Union Pacific 4012

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Union Pacific 4012
"Big Boy" 4012 on static display at Steamtown National Historic Site, August 2023
Type and origin Power type Steam Builder American Locomotive Company (Schenectady Works) Serial number 69583 Build date November 1941
Specifications Configuration: ​  • Whyte 4-8-8-4  • UIC (2′D)D2′ h4 Gauge 4 ft 8+1⁄2 in (1,435 mm) Leading dia. 36 in (914 mm) Driver dia. 68 inches (170 cm) Trailing dia. 42 in (1,067 mm) Minimum curve 288 ft (88 m) radius/ 20° Wheelbase Locomotive: 72 ft 5.5 in (22.09 m) Overall: 117 ft 7 in (35.84 m) Length Locomotive: 85 ft 7.8 in (26.11 m) Overall: 132 ft 9+7⁄8 in (40.48 m) Width 11 ft (3.4 m) Height 16 ft 2+1⁄2 in (4.94 m) Axle load 67,500 lb (30,617 kilograms) Adhesive weight 540,000 lb (244,940 kilograms) Loco weight 762,000 lb (345,637 kilograms) Tender weight 342,200 lb (155,219 kilograms) (2/3 load) Total weight 1,250,000 lb (566,990 kilograms) Tender type 25-C Fuel type Coal Water cap. 24,000 US gal (91,000 L; 20,000 imp gal) Firebox: ​  • Grate area 150 sq ft (14 m2) Boiler 95 in (2,400 mm) Boiler pressure 300 lbf/in2 (2.1 MPa) Heating surface: ​  • Firebox 704 sq ft (65 m2)  • Tubes and flues 5,185 sq ft (482 m2)  • Total surface 5,889 sq ft (547 m2) Superheater: ​  • Type Type E  • Heating area 2,466 sq ft (229 m2) Cylinders 4 Cylinder size 23.75 in × 32 in (603 mm × 813 mm)
Performance figures Maximum speed 80 mph (130 km/h) Power output 5,300–7,000 hp (4,000–5,200 kW) @ 41 mph Tractive effort 135,375 lbf (602.18 kN) Factor of adh. 3.99
Career Operators Union Pacific Railroad Class 4884-1 Numbers UP 4012 First run 1941 Last run 1959 Retired 1962 Restored May 5, 2021 (cosmetically) Disposition On static display

Union Pacific 4012 is a 4884-1 class 4-8-8-4 "Big Boy" type steam locomotive, one of eight preserved Union Pacific Big Boy locomotives. Built in November 1941 by the American Locomotive Company (ALCO) at its Schenectady Locomotive Works of Schenectady, New York, No. 4012 was retired in 1962 and donated to Steamtown, U.S.A, in Bellows Falls, Vermont, and later moved to Steamtown National Historic Site in Scranton, Pennsylvania, where it remains today.