New Zealand DG and DH class locomotive

New Zealand DG and DH class

Dg 772 on the Ferrymead Railway.

Type and origin Power type Diesel-Electric Builder English Electric and Vulcan Foundry / Robert Stephenson & Hawthorn, United Kingdom Build date 1955 - 1956

Specifications Configuration: ​  • UIC A1A - A1A Length 14.7 metres (48 ft 3 in) Adhesive weight 46.6 tonnes (45.9 long tons; 51.4 short tons) DG 48.4 tonnes (47.6 long tons; 53.4 short tons) DH Loco weight 70 tonnes (69 long tons; 77 short tons) Prime mover English Electric 6SRKT Mk 2 RPM range 850 rpm Traction motors Four EE 525 / 2A Cylinders I6 Cylinder size 254 mm × 305 mm (10.0 in × 12.0 in)

Performance figures Maximum speed 97 km/h (60 mph) Power output 560 kW (750 hp) Tractive effort 114 kN (26,000 lbf) DG 130 kN (29,000 lbf) DH

Career Number in class 31 DG 11 DH Numbers 750 - 791 (original) 2007 - 2497 (TMS) Locale All of New Zealand First run 6 September 1955 Last run 16 May 1983 Disposition 38 scrapped 4 preserved

The New Zealand DG and DH class locomotive were a type of diesel-electric locomotives in operation on New Zealand's rail network from 1955-1983, built by English Electric.

Due a change in government dieselisation strategy 21 of the original order for D^F class were changed to 42 D^G class locomotives, being a half-sized version of the D^F with only one cab instead of two, and a similar Bulldog nose. The English Electric Co, as they did with many of their diesel locomotives of the 1950s-60s, did not assemble them at the Preston works, but allocated the final assembly of build numbers 2254/E7821-2273/E7840 (road no. 750-769) to Robert Stephenson & Hawthorn and build numbers 2274/D353-2295/D374 (road no. 770-791) to Vulcan Foundry, both English Electric plants. The South Island allocated locomotives were initially classified D^H because they were fitted with adjustable bogies that allowed a higher maximum axle weight and tractive effort.

The first regular outing by a D^G class locomotive was that of D^G 750 in August 1955 when it was sent with 'Twin-set' railcar RM 100, a EE D^F class locomotive, and a newly arrived Drewry D^SB class shunting locomotive to the Wanganui Industrial Fair. Shortly after the class took over workings in the Wairarapa area following the completion of the Rimutaka Tunnel and also the Murupara Branch from the older D^E class. These locomotives usually worked in multiple as they were relatively low-powered, although they did occasionally run on their own.

With the arrival of enough D^A class locomotives in the North Island, the D^G locomotives from the North Island were transferred progressively south with the introduction of the rail ferry GMV Aramoana in 1962. As a result, the D^H class locomotives were converted to D^G class standards in 1968 and received the D^G classification, allowing the D^H classification to be re-used in 1978.