The NZR DS class locomotive is a type of 16 diesel shunting locomotives built by the Vulcan Foundry and supplied by the Drewry Car Co from 1949âÂÂ1955, for New Zealand Railways (NZR).
In the late 1940s, NZR was looking for a more powerful type of diesel shunting locomotive to work in the Wellington railway yards. They had trialled a number of T<sup>R</sup> class shunting locomotives, none at the time were suitable with the most powerful being the five T<sup>R</sup> class 0-4-0DM shunting locomotives which produced 153 horsepower. These locomotives were too small for the large Wellington yards, where a more powerful locomotive would be needed. Two more were built for the private Whakatane Board Mills Ltd Matahina Tramway in the Bay of Plenty. Both of these locomtovies are preserved.
In 1948, the Tasmanian Government Railways took delivery of four Drewry 0-6-0DM shunting locomotives based on the Class 04 shunting locomotives being built for British Railways. These locomotives, Tasmanian Government Railways V class, were powered by a Gardner 8L3 diesel engine producing 204 hp, and weighed 25.6 tonnes. These locomotives were of a standard Drewry design but built by English Electric at their Vulcan Works. A similar diesel locomotive had been built for the Ohai Railway Board in Southland, makers N<sup>O</sup> 2248/D68 of 1947.
The first batch of four Drewry 0-6-0DM D<sup>S</sup> class locomotives arrived in Wellington in 1949 for evaluation. They were allocated the numbers D<sup>S</sup> 205 - 208, with D<sup>S</sup> 205 and D<sup>S</sup> 206 entering service in August of that year, while D<sup>S</sup> 207 and D<sup>S</sup> 208 entered service in September 1949. All four locomotives were put to work in the Wellington railway yards immediately after entering into service.
Despite some teething troubles, the initial four locomotives were sufficiently capable of performing the work required. The Railways Department was pleased with the results, and in 1953 ordered seven more locomotives, of Drewry type A-1. At 26ý tons, the new arrivals were slightly heavier than the original four units, which weighed 25.5 tons. The locomotives were fitted with Westinghouse air-brakes, which were more powerful than the original locomotive brakes.
The new locomotives were given numbers D<sup>S</sup> 209 - 215 and were purchased for work in the South Island. However, two stayed in the North Island temporarily, while the other five were sent to Lyttelton. Here, the new D<sup>S</sup> class diesel locomotives replaced the F class 0-6-0ST steam tank locomotives used to shunt the wharves (although the F class did, in fact, remain on hand to shunt the Boat Train onto the Ferry Wharf at Lyttelton for some years after that).
In 1954, NZR purchased another five A-1 type locomotives, numbers D<sup>S</sup> 200 - 204, for wharf shunting in the South Island. These locomotives were the last of the D<sup>S</sup> class to enter service in 1955, with the last being D<sup>S</sup> 204 in June 1955. The next class of shunting locomotives was classed D<sup>SA</sup> based on the Drewery "A-2" type. Another three similar locomotives were built for industrial users to a similar pattern.
All of the D<sup>S</sup> class locomotives and variants were powered by a Gardner 8L3 diesel engine producing 204 hp at 1200 rpm, coupled to a Wilson five-speed epicyclic gearbox with fluid transmission in turn connected to a final reduction and reverse unit. Power was transmitted to the wheels via a jackshaft, to which the wheels were connected by coupling rods. This jackshaft was located under the cab.
The locomotives had a tractive effort of 14,300 lb in low gear, which enabled it to move loads of up to 1000 tons in low gear at walking speed. In a higher gear, the locomotives could haul a lighter load at speeds of up to 30 mph, a respectable figure for a locomotive that had relatively small (39þ") driving wheels.
The withdrawal of the class began in the early 1980s. Several entered into industrial service, while three - D<sup>S</sup> 202, D<sup>S</sup> 203, and D<sup>S</sup> 207 were purchased for preservation by Steam Incorporated, Ocean Beach Railway, and the Glenbrook Vintage Railway. Since then, another four have entered preservation since, D<sup>S</sup> 213 (TMS DS134) and D<sup>S</sup> 215 (DS157), with the Midland Rail Heritage Trust, D<sup>S</sup> 201 (TMS DS36) at the Ohai Railway Board Heritage Trust's site in Wairio, while D<sup>S</sup> 214 (TMS DS140) has now been turned into a display at Steampunk HQ, Oamaru.