Theboiler and cylinders were the same as the slightly earlierC class,[1] but itsdriving wheels had a larger diameter[2] and it was aesthetically different from the C. The class was ordered in a number of batches:[3] eight fromNeilson and Company in 1874, five fromDübs and Company and four from Neilson in 1878, seven from Neilson in 1880, ten fromScott Brothers in 1887, and the final D from Scott Brothers in 1890. The order withScott Brothers, placed in 1884, was the first large-scale construction of locomotives in New Zealand.[4]
The class was not particularly powerful and was employed on light duties, sometimes achieving speeds of 72.4 km/h (45 mph) on a level grade.[1] They often saw service on commuter trains betweenChristchurch andLyttelton until superior locomotives took their place,[5] and they were utilised at other major locations on theSouth Island's east coast.[6] In theNorth Island, D 137 was used in 1905 as part of a "railcar" trial service betweenLower Hutt andUpper Hutt,[7] hauling a carriage that seated 24 first class passengers, 48 second class passengers, and had a guard's compartment. It was inspired by locomotive/carriage combinations the General Manager of NZR witnessed in the easternUnited States. The combination was overpowered and uneconomic and did not last long in service.[8]
The first D to leave NZR's service went to thePublic Works Department in 1899, and three more followed in the next two years, one to the PWD and the other two to private businesses. The rest of the class continued to operate for over a decade. Withdrawal began duringWorld War I; the class had long since been superseded by newer and more powerful engines, but they were ideally sized for private sidings andbush tramways, so many were sold rather than scrapped.[1] Only eight remained in service at the start of 1920, and the last left NZR in May 1927.[9] The PWD and private industries continued to use them for decades - a few examples survived into the 1960s. This included D 137, which operated until 1963 on the truncated portion of theHutt Valley Line that remained as an industrialrail siding for the Gear Meat Preserving and Freezing Company.[10]
D 170 was on static display atHelensville station, until October 2024 when it was transferred back to MOTAT (who owns D 170) to be placed in storage to prevent further deterioration from the elements.
D 221 is on static display in Centennial Park inKaitaia
Another D (number unknown) is in a paddock in Kaingaroa.[12]
