Northerns.

Firebox heating surface included 99 sq ft (9.3 sq m) of thermic syphons (three), boiler had type E superheater. It was a slight redesign of the earlier U-2 classes (Locobase 2951 ) that traded some tube heating surface for superheater area. Like the earlier classes, the trailing axles somewhat unusually carried wheels of considerably different sizes. The leading wheels were 34 1/4" (870 mm) in diameter, while the rear wheels measured 48"(1,219 mm).

Class U-3a (Locobase 3171)

Data from 1947 Locomotive Cyclopedia and CN to 1953 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also articles in Rail Canada, No 487 (May-June 2002), pp. 43-73. (Thanks to Chris Hohl for sending a PDF of the Rail Canada articles.) Alco works numbers were 67339-67350 in 1927.

Firebox had thermic syphons and arch tubes that contributed 100 sq ft (9.3 sq m) to the direct heating surface. These locomotives and their CNR U-2 cousins were relatively light 4-8-4s of relatively orthodox layout for the late 1920s. See Locobase 255 for the later U-3cs, which were quite different in their internal layout.

Like the U-2s, the trailing truck wheel diameters differed considerably. In the case of the U-3s, the leading carrying truck under the firebox measured 33" (838 mm) in diameter while the trailing wheels were 10" (254 mm) larger.

Class U-3b (Locobase 255)

Data from 1947 Locomotive Cyclopedia and CN to 1953 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also John B Corns, "6325--A New Face in the World of Steam" Trains, November 2001, downloaded from [] (link no longer active).

Firebox had 95 sq ft (8.8 sq m) of thermic syphons. These locomotives and their CNR U-2 cousins were relatively light 4-8-4s. Like all CNR Northerns, the trailing axles somewhat unusually carried wheels of considerably different sizes. The leading wheels were 34 1/4" (870 mm) in diameter, while the rear wheels measured 48" (1,219 mm).

The U-3bs (works #69618-69642) had been preceded by a 1927 batch of U-3a, which is the subject of a separate entry (Locobase 3171). As they were very nearly the same size and tractive power, comparing the two directly reveals the impact of the superpower revolution on how that power was generated. The tube-flue ratio changes profoundly from 200+ small-diameter tubes and 50 flues of more than twice the cross-sectional area to a reversed layout of tubes and flues that are nearer the same size. The firebox heating surface actually declined, but the superheating percentage climbed seven points to more than 30% of the combined heating surface.

[] by John B. Corns details the refurbishment of this locomotive for operations on the Ohio Central beginning in September 2001. The article sketches how well-suited for its service was this design. As passenger engines, they wheeled 16-car trains across the relatively flat Michigan rail at impressive speeds. One U-3b reportedly hit 106.5 mph (171 kph) pulling 12 cars in 1956. Corns notes that the class was "equally at ease heading 80-car manifests across GTW's Chicago Division ..."

Among the features in this design were roller bearings on all but the driving axles, Boxpok drivers, Nicholson thermic syphons, and Elesco exhaust steam injectors ("the 'poor man's feedwater heaters'").

Restoration to tourist operation by owner Jerry Jacobson is estimated to have cost him over 3/4 of a million dollars.

Class U-4a (Locobase 242)

Data from 1947 Locomotive Cyclopedia and the CN to 1953 locomotive diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also "Canadian National Railways-Giant Locomotive", Engineer, Volume 163 (15 January 1937), pp. 73-74; and articles in Rail Canada, No 487 (May-June 2002), pp. 43-73. (Thanks to Chris Hohl for sending a PDF of the Rail Canada articles.) Works numbers were 68715-68719 in June 1936.

Said to be a streamlined variant of the U-2 series; see in particular the detailed sketch of all the different tweaks used to accomplish streamlining on page 74 of the Canadian Rail account. Differences are more than skin-deep, however, and include a smaller boiler and grate, larger drivers, lower adhesive weight, and lower tractive effort. The firebox included two thermic syphons that contributed 83 sq ft (7.71 sq m) and two arch tubes that added another 15 sq ft (1.39 sq m) to firebox heating surface area, the engines had Boxpok drivers and roller bearings on all of the engine and tender trucks.

Seven more went to the Grand Trunk Western as #6405-6411; see Locobase 243. (For some reason, the GTWs had one less small tube.)

Class U-4b (Locobase 243)

Data from 1947 Locomotive Cyclopedia and the CN to 1953 locomotive diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. (Thanks to Chris Hohl for his 8 November 2019 email noting the original coal capacity and tender weight.) Lima's works numbers were 7759-7764 in 1938.

Very slight differences between these engines and the CNR U-4s numbered 6400-6404 (Locobase 242). Note the light average axle loading and the weight per foot of driving wheelbase. Direct heating surface area included a combustion chamber and thermic syphons. Piston valves measured a relatively small 12" (305 mm) in diameter.

Chris Hohl notes that when delivered, the U-4s trailed tenders weighing 270,500 lb (122.697 kg)) and carrying 16 short tons (14.5 metric tons) of coal.