The Union Pacific 4-8-8-4 “Big Boy” Steam Locomotive

The Union Pacific 4-8-8-4 “Big Boy” Steam Locomotive

Welcome to another installment of Prototype Profile! This month it is prototype profile: the Union Pacific 4-8-8-4 “Big Boy” steam locomotive. During the era of steam on the Union Pacific, getting heavy freight trains over the Wasatch Mountains between Ogden, Utah and Green River, Wyoming was a frustrating task. Union Pacific tried ever larger and more powerful steam locomotives to perform the duty, but even their mighty 4-6-6-4 Challenger type locomotives were not capable of doing the task alone. Sometimes they required a “double-header” to pull the train – that is, two locomotives working in tandem at the front of the train. Sometimes they required a helper shoving on the end of the train, and often with a double-header up front.

UP 4-6-6-4 Challenger #3985 at Alton, Iowa in 2008. Photo by Mark Evans. This file is licensed under the Creative Commons Attribution 2.0 Generic license.

In the late 1930s, UP’s Department of Research and Mechanical Standards began working with the American Locomotive Company (Alco, for short) on the design of their largest and most powerful locomotive. To achieve the goal of pulling a 3,600-ton train over the Wasatch without assistance and also be capable of sustained speeds of 60 miles per hour once past the steep 1.14% grade for eastbound trains, the new locomotive needed to have two sets of eight wheel drivers. For stability entering curves at the required speed, it needed a four-wheel leading truck. To support the heavy firebox, it needed another four-wheel truck under the cab. This resulted in a 4-8-8-4 wheel configuration in the Whyte notation of classifying steam locomotives.

UP 4-8-8-4 “Big Boy” #4019 in Echo Canyon, Utah on an unknown date. Unknown photographer. This work is in the public domain because it was published in the United States between 1923 and 1977 and without a copyright notice.

Alco officially termed the design the “Class 4000”, the Union Pacific intended to name it the “Wasatch class”. According to legend, an unknown employee at Alco scrawled the words “Big Boy” on one of the monster locomotives under construction, and the name stuck for everyone.

Union Pacific was the only railroad to own and operate the Big Boy. The locomotives arrived in two distinct groups. The first group of 20, dubbed “Class 1” by UP, were built starting in 1941. World War II interrupted the production of the Big Boys so the second group, dubbed “Class 2” by UP, were built and delivered in 1944.

UP Big Boy #4000 in 1941. This is probably an official builders photo. Photographer unknown. This work is in the public domain because it was published in the United States between 1923 and 1977 and without a copyright notice.

The Big Boys lived up to expectations, and then some. The design had called for sustained speeds of 60 mph once over the mountains, but the Big Boys could actually achieve 80 mph (though they very rarely went over the 60 mph that was desired). They could produce 6,290 horsepower at 35 mph and they regularly pulled trains as heavy as 7,917 tons over the mountains without assistance. The Big Boy was a true marvel of engineering, design, and railroading.

Unfortunately, the Big Boys came along at a time when diesel-electric locomotives were on the rise. The last revenue freight pulled by a Big Boy was in July 1959. Diesel-electrics and experimental gas turbine engines were capable of performing the same feats as the Big Boy and doing it more inexpensively. The locomotives were stored operational for a few years, but the last one was finally retired in 1962. Thus ended the short-lived but legendary Big Boy locomotive.

UP Big Boy #4022 beside UP gas turbine-electic #75 at Cheyenne, Wyoming in November 1956. Photo by Doug Wornom. This work is in the public domain because it was published in the United States between 1923 and 1977 and without a copyright notice.

Most of the retired Big Boys were scrapped, but seven managed to survive in various museums and parks around the country. In July 2013, Union Pacific reacquired Big Boy #4014 from the Fairplex Rail Giants Museum in Pomona, California, adding to their roster of operational steam locomotives used for excursions and office car specials, joining FEF-3 “Northern” 4-8-4 #844 and “Challenger” 4-6-6-4 #3985. The Big Boy was moved by special train to UP’s Cheyenne, Wyoming shops where it would undergo full restoration to working order and once again steam under its own power to pull excursion trains. As of February 2017, #4014 has been completely disassembled and the shop began manufacturing new parts. Once that is complete, reassembly will take place.

UP Big Boy #4014 on display at Pomona Fairplex, Pomona, California before being reacquired by Union Pacific. Unknown photographer. This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

I hope you have enjoyed reading this month’s Prototype Profile: The Union Pacific 4-8-8-4 “Big Boy” Steam Locomotive. Join us next time for a look at railroading in Brazil!

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Robert Thomson

Robert W. Thomson is a life-long railfan, the son of a former L&N Railroad B&B gang foreman, and an amateur photographer. He was born and raised in southeast Tennessee but now lives in Butte, Montana with his wife, Connie and cat, Charlie. Robert has worked as a park ranger, underground mine tour guide, freelance roleplaying game writer, and ran his own roleplaying game publishing company until selling it in 2012.

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