Class U-2a/b (Locobase 240)

Data from tables in 1930 Locomotive Cyclopedia.

Firebox had water tubes that contributed 100 sq ft to the direct heating surface; the boiler had feedwater heater. U-2a (works #1800-1819) numbered from 6100 to 6119 and delivered from Canadian Loco Works in 1927.

U-2b (6120-6150), 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 collection.

Firebox had thermic syphons and water tubes that contributed 100 sq ft 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.

Obviously, the CNR found the dimensions of this design to be a good fit as they added locomotives to the class for 11 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" in diameter, while the rear wheels measured 48".

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 (Locobase 241)

Data from 1947 Locomotive Cyclopedia and CN to 1953 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

Firebox heating surface included 99 sq ft of thermic syphons (3), 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" in diameter, while the rear wheels measured 48".

U-2g 6200-6234 (works #69698-69722, 69780-69799) in 1943.

U-2h 6235-6259. (70303-70332) in 1943-1944.

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 collection.

Firebox had thermic syphons and arch tubes that contributed 100 sq ft to the direct heating surface. These locomotives (Alco works #67339-67350) 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" in diameter while the trailing wheels were 10" larger.

Class U-3c (Locobase 255)

Data from 1947 Locomotive Cyclopedia and CN to 1953 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

Firebox had 95 sq ft 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" in diameter, while the rear wheels measured 48".

The U-3cs (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, it's instructive to examine 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 7 points to more than 30% of the combined heating surface.

www.ohiocentralrr.com/shop/johnb.html 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 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-4 (Locobase 242)

Data from 1947 Locomotive Cyclopedia and the CN to 1953 locomotive diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

Said to be a streamlined variant of the U-2 series. Works numbers were 68715-68719. 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 thermic syphons.

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-4 (Locobase 243)

Data from 1947 Locomotive Cyclopedia and the CN to 1953 locomotive diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

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. Lima's works numbers were 7759-7764.