4-6-6-2
Encyclopedia
In Whyte notation
, a 4-6-6-2 is a steam locomotive
with four leading wheel
s (two axles) in an unpowered bogie
at the front of the locomotive followed by two sets of driving wheel
s with six wheels each (three axles each), followed by two unpowered trailing wheel
s (one axle) at the rear of the locomotive.
Other equivalent classifications are:
UIC classification
: 2CC1 (also known as German classification and Italian classification)
French classification: 230+031
Turkish classification
: 35+34
Swiss classification: 3/5+3/4
This locomotive wheel arrangement was used in only a very limited number of locomotives in North America
, most notably as class MM-2
cab forward
locomotives on the Southern Pacific Railroad
. These were effectively 2-6-6-4
s running in reverse. They were originally built as 2-6-6-2
s but were refitted with a four-wheel leading truck to increase stability at speed.
Whyte notation
The Whyte notation for classifying steam locomotives by wheel arrangement was devised by Frederick Methvan Whyte and came into use in the early twentieth century encouraged by an editorial in American Engineer and Railroad Journal...
, a 4-6-6-2 is a steam locomotive
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
with four leading wheel
Leading wheel
The leading wheel or leading axle 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 in a truck...
s (two axles) in an unpowered bogie
Bogie
A bogie is a wheeled wagon or trolley. In mechanics terms, a bogie is a chassis or framework carrying wheels, attached to a vehicle. It can be fixed in place, as on a cargo truck, mounted on a swivel, as on a railway carriage/car or locomotive, or sprung as in the suspension of a caterpillar...
at the front of the locomotive followed by two sets of driving wheel
Driving wheel
On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons...
s with six wheels each (three axles each), followed by two unpowered trailing wheel
Trailing wheel
On a steam locomotive, a trailing wheel or trailing axle is generally an unpowered wheel or axle located behind the driving wheels. The axle of the trailing wheels was usually located on a trailing truck...
s (one axle) at the rear of the locomotive.
Other equivalent classifications are:
UIC classification
UIC classification
The UIC classification of locomotive axle arrangements describes the wheel arrangement of locomotives, multiple units and trams. It is set out in the International Union of Railways "Leaflet 650 - Standard designation of axle arrangement on locomotives and multiple-unit sets". It is used in much...
: 2CC1 (also known as German classification and Italian classification)
French classification: 230+031
Turkish classification
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.Thus0-6-0 becomes 33...
: 35+34
Swiss classification: 3/5+3/4
This locomotive wheel arrangement was used in only a very limited number of locomotives in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, most notably as class MM-2
Southern Pacific class MM-2
Southern Pacific Company's MM-2 class of steam locomotives was Southern Pacific's only class of 2-6-6-2 locomotives ordered and built as cab forward locomotives. They were built in 1911 by Baldwin Locomotive Works and entered service on SP beginning September 19, 1911. By 1914, they had all been...
cab forward
Cab forward
The term cab forward refers to various rail and road vehicle designs which place the driver's compartment substantially farther towards the front than is common practice.- Rail locomotives :...
locomotives on the Southern Pacific Railroad
Southern Pacific Railroad
The Southern Pacific Transportation Company , earlier Southern Pacific Railroad and Southern Pacific Company, and usually simply called the Southern Pacific or Espee, was an American railroad....
. These were effectively 2-6-6-4
2-6-6-4
In the Whyte notation for the classification of steam locomotive wheel arrangement, a 2-6-6-4 is a locomotive with a two-wheel leading truck, two sets of six driving wheels, and a four-wheel trailing truck...
s running in reverse. They were originally built as 2-6-6-2
2-6-6-2
In Whyte notation, 2-6-6-2 refers to a railroad steam locomotive that has two leading wheels followed by six coupled driving wheels, a second set of six coupled driving wheels, and two trailing wheels...
s but were refitted with a four-wheel leading truck to increase stability at speed.