The Union Pacific Big Boy is a type of simple articulated 4-8-8-4 steam locomotive manufactured by the American Locomotive Company (ALCO) between 1941 and 1944 and operated by the Union Pacific Railroad in revenue service until 1962.

As outlined in Locobase 8339, these 4-8-4s were the premier passenger power on the Union Pacific. When the UP returned to the Alco in 1939 for more of these enormous locomotives, the builder supplied these fifteen with a Type E superheater installation with …

The Union Pacific FEF series consists of 45 4-8-4 "Northern" steam locomotives built by the American Locomotive Company (ALCO) between 1937 and 1944 and operated by the Union Pacific Railroad until 1959. Like the other Union Pacific steam classes, the acronym comes from the first letter of the spelling of its wheel arrangement: Four Eight Four.

A 4-8-8-4 in the Whyte notation for the classification of steam locomotives by wheel arrangement, is a locomotive with a four-wheel leading truck, two sets of eight driving wheels, and a four-wheel trailing truck.

The 4-8-4 was the ultimate wheel configuration for the modern passenger and fast freight steam locomotive. The eight driver arrangement was usable on almost every main line in North America and with drivers up to 80 inches in diameter allowed …

During the late 1930s, the Union Pacific often used helpers to move trains from Ogden to Wahsatch. The UP wanted to simplify this move so they asked their "Department of Research and Mechanical Standards" (DoRMS) to design a locomotive that could pull a 3600 ton train unassisted over the 1.14% grade of the Wahsatch.

2016年12月20日 · The Big Boy utilized a 4-8-8-4 wheel arrangement and was the only locomotive to do so. At the front of the engine was a four-wheel leading truck that had 36 in (.91 m) wheels. This was followed by eight 68 in (1.73 m) drive wheels, with a single piston driving a set of four wheels on each side of the engine.

2025年2月25日 · Few steam locomotives compare to Union Pacific's (UP) colossus 4-8-8-4 "Big Boy." It was designed during the zenith of seam technology and earned celebrity status as soon as the first debuted in 1941.

2024年4月2日 · Big Boys - UP 4-8-8-4's The 4-8-8-4 wheel arrangment was unique to both the United States and to the Union Pacific Railroad. No other railroad and no other country made locomotives anything like these. Many consider the 4-8-8-4s or "Big Boys" to be the largest steam locomotives ever built in the entire world. It would be hard to argue differently.

The FEF-1 4-8-4s were the first steam locomotives in the UP fleet to have a boiler rated to operate at 300 pounds per square inch. That meant they were exceptionally powerful machines. The new locomotives also featured cast-steel frames with cast air pump supports, crosshead guide supports, back cylinder heads, main air reservoirs, spring brake ...