Under the Whyte notation for the classification of steam locomotives, 0-4-2 represents the wheel arrangement with no leading wheels, four powered and coupled driving wheels on two axles, and two trailing wheels on one axle. The configuration was often used for tank engines, which is noted by adding letters to the configuration, such as 0-4-2T for a conventional side-tank locomotive, 0-4-2ST for a saddle-tank locomotive, 0-4-2WT for a well-tank locomotive, and 0-4-2RT for a rack-equipped tank locomotive. In the 1880s and 1890s the type was also used for some famous tender locomotives.
Other equivalent classifications are:
- UIC classification: B1 (also known as German and Italian classifications)
- French classification: 021
- Turkish classification: 23
- Swiss classification: 2/3
The first locomotive built in Germany in 1838, the Saxonia, was also an 0-4-2. In the same year Todd, Kitson & Laird built two examples for the Liverpool and Manchester Railway, one of which, LMR 57 Lion, has been preserved.
Over the next quarter of a century the type was adopted by many early British railways for freight haulage since it afforded greater adhesion than the contemporary 2-2-2 passenger configuration, although in time they were also used for mixed traffic duties.
The Emperor Ferdinand Northern Railway (Kaiser Ferdinands-Nordbahn) acquired the locomotive "Ajax" and her sister engine "Minotaurus", built by Jones, Turner and Evans in 1841, to work the line between Vienna and Stockerau. The locomotive Ajax has been preserved at the Technisches Museum Wien since 1992 and is described as "the oldest preserved steam locomotive on the European continent.".
In Finland the 0-4-2 was represented by the Classes B1 and B2.
In 1905 the Nederlands Indische Spoorweg opened a line between Yogyakarta and Ambarawa via Magelang, a hilly region requiring a rack railway because of the 6.5% gradients. The 0-4-2T wood burning B25 class were made for this line in 1902 by Maschinenfabrik Esslingen, Germany. They were four cylinder compound locomotives with two of the cylinders working the pinion wheels.
There are two examples of B25 class locomotive still in operation, namely B25-02 and B25-03. Both were based in Ambarawa, where they have served for more than a hundred years. Locomotive B25-01 may also still be found at the entrance to the Ambarawa Railway Museum.
On the island of Sumatra, there are some larger cousins of this class being used for hauling coal trains, namely the D18 and E10 classes.
The 0-4-2T arrangement was used by two classes of locomotives operated by the New Zealand Railways Department. The first was the C class of 1873, originally built as an 0-4-0T. The class was found to be unstable at speeds higher than 15 mph, so by 1880 all members of the class had been converted to 0-4-2T to rectify this problem.
The second and more notable 0-4-2T class, and the only one actually built as 0-4-2T, was the unique H class designed to operate the Rimutaka Incline on the Wairarapa Line. The Incline's steep gradient necessitated the use of the Fell mountain railway system, and the six members of the H class spent their entire lives operating trains on the Incline. Except for a few brief experiments with other classes, the H class had exclusive use of the Incline from their introduction in 1875 until the Incline's closure in 1955. The class leader, H 199, is preserved on static display at the Fell Engine Museum in Featherston and is the only extant Fell locomotive in the world.
The 0-4-2T arrangement was also employed for steam locomotives operated by small private industrial railways and bush and mineral tramways. One such locomotive, built by Peckett and Sons in 1938, is currently operational on the Goldfields Railway that runs between Waihi and Waikino along a stretch of the former route of the East Coast Main Trunk Railway in the Bay of Plenty.
Although the type was not used by any major railroads in North America, H. K. Porter, Inc and the Baldwin Locomotive Works produced many small tank locomotives of this type for industrial and plantation work. The 0-4-2T Olomana built by Baldwin in 1883 is a famous example of such types.
In September 1859 Messrs. E. & J. Pickering, contractors to the Cape Town Railway and Dock Company for the construction of the Cape Town-Wellington railway line, imported a small 0-4-0 side-tank steam locomotive from England for use during the construction of the railway. This was the first locomotive in South Africa. In 1874 the locomotive was rebuilt to a 0-4-2T configuration before it was shipped to Port Alfred, where it served as construction locomotive on the banks of the Kowie river and was nicknamed ”Blackie”. It has been declared a heritage object and was plinthed in the main concourse of Cape Town station.
In 1860 the Cape Town Railway and Dock Company took delivery of eight standard gauge tender locomotives with a 0-4-2 wheel arrangement for service on the Cape Town-Wellington line, which was still under construction. They remained in service on this line while it was being converted to dual standard-and-Cape gauges from around 1872 and were only retired in 1881, when sufficient Cape gauge locomotives were in service.
