| Union Pacific Big Boy | |
|---|---|
| Big Boy #4014 on display in Pomona, CA | |
| Power type | Steam |
| Reference:[1] | |
| Builder | American Locomotive Company |
| Build date | 1941 (20), 1944 (5) |
| Total produced | 25 |
| Configuration | 4-8-8-4 |
| UIC classification | (2′D)D2′ h4 |
| Gauge | 4 ft 8 1⁄2 in (1,435 mm) |
| Leading wheel diameter |
36 in (914 mm) |
| Driver diameter | 68 in (1,727 mm) |
| Trailing wheel diameter |
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) |
| Weight on drivers | 540,000 lb (244,939.9 kilograms) |
| Locomotive weight | 762,000 lb (345,637.4 kilograms) |
| Tender weight | 342,200 lb (155,219.3 kilograms) (2/3 load) |
| Locomotive & tender combined weight |
1,250,000 lb (566,990.5 kilograms) |
| Fuel type | Coal |
| Fuel capacity | 30 short tons (27.2 t) |
| Water capacity | 22,000 US gal (83,000 l; 18,000 imp gal) |
| Boiler | 95 in (2,400 mm) |
| Boiler pressure | 300 lbf/in² (2.1 MPa) |
| Firegrate area | 150 sq ft (14 m2) |
| Heating surface: Tubes and flues |
5,035 sq ft (468 m2) |
| Heating surface: Firebox |
720 sq ft (67 m2) |
| Heating surface: Total |
5,735 sq ft (533 m2) |
| Superheater type | Type A |
| Superheater area | 2,043 sq ft (190 m2) |
| Cylinders | Four |
| Cylinder size | 23.75 × 32 in (603 × 813 mm) |
| Top speed | 80 mph (130 km/h) |
| Tractive effort | 135,375 lbf (602.18 kN) |
| Factor of adhesion |
4.11 |
| Career | 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 | Eight preserved, remainder scrapped. |
Big Boy was the name of the Union Pacific Railroad's 4000-class 4-8-8-4 articulated steam locomotives, built between 1941 and 1944 by American Locomotive Company (Alco). The 25 Big Boys were the only locomotives to have the 4-8-8-4 wheel arrangement, which combined two sets of eight driving wheels with a four-wheel leading truck for stability entering curves and a four-wheel trailing truck to support the large firebox.
Contents |
The Union Pacific Railroad (UP) introduced the Challenger-type (4-6-6-4) locomotives in 1936 on its main line across Wyoming. For most of the way, the maximum grade is 0.82% in either direction, but the climb eastward from Ogden, Utah, into the Wasatch Range (Wahsatch, on the railroad) reached 1.14%. Hauling a 3,600-short ton (3,300 t) freight train demanded doubleheading and helper operations, and adding and removing the helper engines from a train slowed operations down.
One answer: design a new locomotive. But for such locomotives to be worthwhile, they had to be faster and more powerful than slow mountain luggers like the 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 sustained speed—60 miles per hour (100 km/h)—once past the mountain grades.
Led by Otto Jabelmann, the UP's design team, in collaboration with Alco, re-examined the Challengers, which were designed by A.H. Fetters. They found that the goals could be achieved by making several changes to the Challenger design, including increasing the firebox to about 235 by 96 inches (6.0 × 2.4 m) (about 155 sq ft/14.4 m2), lengthening the boiler, adding four driving wheels and reducing the size of the driving wheels from 69 to 68 in (1.753 to 1.727 m).
The Big Boy are articulated, per the Mallet locomotive design, but used simple (single) rather than double expansion. They were designed for stability at 60 miles per hour (100 km/h). They were built with a heavy margin of reliability and safety, as they normally operated well below that speed in freight service. Peak horsepower was reached at about 35 mph (56 km/h); optimal tractive effort, at about 10 mph (16 km/h).
Twenty-five Big Boys were built, in two groups of ten and one of five. All were coal burning, with large grates to burn low-quality Wyoming coal from mines owned by the railroad. One locomotive, #4005, was experimentally converted to oil. Unlike a similar experience with the Challenger types, this was not successful, and the locomotive was soon changed back to coal. The cited reason for this failure was the use of a single burner, which, with the Big Boy's large firebox, created unsatisfactory and uneven heating. It is unknown why multiple burners were not employed, though with dieselization in full swing after 1945 the company probably lost interest in further development of steam.
Postwar increases in the price of both coal and labor and the efficiency of diesel-electric motive power foretold a limited life for the Big Boys, but they were among the last steam locomotives taken out of service. Towards the end of the 4000's career (in the late 1950s) it was found that they could still pull more than their rated tonnage of 3,600 tons (3,300 t). Their ratings were increased several times until they regularly pulled 4,450 short tons (4,040 t) up the Wasatch grade, unassisted.
The last revenue train hauled by a Big Boy ended its run early in the morning on July 21, 1959. Most were stored operational until 1961, and four remained in operational condition at Green River, Wyoming until 1962. Their duties were assumed by diesels and turbines.
The Big Boy is well-represented among preserved steam locomotives in the United States. Eight of the 25 still exist:
All except numbers 4005 and 4017 are in the open without protection from the elements. The dry air of Southern California has helped #4014 to remain well preserved, assisted by care of the local chapter of the Railway and Locomotive Historical Society. The Steamtown example is also said to be in good condition, though the harsher weather of the northeast has taken its toll. The Forney Museum of Transportation in Denver moved the 4005 to a renovated building in January 2001. Thanks to considerable fundraising and volunteer efforts, number 4017 now resides with other pieces of railroad equipment in a climate-controlled shed at the museum in Green Bay. Number 4023 is the only known Big Boy to move by highway since preservation, to the new Kenefick Park in Omaha. Number 4018 is planned to be moved to a new location north of Dallas in Frisco, Texas.
There are no operable Big Boys and no plans to return any to running condition.
William W. Kratville, Big Boy, Omaha: Kratville Publications, 1972.
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