Under the

Whyte notation 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 ce ...

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, oil or, rarely, wood) to heat water in the locomot ...

s, represents the

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 ...

of no

leading wheel 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 ...

s, six powered and coupled

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 ...

s on three axles and six

trailing wheel On a steam locomotive, a trailing wheel or trailing axle is generally an unpowered wheel or axle ( wheelset) located behind the driving wheels. The axle of the trailing wheels is usually located in a trailing truck. On some large locomotives, ...

s on three axles.

Overview

The wheel arrangement was usually found on Single Fairlie or Mason Bogie locomotives. The

Fairlie locomotive A Fairlie is a type of articulated locomotive, articulated steam locomotive that has the driving wheels on bogies. The locomotive may be double-ended (a double Fairlie) or single ended (a single Fairlie). Fairlies are most famously associated ...

was invented and patented in 1864 by the Scottish engineer

Robert Francis Fairlie Robert Francis Fairlie (either March 1831 or 5 April 1830, in Glasgow – 31 July 1885, in London) was a Scottish-born railway engineer. Early life Fairlie was born in Glasgow, the son of T. Archibald Fairlie (an engineer) and Margaret Fairlie ...

. The first Fairlie locomotives later became known as Double Fairlies. A variation of the original Fairlie concept was the Single Fairlie, also known as the Mason Fairlie. The Single Fairlie design was essentially half a Double Fairlie. It retained the ability to negotiate sharp curves and, while it abandoned the bidirectional nature of the Double Fairlie, it regained the ability of conventional locomotives to have a large water and coal bunker behind the cab and to use a trailing tender if necessary. Most Single Fairlies were tank locomotives and early models were similar in general appearance to conventional tank engines with side tanks and a coal bunker aft of the cab, all mounted on a single rigid frame. The pivoting engine unit was mounted under the boiler and the unpowered bogie under the cab and bunker. Later models were similar in appearance to conventional tender locomotives. It was developed by

William Mason William, Willie, or Willy Mason may refer to: Arts and entertainment *William Mason (poet) (1724–1797), English poet, editor and gardener *William Mason (architect) (1810–1897), New Zealand architect *William Mason (composer) (1829–1908), Ame ...

in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

, where the type became known as the

Mason Bogie Mason Bogie locomotives (also known as Mason Fairlie locomotives) are a type of articulated steam locomotive suited for sharp curves and uneven track, once commonly used on narrow gauge railways in the United States of America. The design is a de ...

. It had one boiler at the front, a cab in the centre and a water-and-coal bunker at the rear end, all mounted on a single rigid frame, with a single engine unit under the boiler and an unpowered bogie under the bunker.Havron, Michael. ''Records of the MASON LOCOMOTIVE WORKS, Taunton, Massachusetts''. Railway & Locomotive Historical Society, Computerized by J.F. Webber. pp. 28-36.
(Accessed on 4 November 2016)

Usage

United States

The first known 0-6-6T locomotive was built for the gauge

New Bedford Railroad The New Bedford Railroad was a railroad in Massachusetts. It was incorporated on July 1, 1873, as a merger between the New Bedford and Taunton Railroad, the Taunton Branch Railroad, and the Middleborough and Taunton Railroad. The main line ran fr ...

Mason Machine Works The Mason Machine Works was a machinery manufacturing company located in Taunton, Massachusetts, between 1845 and 1944. The company became famous for an early invention by its creator, William Mason, the self-acting mule, first patented in 1840 ...

in May 1874. It was apparently not numbered, but bore the name ''Wm. Mason''. The locomotive later went to the Boston, Clinton & Fitchburg as its no. 23, then to the Old Colony as its no. 108 and finally to the New York, New Haven & Hartford as its no. 708. More 0-6-6T locomotives were produced by Mason between 1875 and 1881. Many of them were subsequently rebuilt to a wheel arrangement.

References

{{Whyte types 6,0-6-6T 6,0-6-6T