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).
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.
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.
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, a 4-8-8-2 is a locomotive with four leading wheels, two sets of eight driving wheels, and a two-wheel trailing truck.
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 2-8-8-8-2 has two leading wheels, three sets of eight driving wheels, and two trailing wheels. Because of its length, such a locomotive must be an articulated locomotive. It is not longer than a normal articulated; the third set of drivers is located under the tender. All of the examples produced were a Triplex of the Mallet type.
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.
A 2-6-8-0 steam locomotive, in the Whyte notation for describing locomotive wheel arrangements, has two leading wheels, a set of six driving wheels, a set of eight driving wheels, and no trailing wheels. These locomotives usually employ the Mallet principle of articulation, with a swinging front engine and a rigidly attached rear engine.
A Meyer locomotive is a type of articulated locomotive. The design was never as popular as the Garratt or Mallet locomotives. It can be best regarded as 19th Century competition for the early compound Mallet and also the Fairlie articulated designs. Most single cab modern trains are of a similar design such as power cars, freight diesel locomotives, and some passenger locomotives.
A triplex Mallet locomotive is a steam locomotive that divides 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 Rhaetian Railway G 2/2+2/3, was a two-member class of metre gauge Mallet-type steam tank locomotives manufactured by SLM in Winterthur, Switzerland, in 1896, and operated until 1926 by the Rhaetian Railway, in the Canton of Graubünden, Switzerland.
The Rhaetian Railway G 2/3+2/2 was an eight member class of metre gauge Mallet-type steam locomotives manufactured by SLM in Winterthur, Switzerland in 1902, and operated until 1920–1921 by the Rhaetian Railway, in the Canton of Graubünden, Switzerland.
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 MB 2-6-6-0 of 1910 was a steam locomotive from the pre-Union era in the Colony of Natal.
The South African Railways Class MC 2-6-6-0 of 1912 was a steam locomotive.
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.
A multiplex locomotive is a steam locomotive that divides the driving force on its wheels by using multiple pairs of cylinders to drive multiple driving wheel set groups. Such a locomotive will necessarily articulated if it has more than two sets of driving wheels. There were locomotive projects with three, four, five or six sets of drive wheels. However, these locomotives were never built, except for four triplex locomotives in the United States and one quadruplex locomotive in Belgium.
