A Mallet locomotive is a type of compound articulated steam locomotive, invented by the Swiss engineer Anatole Mallet (1837–1919).
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.
The Whyte notation is a classification method for steam locomotives, and some internal combustion locomotives and electric locomotives, by wheel arrangement. It was devised by Frederick Methvan Whyte, and came into use in the early twentieth century following a December 1900 editorial in American Engineer and Railroad Journal.
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. Only one model of locomotives has ever used this configuration, and that is commonly known as "Union Pacific Big Boys" after the railroad that operated them.
The UIC classification of locomotive axle arrangements, sometimes known as the German classification or German system, describes the wheel arrangement of locomotives, multiple units and trams. It is used in much of the world, notable exceptions being the United Kingdom, which uses a slightly simplified form of UIC, and in North America, where the AAR wheel arrangement system is used to describe diesel and electric locomotives. In North America, the Whyte notation is only used for steam locomotives.
Under the Whyte notation for the classification of steam locomotives, 2-10-2 represents the wheel arrangement of two leading wheels, ten powered and coupled driving wheels, and two trailing wheels. In the United States and elsewhere the 2-10-2 is known as the Santa Fe type, after the Atchison, Topeka and Santa Fe Railway that first used the type in 1903.
A 2-8-8-2, in the Whyte notation for describing steam locomotive wheel arrangements, is an articulated locomotive with a two-wheel leading truck, two sets of eight driving wheels, and a two-wheel trailing truck. The equivalent UIC classification is, refined to Mallet locomotives, (1'D)D1'. These locomotives usually employ the Mallet principles of articulation—with the rear engine rigidly attached to the boiler and the front engine free to rotate—and compounding. The 2-8-8-2 was a design largely limited to American locomotive builders. The last 2-8-8-2 was retired in 1962 from the N&W's roster, two years past the ending of steam though steam was still used on steel mill lines and other railroads until 1983.
Under the Whyte notation for the classification of steam locomotives by wheel arrangement, a 2-6-6-2 is a locomotive with one pair of unpowered leading wheels, followed by two sets of three pairs of powered driving wheels and one pair of trailing wheels. The wheel arrangement was principally used on Mallet-type articulated locomotives, although some tank locomotive examples were also built. A Garratt locomotive or Golwé locomotive with the same wheel arrangement is designated 2-6-0+0-6-2 since both engine units are pivoting.
The Union Pacific Railroad 9000 Class was a class of 88 steam locomotives, built by ALCO for the Union Pacific between 1926 and 1930.
In Whyte notation, 2-4-4-2 refers to a railroad steam locomotive that has two leading wheels followed by four coupled driving wheels, a second set of four coupled driving wheels, and two trailing wheels.
Under the Whyte notation for the classification of steam locomotives by wheel arrangement, 4-10-2 represents the arrangement of four leading wheels, ten powered and coupled driving wheels and two trailing wheels. In South Africa, where the wheel arrangement was first used, the type was known as a Reid Tenwheeler. In the United States of America it was known as a Southern Pacific on the Southern Pacific Railroad and as an Overland on the Union Pacific Railroad.
Union Pacific 844 is a class "FEF-3" 4-8-4 "Northern" type steam locomotive owned and operated by the Union Pacific Railroad for its heritage fleet. Built in December 1944 by the American Locomotive Company (ALCO) of Schenectady, New York, No. 844 is one of four surviving FEF series locomotives and the only one in operation.
Union Pacific 3985 is a four-cylinder simple articulated 4-6-6-4 "Challenger"-type steam locomotive built in July 1943 by the American Locomotive Company (ALCO) of Schenectady, New York, for the Union Pacific Railroad. No. 3985 is one of only two Challengers still in existence and the only one to have operated in excursion service.
The Union Pacific Challengers are a type of simple articulated 4-6-6-4 steam locomotive built by American Locomotive Company (ALCO) from 1936 to 1944 and operated by the Union Pacific Railroad until the late 1950s.
Union Pacific 6936 is an EMD DDA40X locomotive built for the Union Pacific Railroad (UP). Previously a part of UP's heritage fleet, 6936 was for several decades the last remaining operational "Centennial" type, and thus the largest operational diesel-electric locomotive in the world. It is now owned by the Railroading Heritage of Midwest America in Silvis, Illinois, who plans to return the locomotive to operation.
In Whyte notation, a 4-6-6-2 is a steam locomotive with four leading wheels in an unpowered bogie at the front of the locomotive followed by two sets of driving wheels with six wheels each, followed by two unpowered trailing wheels at the rear of the locomotive.
In the Whyte notation for describing steam locomotive wheel arrangement, a 2-6-6 is a locomotive with a two-wheeled leading truck, six driving wheels, and a six-wheeled trailing truck. All the locomotives produced of this arrangement have been tank locomotives, and the vast majority in the United States. It was a popular arrangement for the larger Mason Bogies, as well as some of the largest suburban tank locomotives.
Union Pacific 4014 is a steam locomotive owned and operated by the Union Pacific (UP) as part of its heritage fleet. It is a four-cylinder simple articulated 4-8-8-4 "Big Boy" type built in 1941 by the American Locomotive Company (ALCO) at its Schenectady Locomotive Works. It was assigned to haul heavy freight trains in the Wasatch mountain range. The locomotive was retired from revenue service in 1959 and was donated to the Railway & Locomotive Historical Society; thereafter, it was displayed in Fairplex at the RailGiants Train Museum in Pomona, California.
The Union Pacific heritage fleet includes commemorative and historic equipment owned by the Union Pacific Railroad. The fleet currently consists of two historic steam locomotives, three historic diesel locomotives, seventeen modern diesel locomotives in historic or commemorative paint schemes and nearly four dozen passenger cars used on office car specials and excursion trains.
Union Pacific 5511 is a 2-10-2 “Santa Fe” type steam locomotive built by the Baldwin Locomotive Works in 1923 as part of the Union Pacific Railroad's TTT-6 class. It is the last remaining member of its class and the only remaining 2-10-2 to be operated by the Union Pacific.
