NZR DA class

New Zealand DA class
DA 1400 on static display at MOTAT
Type and origin Power type Diesel-electric Builder General Motors Diesel (Canada) Electro-Motive Division (USA) Clyde Engineering (Australia) Model EMD G12 Build date 1955 - 1967
Specifications Configuration: ​  • UIC A1A-A1A Gauge 3 ft 6 in (1,067 mm) Length GMD/EMD 14.1 metres (46 ft 3 in) Clyde 14.6 metres (47 ft 11 in) Adhesive weight 59.0 tonnes (58.1 long tons; 65.0 short tons) Loco weight GMD/EMD 81.0 tonnes (79.7 long tons; 89.3 short tons) Clyde 79.0 tonnes (77.8 long tons; 87.1 short tons) Fuel type Diesel Prime mover EMD 12-567C and EMD 12-567E RPM range 835 rpm Engine type V12 Diesel engine Aspiration Roots type supercharger Displacement 111.49 L (6,804 cu in) Traction motors Four EMD D19 or D29 Cylinders 12 Cylinder size 216 mm × 254 mm (8.5 in × 10.0 in)
Performance figures Maximum speed 100 km/h (62 mph) Power output 1,060 kW (1,420 hp) Tractive effort 140 kN (31,000 lbf)
Career Number in class 146 Numbers DA 1400–1545 (original) DA 11–996 (TMS) First run 1955 - 1967 Last run 1977 - 1989 Current owner Motat, Steam Incorporated, Dean McQuoid, Feilding and District Steam Rail Society Disposition 85 rebuilt as DC Class 6 as DAA (defunct), 1 as DAR 517 (withdrawn); 0 in service

The New Zealand D^A class diesel-electric mainline locomotives operated on the New Zealand railway system between 1955 and 1989. With 146 locomotives, it was the most numerous class to ever operate in New Zealand, with five more than the A^B class steam locomotive.

The class were A1A-A1A versions of the Electro-Motive Diesel G12 model, with the design altered slightly to run on New Zealand's 3 ft 6 in (1,067 mm) rail system, and fit the small loading gauge. They were introduced between 1955 and 1967, and were the first class of diesel locomotives to seriously displace steam traction.

Between 1978 and 1983, 85 were rebuilt as the DC class, of which many are still in use. All but one of the remainder were withdrawn by 1989, with six preserved. The last locomotive was refitted for shunting duties, becoming DAR 517.

The D^A class have their origins in the post-World War II period. Like most nations New Zealand’s dominant form of traction was steam, with electrification being used in Wellington, the Christchurch - Lyttleton Line and through the Otira Tunnel. The General Manager of the Railways Department, Frank Aickin, was an advocate for electrifying the entire North Island Main Trunk (NIMT) to alleviate the shortage of coal and the cost of importing diesel fuel; though he also recognised that steam and diesel traction would be required on other lines.

Aickin went as far as negotiating a tentative contract for construction, but fell out with the Government in 1951 and retired. His successor, H.C. Lusty, terminated the contract. After a disappointing experience with the D^F class and facing significant capacity issues on the North Island Main Trunk (NIMT) NZR entered into an agreement with General Motors for the supply of 30 G12 model locomotives following a tender process. Designated by the Railways Department as the D^A class one of the major appeals was the guarantee of delivery within five months. With two production lines at London, Ontario and La Grange, Illinois two locomotives were completed every three days.