2-4-0+0-4-2

2-4-0+0-4-2 (Double Porter)

Equivalent classifications UIC class 1B+B1 French class 120+021 Turkish class 23+23 Swiss class 2/3+2/3, 4/6 from the 1920s Russian class 1-2-0+0-2-1

First known tank engine version First use 1915 Country Brazil Locomotive Q class Railway São Paulo Railway Designer Beyer, Peacock and Company Builder Beyer, Peacock and Company Evolved from 0-4-0+0-4-0

Equivalent classifications
UIC class	1B+B1
French class	120+021
Turkish class	23+23
Swiss class	2/3+2/3, 4/6 from the 1920s
Russian class	1-2-0+0-2-1

First known tank engine version
First use	1915
Country	Brazil
Locomotive	Q class
Railway	São Paulo Railway
Designer	Beyer, Peacock and Company
Builder	Beyer, Peacock and Company
Evolved from	0-4-0+0-4-0

Under the Whyte notation for the classification of steam locomotives by wheel arrangement, 2-4-0+0-4-2 is an articulated locomotive, usually of the Garratt type. The wheel arrangement is effectively two 2-4-0 locomotives operating back to back, with the boiler and cab suspended between the two power units. Each power unit has two leading wheels on one axle, four powered and coupled driving wheels on two axles and no trailing wheels. Since the 2-4-0 type is sometimes known as a Porter, the corresponding Garratt type would be referred to as a Double Porter. A similar wheel arrangement exists for Mallet locomotives, but is referred to as 2-4-4-2.

This was the second rarest Garratt wheel arrangement. Only five locomotives were constructed to this arrangement, four of which were built by Beyer, Peacock and Company (BP).

The four BP locomotives comprised three for the 5 ft 3 in (1,600 mm) São Paulo Railway of Brazil in 1915, and one for the 2 ft 6 in (762 mm) gauge Ceylon Government Railway (CGR) in 1929, the CGR’s class H1.

One more was built in 1919 by the São Paulo Railway, for its own use on 1,000 mm (3 ft 3 ³⁄₈ in) .

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