NZR DG class
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| NZR DG / DH class | |
| Power type | Diesel-Electric |
|---|---|
| Builder | English Electric and Vulcan Foundry, United Kingdom |
| UIC classification | A1A - A1A |
| Length | 14.7 m |
| Total weight | 70t |
| Prime mover | English Electric 6SRKT Mk 2 |
| Top speed | 97 km/h |
| Power output | 560 kW / 750 hp |
| Tractive effort | 198 kN |
| Career | New Zealand Railways, Ferrymead, Weka Pass Railway |
| Number in class | DG: 31 DH:11 |
| Number | TMS numbers: 2007 - 2468 Early numbers: 750 - 791 |
| Locale | All of New Zealand |
| First run | 1955 - 1956 |
| Last run | 1983 |
| Disposition | 0 in service; 4 preserved |
The NZR DG and DH class locomotives were a class of diesel-electric locomotives in New Zealand. The class was introduced as an alternative to the DF class, being a 'half' version of the DF with only one cab instead of two. The South Island allocated locomotives were initially classified 'DH' because of their lower axle weight. However, DG locomotives from the North Island began operating in the South with the introduction of the Aramoana ferry in 1962. As a result, the DH class locomotives were converted to DG class standards in 1968 and received the DG classification, allowing the DH classification to be re-used in 1978.
The DG class suffered from a number of defects, mainly relating to engine overheating [citation needed]. Thus with the introduction of the DJ class in 1968 the class was usually relegated to "slave" status. The introduction of the new DF class further displaced the class.
[edit] Rebuilds
In an attempt to modernise the locomotives and extend their working lives, ten members of the DG class were rebuilt by Hillside Workshops between 1978 and 1980. The main cosmetic change was to the locomotives' cabs, which were replaced with a New Zealand Railways designed structure. Engineering changes included relocation of the front traction motor blower to a position above the main generator, removal of the A7EL brake controls in favour of a hybrid New Zealand designed push button system, upgrading of traction motors and overseas welding to address cracks in engine blocks. Minor cosmetic changes included addition of steps at the rear of the locomotive for roof access, provision of external door handles and step ladders for mid-loco engine room doors and an automated handbrake system.
However, the class continued to be plagued by operational problems and were all withdrawn from service at the end of 1983. Recab DG 2007 and old cab 2468 ran a farewell excursion on the Christchurch - Arthurs Pass section of the Midland line on 28 August 1983. This marked the end of the old cab DG service. DG 2007 suffered major failure (con rod through engine block) during the following month.
[edit] Preservation
Four locomotives have been preserved: DGs 770 and 791 at the Weka Pass Railway, DG 772 by the Diesel Traction Group at Ferrymead, and a fourth, DG 783, is owned privately and stored at Ferrymead.
