Under the Whyte notation for the classification of steam locomotives, 0-2-2-0 represents the wheel arrangement of no leading wheels, four powered but uncoupled driving wheels on two axles, and no trailing wheels. [1] Some authorities place brackets around the duplicated but uncoupled wheels, creating a notation 0-(2-2)-0. [2]
The first recorded usage of the arrangement was in four locomotives designed by Patrick Stirling for the Glasgow and South Western Railway in 1855. [2] The design was not successful and the locomotives were withdrawn by 1867. It would later be used on the Royal Bavarian State Railways ML 2/2 class of 1906, which were much more numerous and successful.
The Mount Washington Cog Railway has eight 0-2-2-0's and only two are in working order, with three in storage and the remainder on display.
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 locomotives, 0-4-0 represents one of the simplest possible types, that with two axles and four coupled wheels, all of which are driven. The wheels on the earliest four-coupled locomotives were connected by a single gear wheel, but from 1825 the wheels were usually connected with coupling rods to form a single driven set.
Under the Whyte notation for the classification of steam locomotives, 2-2-0 represents the wheel arrangement of two leading wheels on one axle, two powered driving wheels on one axle, and no trailing wheels. This configuration, which became very popular during the 1830s, was commonly called the Planet type after the first locomotive, Robert Stephenson's Planet of 1830.
Under the Whyte notation for the classification of steam locomotives, 4-2-2 represents the wheel arrangement of four leading wheels on two axles, two powered driving wheels on one axle, and two trailing wheels on one axle.
Under the Whyte notation for the classification of steam locomotives, a 2-6-4 locomotive has two leading wheels, six coupled driving wheels and four trailing wheels.
Under the Whyte notation for the classification of steam locomotives, 2-4-2 represents the wheel arrangement of two leading wheels on one axle, four powered and coupled driving wheels on two axles and two trailing wheels on one axle. The type is sometimes named Columbia after a Baldwin 2-4-2 locomotive was showcased at the 1893 World's Columbian Exposition held at Chicago, Illinois.
An 0-2-2, in the Whyte notation for the classification of steam locomotives by wheel arrangement, is one that has two coupled driving wheels followed by two trailing wheels, with no leading wheels. The configuration was briefly built by Robert Stephenson and Company for the Liverpool and Manchester Railway.
Under the Whyte notation for the classification of steam locomotives, 2-4-0 represents the wheel arrangement of two leading wheels on one axle, four powered and coupled driving wheels on two axles and no trailing wheels. In most of North America it became known as a Porter.
Under the Whyte notation for the classification of steam locomotives, 0-4-4 represents the wheel arrangement of no leading wheels, four powered and coupled driving wheels on two axles, and four trailing wheels on two axles. This type was only used for tank locomotives.
The AA20 was a one-off steam locomotive constructed by the Soviet Union.
Under the Whyte notation for the classification of steam locomotives, 0-2-4 represents the wheel arrangement of no leading wheels, two powered driving wheels on one axle, and four trailing wheels on two axles.
Under the Whyte notation for the classification of steam locomotives, 0-6-0+0-6-0 represents the wheel arrangement of an articulated locomotive with two separate swivelling engine units, each unit with no leading wheels, six powered and coupled driving wheels on three axles and no trailing wheels. The arrangement is effectively two 0-6-0 locomotives operating back-to-back and was used on Garratt, Double Fairlie, Meyer and Kitson-Meyer articulated locomotives. A similar arrangement exists for Mallet steam locomotives on which only the front engine unit swivels, but these are referred to as 0-6-6-0.
A compound locomotive is a steam locomotive which is powered by a compound engine, a type of steam engine where steam is expanded in two or more stages. The locomotive was only one application of compounding. Two and three stages were used in ships, for example.
Under the Whyte notation for the classification of steam locomotives, 2-2-2-0 usually represents the wheel arrangement of two leading wheels on one axle, four powered but uncoupled driving wheels on two axles, and no trailing wheels, but can also be used to represent two sets of leading wheels two driving wheels, and no trailing wheels. Some authorities place brackets around the duplicated but uncoupled wheels, creating a notation 2-(2-2)-0, or (2-2)-2-0, as a means of differentiating between them. Others simply refer to the locomotives 2-2-2-0.
The leading wheel or leading axle or pilot wheel of a steam locomotive is an unpowered wheel or axle located in front of the driving wheels. The axle or axles of the leading wheels are normally located on a leading truck. Leading wheels are used to help the locomotive negotiate curves and to support the front portion of the boiler.
Under the Whyte notation for the classification of steam locomotives, 2-2-2-2 could represent either the wheel arrangement of two leading wheels, four powered but uncoupled driving wheels, and two trailing wheels; or of two independent leading axles, two driving wheels, and two trailing wheels.
Under the Whyte notation for the classification of steam locomotives, 2-2-4-0T represents the wheel arrangement of two leading wheels on one axle, two driving wheels powered from the inside cylinders, four coupled driving wheels powered from the outside cylinders but no trailing wheels.
Under the Whyte notation for the classification of steam locomotives, 4-2-2-0 represents the wheel arrangement of four leading wheels on two axles, four independently driven driving wheels on two axles, and no trailing wheels. The arrangement became known as double single.
The Z21 class was a class of steam locomotives built for the New South Wales Government Railways in Australia.
Under the Whyte notation for the classification of steam locomotive wheel arrangements, a 4-4-6-2 is a locomotive with two pairs of leading wheels, one set of four driving wheels, a second set of six driving wheels, and a pair of trailing wheels.