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. This arrangement is commonly called Adriatic.
Other equivalent classifications are:
- UIC classification: 1C2 (also known as German and Italian classifications)
- French classification: 132
- Turkish classification: 36
- Swiss classification: 3/6
With three known exceptions, the wheel arrangement was usually used on tank locomotives.
The earliest known example was the South African Class 6Z, designed by Cape Government Railways (CGR) Chief Locomotive Superintendent H.M. Beatty in 1901. The first of the class were modified 2-6-2 Prairie locomotives that were equipped with two axle trailing bogies. In 1902 more were placed in service, built with the 2-6-4 wheel arrangement. The latter were the first tender locomotives in the world to be built with this wheel arrangement.
Two Austrian express locomotive types were also of the same wheel arrangement, the Class 210 of 1908 and Class 310 of 1911, both designed by Karl Gölsdorf. The type therefore became known as the Adriatic arrangement, named for the Adriatic Sea which bordered Austria-Hungary until 1918.
Tank engines with the 2-6-4 wheel arrangement were produced for many different railway systems worldwide and were mainly used for freight and suburban passenger working. They have been less successful on express passenger trains.
Finland had three locomotive classes with a 2-6-4T wheel arrangement, the Classes Vk1, Vk2 and Vk3. All three classes were nicknamed “Iita”, while the Class Vk1s were also nicknamed “Amerikan” because they were built by Baldwin Locomotive Works.
The Class Vk1s, numbered 301 to 305, were delivered in 1900 from Baldwin Locomotive Works of Philadelphia, Pennsylvania.
The Class Vk2s were numbered 454 to 455.
The Finnish Steam Locomotive Class Vk3s were numbered 456 and 487 to 492. They were built in 1915 by Tampella, a Finnish heavy industry manufacturer, and were used for local passenger duties. One of them, Vk3 No 489, is preserved at the Finnish Railway Museum.
Two Deutsche Bundesbahn (DB) 2-6-4T Class 66 locomotives, designed for fast goods train and passenger train service, were built in 1955 as part of the DB's Neubaulok construction programme. They were both withdrawn from service in 1968. One, DB 66 002, has been preserved at the Bochum-Dahlhausen Railway Museum.
The Ferrymead Railway in Christchurch, New Zealand has a 3 ft 6 in (1,067 mm) Cape gauge 2-6-4T tank locomotive that was in regular operation until taken off-line for boiler repairs around 2009. It was built by Baldwin in 1901.
The Wf class of the New Zealand Government Railways was built between 1903 and 1928 and was a general purpose tank design. It was used all over New Zealand and identical locomotives were also in service as the Ds class of the Tasmanian Government Railways. Three Wf class locomotives survived in preservation:
- Wf386, one of the engines used on the first Wellington to Auckland train, is preserved at Paekakariki.
- Wf393 is preserved at Ferrymead.
- Wf403 is preserved at Nelson.
Between 1898 and 1900 the Pretoria-Pietersburg Railway (PPR) placed six 2-6-4T tank locomotives in service, built by Beyer, Peacock and Company. During the Anglo-Boer War they were first taken over by the Nederlandsche-Zuid-Afrikaansche Spoorwegmaatschappij (NZASM) and then by the Imperial Military Railways (IMR). After the war they were taken onto the roster of the Central South African Railways (CSAR) and in 1912 they were assimilated into the South African Railways (SAR) as Class D.
In 1901 the Cape Government Railways (CGR) placed four Cape Class 6 2-6-2 Prairie tender steam locomotives in service, designed at the Salt River works of the CGR and built by Neilson, Reid and Company. During trials it was found that they were inclined to be unsteady at speed and the locomotive design was therefore modified to a 2-6-4 Adriatic wheel arrangement by replacing the trailing carrier wheels with a two axle bogie. Another four locomotives incorporating this modification were ordered later in 1901 and delivered in 1902, the first tender locomotives in the world to be built with this wheel arrangement. The change in design resulted in a marked improvement in the locomotive’s stability at speed and the first four locomotives were therefore also modified accordingly. In 1912, when they were assimilated into the SAR, these eight locomotives were all reclassified to Class 6Z.
In 1902 the CGR placed two Type A Adriatic narrow gauge locomotive in construction service on the Avontuur branch, which was being built out of Port Elizabeth through the Langkloof. They were built by Manning Wardle and Company and at a width of 7 feet 9 inches (2.362 metres), they were the widest locomotives to see service on any of the 2 feet (610 millimetres) narrow gauge lines in South Africa.:112, 156
The first British examples of the 2-6-4T wheel arrangement were two locomotives built for the narrow-gauge Leek & Manifold Valley Light Railway in 1904. The first 4 ft 8 1⁄2 in (1,435 mm) standard gauge examples were the class 1B of the Great Central Railway, built in 1914.
Richard Maunsell of the South Eastern and Chatham Railway (SECR) designed the K class in 1914 for express passenger duties, and in 1925 introduced a three cylinder variant K1 class for the Southern Railway. These locomotives proved to be unsteady at speed and, following the Sevenoaks railway accident in 1927, they were rebuilt as 2-6-0 tender locomotives. Maunsell did however use the type more successfully for his W class freight locomotives of 1930.
Between 1927 and 1947 the London, Midland and Scottish Railway (LMS) built nearly five hundred 2-6-4Ts for suburban passenger work to four similar designs (see LMS/BR Class 4 2-6-4T locomotives). The last of these, the LMS Fairburn, continued to be built by British Railways (BR) until 1951. Fairburn's LMS design also formed the basis of the very successful BR Standard Class 4, which continued to be produced until 1957.
Between 1946 and 1950 George Ivatt of the LMS also built eighteen 5 ft 3 in (1,600 mm) Irish gauge examples of a very similar design at Derby Works, for use in Northern Ireland. These later became the Northern Counties Committee WT class.
A prototype of the London and North Eastern Railway (LNER) L1 class, designed by Edward Thompson, was built in 1945. The remaining ninety-nine members of the class were built under BR administration during the period from 1948 to 1950.
- Durrant, A E (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. p. 11. ISBN 0715386387.
- Neilson, Reid works list, compiled by Austrian locomotive historian Bernhard Schmeiser
- Holland, D.F. (1971). Steam Locomotives of the South African Railways, Volume 1: 1859-1910 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 52–54, 56, 120, 122, 126. ISBN 978-0-7153-5382-0.
- Garner, John (1996). Guide to New Zealand Rail Heritage. IPL Books. ISBN 0-908876-99-8.
- Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. p. 136. ISBN 978-0-7153-5427-8.
- Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 29, 45. ISBN 0869772112.
- Classification of S.A.R. Engines with Renumbering Lists, issued by the Chief Mechanical Engineer’s Office, Pretoria, January 1912, pp. 7, 11, 13, 19 (Reprinted in April 1987 by SATS Museum, R.3125-6/9/11-1000)
- Haresnape, Brian; Rowledge, Peter (May 1982). Robinson Locomotives: A Pictorial History. Shepperton: Ian Allan. p. 106. ISBN 0-7110-1151-6. DX/0582.
- Tandem Associates - Lionel Locomotives