^[2][3] 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 .

Quick Facts Canadian National U-1-a and U-1-b, Type and origin ...

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 (0.87 m) Driver dia. 73 in (1.9 m) Trailing dia. 43 in (1.1 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:[1]

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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.^[4]

U-1-a 6004 was 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"^[5]

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.