Under the Whyte notation for the classification of steam locomotives, 2-6-0+0-6-2 represents the wheel arrangement of an articulated locomotive with two separate swivelling engine units, arranged back to back with the boiler and cab suspended between them. Each engine unit has two leading wheels in a leading truck, six powered and coupled driving wheels on three axles and no trailing wheels.
The arrangement is effectively two 2-6-0 locomotives operating back-to-back and was used on Garratt articulated locomotives. Since the 2-6-0 type was often known as a Mogul, the corresponding Garratt type was usually known as a Double Mogul.
A similar wheel arrangement exists for Mallet steam locomotives on which only the front engine unit swivels, but these are referred to as 2-6-6-2.
The 2-6-0+0-6-2 was the second Garratt type to appear after the original 0-4-0+0-4-0 and was first used on the fourth through ninth Garratts to be constructed.
A group of six locomotives of 3 ft 6 in (1,067 mm) gauge were constructed for the Western Australian Government Railways in 1911 as their Class M. Further locomotives for this railway included seven more Class Ms locomotives in 1912.
The Australian Portland Cement Company took delivery of two 3 ft 6 in (1,067 mm) gauge locomotives in 1936 and 1939, as their no. 1 and no. 2 engines for the quarry line at Fyansford, Victoria. These engines replaced two Vulcan Iron Works 0-6-0 saddle-tanks on the mainline haul until they were later displaced by Australian Standard Garratt no. G33.
Fyansford’s no. 2, by then a combination of no. 2's centre unit and no. 1's engine units, was in service until 1966, when the quarry line was replaced by a conveyor belt. Fyansford no. 2 was to be evaluated in 2015 for return to service on the Bellarine Railway, after having been moved there from the Menzies Creek Museum of the Puffing Billy Railway in 2010.
Between 1919 and 1925, the South African Railways (SAR) placed five Class NG G11 Garratt locomotives with this wheel arrangement in service on the Avontuur 2 ft (610 mm) narrow gauge line through the Langkloof and also in Natal. They were the first Garratt locomotives to enter service in South Africa. The three locomotives, numbered 51 to 53, were erected at Uitenhage and put on trials on the Avontuur line in May 1920. These first three locomotives were not superheated. They had outside plate frames, Walschaerts valve gear, Belpaire fireboxes and used saturated steam and slide valves.
Having been proven successful during trials, another two locomotives were ordered from BP. Numbers 54 and 55 were delivered in 1925 and placed in service in Natal. Since these two were superheated, they had longer smokeboxes and were 9 1⁄2 inches (241 millimetres) longer in overall length, while the incorporation of piston valves required alteration of the valve gear. The cabs of the second order locomotives were also improved to offer better protection to the crew.
In February 1921, the SAR placed a single experimental Class GA Garratt 2-6-0+0-6-2 locomotive in service. It was ordered from BP in 1914, together with the order for the narrow gauge Class NG G11 Garratts, but wartime hostilities also delayed its delivery until 1920. It was the first Cape gauge Garratt to enter service in South Africa.
The locomotive was superheated, with a Belpaire firebox, a plate frame and Walschaerts valve gear. It was erected in the Durban shops and placed in trial service on the Natal mainline. During the trials it was found that the absence of trailing carrying wheels on the engine units was a disadvantage, since it led to excessive flange wear on the driving wheels. As a result, the locomotive remained the only representative of its Class and all subsequent Garratt models of the SAR were equipped with trailing Bissel trucks on their engine units. The locomotive was withdrawn from service in 1938 because of a cracked frame and scrapped.
One 21st century example of this wheel arrangement has been built for the Wells and Walsingham Light Railway, a 10 1⁄4 in (260 mm) gauge heritage railway in Norfolk, England.
An earlier 2-6-0+0-6-2 Garratt, no. 3, the Norfolk Hero, was built by Neil Simkins in 1986. In 2010, the fleet was augmented by a new Garratt, no. 6, the Norfolk Heroine.