CN U-1-a and U-1-b

The Canadian National U-1-a U-1-b class locomotives were three subclasses of 37 4-8-2 Mountain-type steam locomotives built for the Canadian National Railways between 1923 and 1924. They were retired between 1951 and 1962 .

Canadian National U-1-a and U-1-b
CN U-1-a locomotive 6015; On public display at Jasper, Alberta, since July 1972
Type and origin Power type Steam Builder Canadian Locomotive Company Build date 1923–1924 Total produced 16 (U-1-a) 21 (U-1-b) Rebuild date 1947 (1) Number rebuilt 1 (No. 6001)
Specifications Configuration: ​  • Whyte 4-8-2  • UIC 2′D1′ h2 Gauge 4 ft 8+1⁄2 in (1,435 mm) Leading dia. 34+1⁄4 in (0.870 m) Driver dia. 73 in (1.854 m) Trailing dia. 43 in (1.092 m) Minimum curve 16° Wheelbase Loco: 41 ft 9 in (12.73 m) Length 90 ft 4+1⁄4 in (27.540 m) Width 10 ft 9+5⁄8 in (3.292 m) Adhesive weight 233,790–235,390 lb (106.05–106.77 tonnes) Loco weight 355,570–355,570 lb (161.28–161.28 tonnes) Total weight 602,600–603,870 lb (273.33–273.91 tonnes) Fuel type Coal or oil Fuel capacity Coal: 17–20 long tons (17–20 t) Oil: 4,000–5,000 imp gal (18,200–22,700 L; 4,800–6,000 US gal) Water cap. 9,500–10,000 imp gal (43,000–45,000 L; 11,400–12,000 US gal) Firebox: ​  • Grate area 66.7 sq ft (6.20 m2) Boiler pressure 210 lbf/in2 (1.4 MPa) Heating surface: ​  • Firebox 319 sq ft (29.6 m2)  • Tubes and flues 3,730 sq ft (347 m2)  • Total surface 4,049 sq ft (376.2 m2) Superheater: ​  • Type Schmidt  • Heating area 810–1,087 sq ft (75.3–101.0 m2) Cylinders Two, outside Cylinder size 26 in × 30 in (0.66 m × 0.76 m) Valve gear Walschaerts Train heating Steam heat Loco brake Independent air Train brakes Automatic air
Performance figures Maximum speed 75–95 mph (121–153 km/h) Tractive effort 49,590 lbf (220.6 kN) Factor of adh. 4.71 – 4.74
Career Operators Canadian National Railways Power class 50% Number in class 16 (U-1-a) 21 (U-1-b) Numbers 6000–6015 (U-1-a) 6016-6036 (U-1-b) Retired 1950 (6004) 1951-1962 Preserved 6015 Disposition 6015 preserved remainder scrapped
References for above:

Table of Orders and numbers

Year	Subclass	Quantity	Manufacturer	Serial nos.	CN Nos.	Notes
1923	U-1-a	16	Canadian Locomotive Company	1696–1711	6000–6015	6015 preserved in Jasper, Alberta, since 1972
1924	U-1-b	21	Canadian Locomotive Company	1744–1758, 1764–1769	6016–6036	All scrapped

Accidents and incidents

On 1 September 1947, locomotive 6001 was involved in the Dugald rail accident. It collided with another CN 4-8-2 numbered 6046. No. 6001 was later rebuilt by CN.

On 21 November 1950, locomotive 6004 was severely damaged a head-on collision with S-2-a 2-8-2 No. 3538 at Canoe River, British Columbia. It was scrapped in June 1951 (as was the 3538). There was a gap of four years before the next U-1-a or U-1-b went: two were scrapped in 1955, four in 1957, six in 1958, six in 1959, eight in 1960, seven in 1961, and the last two, 6000 and 6001 in 1962.

In art

U-1-a 6004 is the subject of a 1924 publicity poster by C. Norwich. It depicts the locomotive speeding along in the foreground, while in the background is a pine-covered, snow-capped mountain peak. Across the top is the "Canadian National Railways" logotype; across the bottom are the words, "Across Canada", and in the lower left, above the artist name and date is "The Continental Limited in the Canadian Rockies"

Preservation

One locomotive has been preserved:

• CN 6015 (U-1-a) — Retired 1960; to CHRA, Delson, Quebec. On public display in Jasper, Alberta, since July 1972.