Union Pacific 4012

Specifications
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)

Type and origin
Type and origin
Power type	Steam
Builder	American Locomotive Company
Serial number	69583
Build date	November 1941

Union Pacific 4012
Union Pacific 4012
	"Big Boy" 4012 on static display at Steamtown National Historic Site, August 2023
Power type
Type and origin
Power type	Steam
Builder	American Locomotive Company
Serial number	69583
Build date	November 1941
Configuration:;
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)
Maximum speed
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
Operators
Career
Operators	Union Pacific Railroad
Class	4884-1
Numbers	4012
First run	1941
Last run	1959
Retired	1962
Restored	May 5, 2021 (cosmetically)
Disposition	On static display at Steamtown National Historic Site Scranton, PA

Union Pacific 4012 is one of eight preserved Union Pacific Big Boy locomotives. Built in November 1941 by the American Locomotive Company (ALCO) 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.