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{{Merge from|4-8-8-4|discuss=Talk:4-8-8-4|date=January 2010}}
{{Infobox Locomotive
{{Infobox Locomotive
|name = Union Pacific ''Big Boy''
|name = Union Pacific ''Big Boy''

Revision as of 16:20, 30 July 2011

Union Pacific Big Boy
Big Boy #4014 on display in Pomona, CA
Type and origin
Reference:[1]
Power typeSteam
BuilderAmerican Locomotive Company
Build date1941 (20), 1944 (5)
Total produced25
Specifications
Configuration:
​
 • Whyte4-8-8-4
 • UIC(2′D)D2′ h4
Gauge4 ft 8+1⁄2 in (1,435 mm)
Leading dia.36 in (914 mm)
Driver dia.68 in (1,727 mm)
Trailing dia.42 in (1,067 mm)
Wheelbase72 ft 5.5 in (22.09 m)
LengthLocomotive: 85 ft 3.4 in (25.99 m)
Overall: 132 ft 9+1⁄4 in (40.47 m)
Width11 ft (3.4 m)
Height16 ft 2+1⁄2 in (4.94 m)
Adhesive weight540,000 lb (244,939.9 kilograms)
Loco weight762,000 lb (345,637.4 kilograms)
Tender weight342,200 lb (155,219.3 kilograms) (2/3 load)
Total weight1,250,000 lb (566,990.5 kilograms)
Fuel typeCoal
Fuel capacity30 short tons (27.2 t)
Water cap.22,000 U.S. gal (83,000 L; 18,000 imp gal)
Firebox:​
 • Grate area150 sq ft (14 m2)
Boiler95 in (2,400 mm)
Boiler pressure300 lbf/in2 (2.1 MPa)
Heating surface:​
 • Firebox720 sq ft (67 m2)
 • Tubes and flues5,035 sq ft (468 m2)
 • Total surface5,735 sq ft (533 m2)
Superheater:
​
 • TypeType A
 • Heating area2,043 sq ft (190 m2)
CylindersFour
Cylinder size23.75 in × 32 in (603 mm × 813 mm)
Performance figures
Tractive effort135,375 lbf (602.18 kN)
Factor of adh.4.11
Career
Last runJuly 21, 1959
Preserved4004, 4005, 4006, 4012, 4014, 4017, 4018, 4023
DispositionEight preserved, remainder scrapped.


Big Boy was the name given to the Union Pacific Railroad's twenty-five 4000 class 4-8-8-4 articulated steam locomotives built between 1941 and 1944 by Alco.

Background

The Union Pacific Railroad introduced the Challenger-type (4-6-6-4) locomotives in 1936 on its main line across Wyoming. For most of the distance the maximum grade is 0.82% in either direction, but the climb eastward from Ogden, Utah up the Wasatch grade (Wahsatch, on the railroad) is 1.14%, demanding a locomotive with greater tractive effort and horsepower to eliminate doubleheading and helper operations. In collaboration with the American Locomotive Company, the UP's design team, headed by Otto Jabelmann, re-examined the original Challengers designed by A.H. Fetters. They found that by increasing the firebox to approximately 235 by 96 inches (6.0 m × 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), they could achieve that goal.

History

The Big Boys were the only locomotives to have the 4-8-8-4 wheel arrangement, combining 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.

The Big Boys were designed to pull a 3,600 short ton (3,300 t) freight train over the long 1.14% grade of the Wasatch Mountains in Utah. Before their arrival, helpers were needed. Adding and removing helpers from a train slowed them down. 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 Union Pacific ("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. 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.

They are articulated, per the Mallet locomotive design, but used simple (single) rather than double expansion, unlike the original Mallet design.

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).

25 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 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. 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.

Preservation

The Big Boy is well represented among preserved steam locomotives in the United States. Eight of the 25 still exist:

Big Boy #4023 on permanent display in Omaha, Nebraska

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, NE. 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.

The backhead (controls) of 4017 at the National Railroad Museum in Green Bay, WI

References

  1. ^ C.B. Peck, ed. (1950). 1950-52 Locomotive Cyclopedia of American Practice. New York: Simmons-Boardman. pp. 501, 519, 523, 545.

William W. Kratville, Big Boy, Omaha: Kratville Publications, 1972.

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