Union Pacific Big Boy

Union Pacific Big Boy

Union Pacific Big Boy #4019 hauling a freight train in Echo Canyon, Utah.

Type and origin Reference: Power type Steam Builder American Locomotive Company Build date 1941 (20), 1944 (5) Total produced 25

Specifications Configuration 4-8-8-4 UIC class (2′D)D2′ h4 Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Leading dia. 36 in (914 mm) Driver dia. 68 in (1,727 mm) Trailing dia. 42 in (1,067 mm) Wheelbase 72 ft 5.5 in (22.09 m) Length Locomotive: 85 ft 3.4 in (25.99 m) Overall: 132 ft 9 1⁄4 in (40.47 m) Width 11 ft (3.4 m) Height 16 ft 2 1⁄2 in (4.94 m) Axle load 67,800 lb (30,800 kg) Adhesive weight 540,000 lb (245,000 kg) Loco weight 762,000 lb (345,600 kg) (381t) Tender weight 342,200 lb (155,220 kg) (2/3 load) Total weight 1,250,000 lb (567,000 kg) Fuel type Coal Fuel capacity 28 short tons (25.4 t; 25.0 long tons) Water cap 25,000 US gal (95,000 l; 21,000 imp gal) Firebox:  • Firegrate area 150 sq ft (14 m2) Boiler 95 in (2,400 mm) Boiler pressure 300 lbf/in2 (2.1 MPa) Heating surface 5,735 sq ft (533 m2)  • Tubes and flues 5,035 sq ft (468 m2)  • Firebox 720 sq ft (67 m2) Superheater: ​  • Type Type A  • Heating area 2,043 sq ft (190 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 6,290 hp (4,690 kW) @ 35 mph Tractive effort 135,375 lbf (602.18 kN) Factor of adh. 3.99

Career Operators Union Pacific Railroad Class 4000–4019: 4884-1 4020–4024: 4884-2 Last run July 21, 1959 Preserved 4004, 4005, 4006, 4012, 4014, 4017, 4018, 4023 Disposition 17 scrapped 7 preserved for display 1 undergoing restoration to operating condition (4014)

Cost to build US$ 265,000 in 1941, equivalent to $4,314,943 in 2016

Big Boy is the popular name of the American Locomotive Company 4000-class 4-8-8-4 articulated, coal-fired, steam locomotives manufactured between 1941 and 1944 and operated by the Union Pacific Railroad until 1959.

The Big Boy fleet of twenty five locomotives were used primarily in the Wyoming Division to haul freight over the Wasatch mountains between Green River, Wyoming and Ogden, Utah. They were the only locomotives to use a 4-8-8-4 wheel arrangement consisting of a four-wheel leading truck for stability entering curves, two sets of eight driving wheels and a four-wheel trailing truck to support the large firebox.

According to a Union Pacific executive, the 4-8-8-4 series originally was to have been called "Wasatch". One day while one of the engines was being built an unknown worker scrawled "Big Boy" in chalk on its front. With that, the legendary name was born and has stuck ever since.

Union Pacific introduced the Challenger-type (4-6-6-4) locomotives in 1936 on its main line over the Wasatch Range between Green River, Wyoming and Ogden, Utah. For most of the route, the maximum grade is 0.82% in either direction, but the climb eastward from Ogden, Utah into the Wasatch Range reached 1.14%. Hauling a 3,600-short-ton (3,300 t; 3,200-long-ton) freight train demanded double heading and helper operations, and adding and removing helper engines slowed operations.

To eliminate the need for double heading and helper operations, Union Pacific decided to design a new locomotive. For such a locomotive to be worthwhile, it would have to be faster and more powerful than slower locomotives like earlier compound 2-8-8-0s that UP tried after World War I. To avoid locomotive changes, the new class would need to pull long trains at a sustained speed of 60 miles per hour (100 km/h) once past mountain grades. In fact, it was designed so that it could travel smoothly and safely at 80 miles per hour (130 km/h) — even though it was not intended to be used that fast.