Two 3 ft 6 in (1,067 mm) tank engine classes of this wheel arrangement were supplied to the Nederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij (NZASM) by Maschinenfabrik Esslingen and Breda, Nederland between 1890 and 1894.
The earlier class of twenty-four 19 Tonner locomotives, built by Maschinenfabrik Esslingen and Machinefabriek Breda v/h Backer & Rueb, were delivered between 1890 and 1892. Between 1906 and 1909, while in Central South African Railways (CSAR) service, ten of them were converted to rail motor engines for use on suburban services. This entailed being semi-permanently coupled to a passenger coach that contained a driving cab at the rear, with the controls arranged so that the push-pull unit could be driven from either vehicle. In 1912 these locomotives were taken onto the South African Railways (SAR) roster as obsolete unclassified locomotives.
The latter class of four 32 Tonner rack locomotives, built by Esslingen in 1894 and 1897, was equipped with pinions for use on the rack railway section between Waterval Onder and Waterval Boven in the eastern Transvaal. They survived through the Imperial Military Railways (IMR) and CSAR eras and, although the rack section was removed in 1908, they were still in service in 1912 when they were taken onto the SAR roster as obsolete unclassified locomotives.
Between 1897 and 1901 several 0-4-2ST saddle tank steam locomotives, built for 600 mm (1 ft 11 5⁄8 in) narrow gauge by Dickson Manufacturing Company of Scranton in Pennsylvania, were delivered to various gold mines on the Witwatersrand by Arthur Koppel, acting as importing agents. In 1915, when an urgent need arose for additional locomotives in Deutsch-Südwest-Afrika (now Namibia) during World War I, two of these locomotives were purchased second-hand by the SAR for use on the narrow gauge lines in that territory. The two locomotives remained in South West Africa after the war.
The Namaqua Copper Company's first 2 ft 6 in (762 mm) gauge locomotive, acquired in 1901, was a Dick, Kerr-built 0-4-2ST named Pioneer which was rebuilt from the 0-4-0ST format, possibly due to the additional weight of fuel tanks that were installed under the cab when it was converted to use fuel oil. The company also operated four more 0-4-2 tank locomotives, one 9 Ton and three 12 Ton, possibly also acquired from Dick, Kerr.:35–39
In 1904 a single 2 ft 6 in (762 mm) gauge 0-4-2 inverted saddle-tank locomotive named Caledonia was placed in service by the Cape Copper Company as a shunting engine at O'okiep in the Cape Colony.:25–27, 40
From the mid-1860s onwards the 0-4-2 wheel arrangement tended only to be used on tank engines in the United Kingdom. Exceptions were in Scotland on the Caledonian and Glasgow and South Western railways and in southern England on the London Brighton and South Coast Railway (LB&SCR) and the London and South Western Railway. The LB&SCR uniquely built express passenger 0-4-2 tender classes until 1891.
From 1868 the Great Western Railway built a number of standard gauge 0-4-2T classes for branch line passenger work to a design known as the 517 class by engineer George Armstrong. This design was developed until the GWR 1400 Class was built between 1932 and 1936, designed for push-pull autotrains. These were the last UK examples of this wheel arrangement. Four of them have been preserved.
William Stroudley of the LB&SCR built four very successful 0-4-2 classes, three tenders and one tank, between 1873 and 1891. The first of these was his powerful D-tank for suburban passenger work. One hundred and twenty five of these had been built by 1887, some of which survived in service until 1951. However, the most famous class were his Gladstone class express passenger locomotives, the first of which has been preserved.
- Science Museum, The British Railway Locomotive 1803-1853, H.M.S.O., 1958. p.13.
- Steam locomotive "Ajax" – Technical Museum Vienna
- :11–15, 18, 23
- Blackie, Article by D. Littley, SA Rail September–October 1989, Published by RSSA, p. 133.
- Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 20–25, 98–101, 110. ISBN 0869772112.
- Classification of S.A.R. Engines with Renumbering Lists, issued by the Chief Mechanical Engineer’s Office, Pretoria, January 1912, p. 2 (Reprinted in April 1987 by SATS Museum, R.3125-6/9/11-1000)
- Information supplied by John N. Middleton
- South African Railways and Harbours Narrow Gauge Locomotive Diagram Book, 2’0" Gauge, S.A.R. Mechanical Dept. Drawing Office, Pretoria, 28 November 1932
- Bagshawe, Peter (2012). Locomotives of the Namaqualand Railway and Copper Mines (1st ed.). Stenvalls. ISBN 978-91-7266-179-0.