0-4-0+0-4-0

0-4-0+0-4-0

Tasmanian K class works photograph

Equivalent classifications UIC class B+B French class 020+020 Turkish class 22+22 Swiss class 2/2+2/2, 4/4 from the 1920s Russian class 0-2-0+0-2-0

First known tank engine version First use 1909 Country Australia Locomotive TGR K class Railway Tasmanian Government Railways Designer Beyer, Peacock and Company Builder Beyer, Peacock and Company Evolved to 2-4-0+0-4-2 Benefits Total engine mass as adhesive weight Drawbacks Instability at speed

Under the Whyte notation for the classification of steam locomotives by wheel arrangement, the 0-4-0+0-4-0 is an articulated locomotive of the Garratt type. The wheel arrangement is effectively two 0-4-0 locomotives operating back-to-back or face-to-face, with the boiler and cab suspended between the two power units. Each power unit has no leading wheels, four powered and coupled driving wheels on two axles and no trailing wheels. A similar arrangement exists for Mallet and Meyer locomotives, but is referred to as 0-4-4-0.

The first Garratt locomotive, K1, one of two 2 ft (610 mm) gauge Tasmanian Government Railways K class locomotives built in 1909, has this wheel arrangement and has been restored to operating condition at the Welsh Highland Railway. This arrangement proved one of the less popular Garratt types, since most Garratt locomotives were larger and more powerful, requiring more pairs of driving wheels to operate within the normal axle load limits, and because leading wheels gave more stability and better tracking to allow faster speeds.

In total, 34 Garratts of this type were constructed, seven by Garratt patent holder Beyer, Peacock, mostly for industrial use, and 27 by other builders. The largest user of the type was the C.F. Vicinaux du Mayumbe in the Belgian Congo, with twenty locomotives built to a 600 mm (1 ft 11 ⁵⁄₈ in) gauge by St. Leonard in Belgium.