A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material to heat water in the locomotive's boiler to the point where it becomes gaseous and its volume increases 1,700 times. Functionally, it is a steam engine on wheels.
A Mallet locomotive is a type of compound articulated steam locomotive, invented by the Swiss engineer Anatole Mallet (1837–1919).
A 2-8-8-4 steam locomotive, under the Whyte notation, has two leading wheels, two sets of eight driving wheels, and a four-wheel trailing truck. The type was generally named the Yellowstone, a name given it by the first owner, the Northern Pacific Railway, whose lines ran near Yellowstone National Park. Seventy-two Yellowstone-type locomotives were built for four U.S. railroads.
Main components found on a typical steam locomotive include:
An articulated locomotive is a steam locomotive with one or more engine units that can move independently of the main frame. Articulation allows the operation of locomotives that would otherwise be too large to negotiate a railroad's curves, whether mainlines or special lines with extreme curvature such as logging, industrial, or mountain railways.
Under the Whyte notation for the classification of steam locomotive wheel arrangements, a 2-10-10-2 is a locomotive with two leading wheels, two sets of ten driving wheels, and a pair of trailing wheels.
In the Whyte notation for the classification of steam locomotive wheel arrangement, a 2-6-6-4 is a locomotive with a two-wheel leading truck, two sets of six driving wheels, and a four-wheel trailing truck. All 2-6-6-4s are simple articulated locomotives.
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.
In the Whyte notation for the classification of steam locomotive wheel arrangement, an 0-4-4-0 is a locomotive with no leading wheels, two sets of four driving wheels, and no trailing wheels. The arrangement is chosen to give the articulation of a locomotive with only the short rigid wheelbase of an 0-4-0, but with its weight spread across eight wheels, and with all the weight carried on the driving wheels; effectively a flexible 0-8-0. Articulated examples were constructed as Mallet, Meyer, BMAG and Double Fairlie locomotives and also as geared locomotives such as Shay, Heisler, and Climax types. A similar configuration was used on some Garratt locomotives, but it is referred to as 0-4-0+0-4-0. In the electric and diesel eras, the Bo-Bo is comparable and closest to the Meyer arrangement of two swivelling bogies.
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.
Under the Whyte notation for the classification of steam locomotives, a 2-8-8-8-4 has two leading wheels, three sets of eight driving wheels, and four trailing wheels.
The term cab forward locomotive refers to various rail and road vehicle designs that place the driver's compartment substantially farther towards the front than is common practice.
Southern Pacific 4294 is a class "AC-12" 4-8-8-2 Cab forward type steam locomotive that was owned and operated by the Southern Pacific Railroad (SP). It was built by the Baldwin Locomotive Works in March 1944 and was used hauling SP's trains over the Sierra Nevada, often working on Donner Pass in California. Today it is preserved at the California State Railroad Museum (CSRM) in Sacramento, California.
The Royal Bavarian State Railways' sole class S 2/6 steam locomotive was built in 1906 by the firm of Maffei in Munich, Germany. It was of 4-4-4 wheel arrangement in the Whyte notation, or 2'B2' h4v in the UIC classification scheme, and was a 4-cylinder, von Borries, balanced compound locomotive. It was initially assigned No. 3201.
A triplex locomotive was a steam locomotive that divided the driving force on its wheels by using three pairs of cylinders to drive three sets of driving wheels. Any such locomotive will inevitably be articulated. All triplex locomotives built were of the Mallet type, but with an extra set of driving wheels under the tender. The concept was extended to locomotives with four, five or six sets of drive wheels. However, these locomotives were never built, except for one quadruplex locomotive in Belgium.
The South African Railways Class KM 0-6-0+0-6-0 of 1904 was an articulated steam locomotive from the pre-Union era in Transvaal Colony.
The South African Railways Class MA 2-6-6-0 of 1909 was a steam locomotive from the pre-Union era in the Natal Colony.
The South African Railways Class MD 2-6-6-2 of 1910 was a steam locomotive from the pre-Union era in Transvaal.
The South African Railways Class MG 2-6-6-2 of 1911 was a steam locomotive from the pre-Union era in Transvaal.
Under the Whyte notation for the classification of steam locomotives, a 2-8-8-8-8-2 has two leading wheels, four sets of eight driving wheels, and two trailing wheels. Because of its length, such a locomotive must be an multiplex locomotive. It is longer than a normal articulated locomotive; the fourth set of drivers is located under the tender.
