In the

Whyte notation 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 twenti ...

for the classification of

steam locomotive 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 (usually coal, Fuel oil, oil or, rarely, Wood fuel, wood) to heat ...

wheel arrangement In rail transport, a wheel arrangement or wheel configuration is a system of classifying the way in which wheels are distributed under a locomotive. Several notations exist to describe the wheel assemblies of a locomotive by type, position, and c ...

, a 2-6-6-4 is a locomotive with a two-wheel leading truck, two sets of six

driving wheel On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons (or turbine, in the case of a steam turbine locomotive). On a conventional, non-articulated locomotive, the driving wheels are all coupled t ...

s, and a four-wheel

trailing truck On a steam locomotive, a trailing wheel or trailing axle is generally an unpowered wheel or axle (Wheelset (rail transport), wheelset) located behind the driving wheels. The axle of the trailing wheels is usually located in a trailing Bogie, t ...

. All 2-6-6-4s are simple

articulated locomotive An articulated locomotive is a steam locomotive (rarely, an electric 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 ...

s. Other equivalent classifications are: *

UIC classification The UIC classification of locomotive axle arrangements, sometimes known as the German classification''The Railway Data File''. Leicester: Silverdale, 2000. p. 52. . or German system,Kalla-Bishop P.M. & Greggio, Luciano, ''Steam Locomotives'', Cr ...

: (1'C)C2 (also known as German classification and

Italian classification The UIC classification of locomotive axle arrangements, sometimes known as the German classification''The Railway Data File''. Leicester: Silverdale, 2000. p. 52. . or German system,Kalla-Bishop P.M. & Greggio, Luciano, ''Steam Locomotives'', Cr ...

) *

French classification Under the French classification system for locomotive wheel arrangements, the system is slightly different for steam and electric/diesel vehicles. Steam The French system counts axles, rather than wheels. As with Whyte notation, a conventional r ...

: 130+032 *

Turkish classification In the Turkish classification system for railway locomotives, the number of powered axles are followed by the total number of axles. It is identical to the Swiss system except that the latter places a slash between the two numbers. Thus 0-6-0 bec ...

: 34+35 *

Swiss classification For more than a century, the Swiss locomotive, multiple unit, motor coach and railcar classification system, in either its original or updated forms, has been used to name and classify the rolling stock operated on the railways of Switzerland. ...

: 3/4+3/5 The

is refined to (1'C)C2 for simple articulated locomotives. The 2-6-6-4 was a fairly late development, a product of the

superpower steam "Superpower steam" was a term coined by Lima Locomotive Works in the mid-1920s, referring to steam locomotives with booster-equipped four-wheel trailing trucks supporting large fireboxes, as well as enlarged superheaters. The wheel arrangements in ...

concept, introduced by the

Lima Locomotive Works Lima Locomotive Works (LLW) was an American firm that manufactured railroad locomotives from the 1870s through the 1950s. The company's name is derived from the location of its main manufacturing plant in Lima, Ohio ( ). The shops were located be ...

, which encouraged the use of large fireboxes supported by four-wheel trailing trucks. Such a firebox could sustain a rate of steam generation to meet any demands of the locomotive's cylinders, even at high speed. High speeds were certainly among the design goals for the 2-6-6-4; most of the type were intended for use on fast freight trains. The first 2-6-6-4s built in the United States were for the

Pittsburgh and West Virginia Railroad The Pittsburgh and West Virginia Railway was a railroad in the Pittsburgh, Pennsylvania, and Wheeling, West Virginia, areas. Originally built as the Wabash Pittsburgh Terminal Railway, a Pittsburgh extension of George J. Gould's Wabash Railroad ...

, and these were not high-speed locomotives but rather mountain engines. They received three in 1934 and four more in 1937 and operated the 2-6-6-4s until 1953. The next of the type was a class of ten ordered by the

Seaboard Air Line The Seaboard Air Line Railroad , known colloquially as the Seaboard Railroad during its time, was an American railroad that existed from April 14, 1900, until July 1, 1967, when it merged with the Atlantic Coast Line Railroad, its longtime ri ...

in 1935 and 1937. These were high-speed freight engines and very successful. Upon

dieselization Dieselisation (US: dieselization) is the process of equipping vehicles with a diesel engine or diesel engines. It can involve replacing an internal combustion engine powered by petrol (US: gasoline) fuel with an engine powered by diesel fuel, ...

the class was sold to the

Baltimore and Ohio Railroad The Baltimore and Ohio Railroad was the oldest railroads in North America, oldest railroad in the United States and the first steam engine, steam-operated common carrier. Construction of the line began in 1828, and it operated as B&O from 1830 ...

in 1947, who operated them until 1953. The final class of 2-6-6-4s was the

Norfolk and Western Railway The Norfolk and Western Railway , commonly called the N&W, was a US class I railroad, formed by more than 200 railroad mergers between 1838 and 1982. It was headquartered in Roanoke, Virginia, for most of its existence. Its motto was "Precisio ...

's A class, built starting in 1936. 43 were built until 1950 but were operated until 1959 to prepare the ending of steam power. The powerful 2-6-6-4s were capable of more than 5,000 drawbar horsepower at and could reach , while pulling heavy coal trains. They were used until dieselization in 1959. In all, sixty 2-6-6-4s were constructed in North America. Only one remains:

Norfolk and Western 1218 Norfolk and Western 1218 is the only surviving example of the Norfolk and Western Railway’s (N&W) Norfolk and Western A class, A class 2-6-6-4 steam locomotive, steam locomotives. It was built in June 1943 by the Norfolk and Western's (N&W) Roa ...

was preserved and in 1987 was restored to running order, running on excursions until 1991. Today it is on display at the

Virginia Museum of Transportation The Virginia Museum of Transportation (VMT) is a museum in Downtown Roanoke, Virginia, that is devoted to the topic of transportation. History The Virginia Museum of Transportation began in 1963 as the Roanoke Transportation Museum in Wasena ...

References

Trains.com article on the 2-6-6-4 type
* Jeffries, Lewis I., ''N&W: Giant of Steam'' (Rev. ed. 2005). * Wrinn, Jim, ''Steam's Camelot: Southern and Norfolk Southern Excursions in Color'' (2000).

External links

picture of N&W 1218 pulling an excursion train in 1988side view of N&W 1218 under steam in 1987builder's photo of N&W 1212, engineer's side, Virginia Tech collectionbuilder's photo of N&W 1212, fireman's side, Virginia Tech collection
{{Whyte types 66,2-6-6-4