- NZR DG class
-
NZR DG / DH class 
Two DG locomotives at Dunedin in the early 1980s. Power type Diesel-Electric Builder English Electric and Vulcan Foundry / Robert Stephenson & Hawthorn, United Kingdom UIC classification A1A - A1A Length 14.7 metres (48 ft) Weight on drivers 46.6 tonnes (45.9 long tons; 51.4 short tons) DG
48.4 tonnes (47.6 long tons; 53.4 short tons) DHLocomotive weight 70 tonnes (69 long tons; 77 short tons) Prime mover English Electric 6SRKT Mk 2 Engine RPM range 850 rpm Traction motors Four EE 525 / 2A Cylinders I6 Cylinder size 254 mm × 305 mm (10.0 in × 12.0 in) Top 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) DHNumber in class 31 DG
11 DHNumber 750 - 791 (original)
2007 - 2497 (TMS)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 used on New Zealand's national rail network, built by English Electric.
Contents
Introduction
Due a change in government dieselisation strategy 21 of the original order for DF class were changed to 42 DG class locomotives, being a 'half' version of the DF 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 'DH' because of their higher maximum axle weight and tractive effort. However, DG locomotives from the North Island began operating in the South with the introduction of the Aramoana rail 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 design deficiences in the engines[citation needed] and the standards of design of first-generation diesel locomotives worldwide, especially in relation to noise and crew comfort. 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.
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. Six of the recabbed locomotives were members of the Robert Stephenson & Hawthorn built batch. At the same time, nine of the Vulcan Foundry built batch and one of the Robert Stephenson & Hawthorn batch were overhauled to work as slaves (B units) with the recabbed locomotives; they did not receive new cabs and thus were not driven in regular service.
However, the class continued to be plagued by operational problems[citation needed] and were all withdrawn from service at the end of 1983, the slave units being written off first, followed by the recabs. Recab DG 2007 and original 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. DG 2468 moved to the Weka Pass Railway soon after.
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.
Dg 772 is registered and certified for use on the National Rail Network.
Class register
Key: In service Out of service Auckland Transport service Preserved Overhaul Scrapped Original No. TMS No. Introduced Withdrawn Status Notes DG 750 2007 September 1955 February 1984 Scrapped Recabbed 1979. DG 751 2474 October 1955 November 1980 Scrapped DG 752 2036 October 1955 February 1984 Scrapped Recabbed 1979. DG 753 2042 December 1955 February 1981 Scrapped DG 754 2059 December 1955 November 1982 Scrapped DG 755 2065 December 1955 April 1980 Scrapped DG 756 2071 February 1956 November 1981 Scrapped DG 757 2088 February 1956 Scrapped DG 758 2094 January 1956 Scrapped DG 759 2105 March 1956 Scrapped Recabbed 1980. DG 760 2111 October 1956 Scrapped Recabbed 1978. DG 761 2128 March 1956 Scrapped Recabbed 1980. DG 762 2134 March 1956 Scrapped DG 763 2140 April 1956 Scrapped Recabbed 1979. DG 764 2157 April 1956 Scrapped DG 765 2163 May 1956 Scrapped DH 766 2186 August 1956 Scrapped DG 767 2192 July 1956 Scrapped DG 768 2480 July 1956 Scrapped DG 769 2226 September 1956 Scrapped DG 770 2232 June 1956 Preserved Weka Pass Railway, Waipara. DG 771 2249 May 1956 Scrapped DG 772 2255 August 1956 Preserved Ferrymead Railway, Christchurch. DG 773 2261 June 1956 Scrapped DG 774 2278 September 1956 Scrapped DG 775 2284 August 1956 Scrapped DG 776 2290 September 1956 Scrapped Recabbed 1980. DH 777 2301 August 1956 Scrapped DH 778 2318 August 1956 Scrapped DH 779 2324 September 1956 Scrapped DH 780 2330 September 1956 Scrapped Recabbed 1980. DH 781 2347 September 1956 Scrapped Recabbed 1979. DH 782 2497 September 1956 Scrapped DH 783 2376 October 1956 Preserved Stored at Ferrymead Railway. DG 784 2382 September 1956 Scrapped DG 785 2399 September 1956 Scrapped DG 786 2416 October 1956 Scrapped DG 787 2422 November 1956 Scrapped DG 788 2439 November 1956 Scrapped Recabbed 1980. DG 789 2445 December 1956 Scrapped DG 790 2451 December 1956 Scrapped DG 791 2468 December 1956 Preserved Weka Pass Railway, Waipara. References
- "NZR Locomotives and Railcars 1983". T A McGavin. New Zealand Railway and Locomotive Society : Wellington, New Zealand : 1983.
- "New Zealand Railway Diesels". E J McClare. Southern Press : Wellington, New Zealand.
- "The Life and Times of the NZR's DG Class Diesel-Electric Locomotives". P J R Dunford, New Zealand Railway Observer No.230. New Zealand Railway and Locomotive Society : Wellington, New Zealand : 1997.
External links
Categories:- Locomotives of New Zealand
- English Electric locomotives
- A1A-A1A locomotives
Wikimedia Foundation. 2010.
