4-8-8-2
Encyclopedia
Under the Whyte notation
for the classification of steam locomotive
s, a 4-8-8-2 is a locomotive with four leading wheel
s, two sets of eight driving wheel
s, and a two-wheel trailing truck.
Other equivalent classifications are:
UIC classification
: 2DD1 (also known as German classification and Italian classification)
French classification: 240+041
Turkish classification
: 46+45
Swiss classification: 4/6+4/5
The equivalent UIC classification
is refined to (2'D)D1' for Mallet locomotives.
Because of its length, such a locomotive must be an articulated locomotive
. All of the examples produced had a hinged joint between the first and second groups of driving wheels. Furthermore, all examples of this type were cab forward
s. Normally, the leading truck sits under the smokebox and the trailing truck under the firebox. On a cab-forward, the leading truck also supports the firebox, and the trailing truck and smokebox are at the rear next to the tender. A 4-8-8-2 is effectively a 2-8-8-4
that always runs in reverse. Although commonly called Mallets they were not of this type, because unlike Mallets, which use compound expansion, these cab-forwards were built with simple expansion cylinders. The name stuck because the original classes of Southern Pacific cab-forwards were built as Mallets, though these were also eventually converted to simple expansion.
The Southern Pacific
was the only railroad to operate engines of this wheel arrangement. All were built by the Baldwin Locomotive Works
.
One example, Southern Pacific 4294
, is the only cab forward that survives today. It is kept at the California State Railroad Museum
.
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...
for the classification of 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...
s, a 4-8-8-2 is a locomotive 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 sets of eight driving wheel
Driving wheel
On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons...
s, and a two-wheel trailing truck.
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...
: 2DD1 (also known as German classification and Italian classification)
French classification: 240+041
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...
: 46+45
Swiss classification: 4/6+4/5
The equivalent 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...
is refined to (2'D)D1' for Mallet locomotives.
Because of its length, such a locomotive must be an articulated locomotive
Articulated locomotive
Articulated locomotive usually means a steam locomotive with one or more engine units which can move independent of the main frame. This is done to allow a longer locomotive to negotiate tighter curves...
. All of the examples produced had a hinged joint between the first and second groups of driving wheels. Furthermore, all examples of this type were 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 :...
s. Normally, the leading truck sits under the smokebox and the trailing truck under the firebox. On a cab-forward, the leading truck also supports the firebox, and the trailing truck and smokebox are at the rear next to the tender. A 4-8-8-2 is effectively a 2-8-8-4
2-8-8-4
Under the Whyte notation for the classification of steam locomotives, a 2-8-8-4 is a steam locomotive with two leading wheels, two sets of eight driving wheels, and a four-wheel trailing truck.Other equivalent classifications are:...
that always runs in reverse. Although commonly called Mallets they were not of this type, because unlike Mallets, which use compound expansion, these cab-forwards were built with simple expansion cylinders. The name stuck because the original classes of Southern Pacific cab-forwards were built as Mallets, though these were also eventually converted to simple expansion.
The Southern Pacific
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....
was the only railroad to operate engines of this wheel arrangement. All were built by the Baldwin Locomotive Works
Baldwin Locomotive Works
The Baldwin Locomotive Works was an American builder of railroad locomotives. It was located in Philadelphia, Pennsylvania, originally, and later in nearby Eddystone, Pennsylvania. Although the company was very successful as a producer of steam locomotives, its transition to the production of...
.
One example, Southern Pacific 4294
Southern Pacific 4294
Southern Pacific 4294 was the last steam locomotive ordered new by Southern Pacific Railroad . It was built by Baldwin Locomotive Works in March 1944, and was used hauling SP's trains over the Sierra Nevada Mountains, often working on Donner Pass in California.- Construction and use :4294 was the...
, is the only cab forward that survives today. It is kept at the California State Railroad Museum
California State Railroad Museum
The California State Railroad Museum is a museum in the state park system of California, USA, interpreting the role of the "iron horse" in connecting California to the rest of the nation. It is located in Old Sacramento at 111 I Street....
.