The NZR G class was a type of Garratt steam locomotive used in New Zealand, later rebuilt as Pacific type locomotives. They were the only Garratt type steam locomotives ever used by the New Zealand Railways (NZR). They were ordered to deal with traffic growth over the heavy gradients of the North Island Main Trunk (NIMT) and to do away with the use of banking engines on steep grades. They were one of the few Garratt designs to employ six cylinders. A mechanical stoker was used to feed coal into the locomotive. Introduction About 1913, General Manager E H Hiley considered the importing of ten articulated Garratt engines and ten Pacifics. With the success of the AB class and WAB class Pacifics no more was heard of Garratts. Then with the retirement in 1925 of the Chief Mechanical Engineer E E Gillon his successor G S Lynde invited Beyer, Peacock & Company of England to suggest a suitable Garrett for the NIMT, and they were then asked to quote for engines with either four or six cylinders. But the three six-cylinder engines were supplied "against their own better judgement. The influence of the London & North Eastern Railway three-cylinder enthusiasts (i.e. Lynde) was evident in this unwise decision." These engines had three cylinders () on each of the two set of engine frames, thus creating a 6-cylinder Garratt. The engines entered service in 1929. Walschaerts valve gear operated the outside cylinders with the inner third cylinder operated by a Gresley-Holcroft mechanism. The locomotives proved a disaster on the light NZR tracks. It has been suggested the most likely reason was that the engines were too powerful for the system and also the valve gear mechanisms were complicated. The design was most unusual in that the coal bunker was carried on an extension to the boiler frame rather than the normal Garratt positioning on the rear engine's frame. Unlike a Union Garratt the rear water tank was still mounted on the rear engine unit. The engines operated at and delivered of tractive effort which, on the lightly laid New Zealand tracks, proved to be too powerful for the drawbars on rolling stock and broken drawbars occurred wherever the engines ran. Further, the locomotives when hauling a full load, generated such intense heat in restricted tunnels, which are common in New Zealand, that crews disliked working them. Their large size driving wheels