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4-4-2+2-4-4

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4-4-2+2-4-4 (Double Atlantic)
Diagram of two small leading wheels, two large driving wheels joined by a coupling rod, two small trailing wheels, two large driving wheels joined by a coupling rod, and two small leading wheels
Equivalent classifications
UIC class2B1+1B2
French class221+122
Turkish class25+25
Swiss class2/5+2/5, 4/10 from the 1920s
Russian class2-2-1+1-2-2
First known tank engine version
First use1912
CountryAustralia
LocomotiveTGR M class
RailwayTasmanian Government Railways
DesignerBeyer, Peacock & Company
BuilderBeyer, Peacock & Company

Under the Whyte notation for the classification of steam locomotives by wheel arrangement, a 4-4-2+2-4-4 is a Garratt articulated locomotive. The wheel arrangement is effectively two 4-4-2 locomotives operating back to back, with each power unit having four leading wheels on two axles in a leading bogie, four powered and coupled driving wheels on two axles, and two trailing wheels on one axle in a trailing truck. Since the 4-4-2 type is usually known as an Atlantic, the corresponding Garratt type is often referred to as a Double Atlantic.

Overview

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The 4-4-2+2-4-4 was not a common Garratt wheel arrangement. Only ten were built, all by Beyer, Peacock & Company, the owner of the Garratt patent.[1]

Usage

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Argentina

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Eight locomotives were built for Argentina to run on 4 ft 8+12 in (1,435 mm) standard gauge.[1]

After nationalization in 1948, all these locomotives were rostered on the General Urquiza Railway.[1]

Australia

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The first Garratt locomotives to be built to the 4-4-2+2-4-4 wheel arrangement were a pair of M class passenger locomotives for the 3 ft 6 in (1,067 mm) gauge Tasmanian Government Railways in Australia in 1912. They were acquired to haul express passenger trains between Launceston and Hobart.[1][2]

The two M class engines were the only eight-cylinder Garratt locomotives in the world. They were difficult to maintain and, despite their haulage abilities and speed, both were withdrawn from service some time after the arrival of the R class in 1924 and scrapped in the late 1940s.[2]

References

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  1. ^ a b c d e f g Hamilton, Gavin N., The Garratt Locomotive - Garratt Locomotives produced by Beyer, Peacock, retrieved 10 November 2012
  2. ^ a b A Brief History of the Garratt Locomotive in Australia Australian Railway Historical Society Bulletin issue 185 March 1953 page 25
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Media related to 4-4-2+2-4-4 locomotives at Wikimedia Commons