NZR DG class

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New Zealand DG and DH class
Pair of reds.JPG
Two DG class locomotives at Dunedin in the early 1980s.
Type and origin
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 3 in)
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) DH
Locomotive 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)
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
Number in class 31 DG
11 DH
Number(s) 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 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 DF class were changed to 42 DG class locomotives, being a half-sized 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 they were fitted with adjustable bogies that allowed a higher maximum axle weight and tractive effort.

The first regular outing by a DG class locomotive was that of DG 750 in August 1955 when it was sent with 'Twin-set' railcar RM 100, a EE DF class locomotive, and a newly arrived Drewry DSB 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 DE 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 DA class locomotives in the North Island, the DG locomotives from the North Island were transferred progressively south with the introduction of the rail ferry GMV Aramoana 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.

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.


In the late 1970s, the DG class was reaching the end of its designated working life with a litany of problems:

  • Mechanical and electrical failures were occurring on a regular basis.
  • The EE 6SKRT engine blocks were cracking due to premature wear.
  • Working conditions on the locomotives were known to be poor as well. There were no crew amenities, and the cabs were draughty.

In an attempt to modernise the DG class and extend the working lives of the locomotives, Chief Mechanical Engineer Graham Alecock was requested to prepare a plan to equip the DG class locomotives with new cabs that would be more crew-friendly and improved equipment. The decision was taken to rebuild DG 760, then due for an overhaul at Hillside Workshops as the prototype for the rebuilds, which would be dubbed the 're-cabs' by enthusiasts.

The new cab was designed 'in-house' by NZR, who then contracted NZR's Westport Workshops to build them on Hillside's behalf. The cab itself was larger than the original DG cab, which required the low nose at the front to be shortened. The whole assembly had a pronounced box-like shape, with 45° angles to the cab roof and low nose. The new cab featured four windscreens to the original three, while the low nose had a larger doorway to access the new Westinghouse 26L air-brake equipment and also gave provision for a short walkway on either side of the nose.

Mechanically, the locomotive's front traction motor blower was shifted to a position above the main generator, while new thermostat valves were fitted in an attempt to prevent the overheating problems that had plagued the locomotives under load. The original Westinghouse A7EL brake system was replaced by the more modern 26L system, actuated by a new push-button console in the cab. The traction motors were also upgraded, while welding repairs were conducted on the 6SKRT engine blocks. Several blocks were later sent to America for repairs using the Metalock treatment; this was later deemed to be a failure as the blocks again cracked and the Metalock treatment was seen as a waste of money.

The rebuilt locomotives also underwent several minor changes. Steps were fitted to the rear of the locomotives to allow access to the roof, external door handles and step-ladders were fitted to the middle set of engine-room doors, and an automated handbrake system was fitted. The locomotives also had front ladders fitted to allow access to the cab windows, some of which were integrated into the sheet metal profile edge from the locomotive frame to the leading headstock. Both horns were relocated to the front of the cab, although the rebuilt DG 760 had three - two forward facing on the cab front, with one behind the cab.

DG 760 was released from Hillside in August 1978 and was placed into service as the first of an eventual ten rebuilds to be completed between 1978 and the end of the program in 1980. While the LEA and EFCA were pleased with the cab design which took into consideration their input from the early design phases, the locomotive was perhaps not as mechanically successful as it should have been. Traction motor and engine problems still occurred, as well as occasional electrical faults. However, the locomotives were put into service hauling freight trains on the Main South Line and occasionally the Midland Line. Although the new cabs were designed with the Otago Central Railway in mind, very few of the re-cabbed locomotives ever worked this line.

Ten further DG class engines - nine built by Vulcan Foundry and one by RS&H - were given 'A'-grade overhauls to work as trailing B-units for the rebuilt locomotives. These locomotives did not receive new cabs, and as such were not to be driven in regular service although photographs from this time show these locomotives were sometimes driven in regular service rather than turn a re-cabbed locomotive around. A number of other locomotives of this type also received the updated Westinghouse 26L brake system and NZR designed push-button control stand.

The class continued to suffer from reliability issues brought about by electrical and mechanical failures, and were later prohibited from running in multiple with the Mitsubishi DJ and General Motors DF locomotives, although they did sometimes run with the DJ class past this time. It was decided to start withdrawing those locomotives that had not been overhauled to provide parts for those that had, and so the first to be withdrawn, DG 765, was withdrawn on the fact it had a good engine block.

By 1983, most of the original-cabbed DG class had been withdrawn, while the re-cabbed locomotives continued in service until they either suffered a mechanical failure, required major repairs or were withdrawn serviceable and placed in storage. On 28 August 1983, NZR operated a 'Farewell to the DG Class' excursion between Christchurch and Arthur's Pass on the Midland line. Hauled by recabbed DG 2007 and 'slave' unit DG 2468, the first and last DG class locomotives respectively, the excursion marked the end of the original DG class in regular service. The following month, DG 2007 failed when it threw a con rod through the engine block and was placed in storage, while DG 2468 was sold to the fledgling Weka Pass Railway shortly after.


With the phasing out of the DG class in the early 1980s, several locomotives were purchased for preservation. The first to be purchased were DG's 2232 and 2468 (DG's 770 and 791) by the Weka Pass Railway in 1983. Shortly after, the Diesel Traction Group purchased DG 2255 (DG 772) and moved it to their operating base at the Ferrymead Railway, while Roger Redward purchased DG's 2376 and 2451 (DG's 783 and 790) for his proposed Southern Rail museum in Christchurch. In addition, NZR considered adding DG 2445 to its Heritage Fleet at the time. However, 2445 had a cracked engine block, which did not fit with NZR's policy of operating Heritage Fleet locomotives. Due to the extent of the cracking, it was decided to be uneconomic to repair, and so the locomotive was scrapped by Sims Pacific Metal Industries in Dunedin.

Following Roger Redward's death in 1988, NZR decided to re-possess all of Redward's collection held on NZR property as Redward had failed to make several rent payments. Although owners were sought for the vehicles, no home could be found for DG 2451, and so NZR sold it to Sims Pacific Metal Industries who broke it up in their Sockburn yard in March 1990. DG 2376 was sold in 1988 to the Weka Pass Railway, who were at the time seeking spare parts to maintain their two locomotives, and trucked to their Waipara yard where it was gradually stripped of most of its useful parts.

DG 2255 was restored as DG 772 in 1988 and participated in the 'Ferrymead 125' event, during which it hauled a short excursion train with DE 511 to Springfield and return. It remained in active service until the early 1990s, during which time it covered for Weka Pass' DG 791, which had cracked the bolster on its leading bogie and had been removed from traffic to allow the better bolster from DG 2376 to be fitted in its place. After this it became inactive until 2005, when the Diesel Traction Group began its restoration. This was completed in 2008; as part of this, the locomotive's Westinghouse A7EL brake system was replaced by the newer 26L system, and it was fitted with ditch lights, a VHF radio and an events recorder to allow it to run on the main line.

In 2005, Weka Pass decided to sell the remains of DG 2376 with the condition that it was removed from Waipara after purchase. The locomotive was subsequently purchased by Darryl Bond and Evan Batchelor, who had the derelict locomotive moved to Ferrymead, where it was planned to restore the locomotive. The locomotive's front bogie (fitted with the cracked bolster ex-DG 791) has since been repaired, the body largely derusted, and parts have been acquired to begin to restore the locomotive to service in the later International Orange livery, which 2376 never carried in service. In late 2013 the locomotive was moved to Oamaru.

At present, DG's 770 and 791 are in regular use by the Weka Pass Railway. They were returned to their original numbers in 1988, at which time they had the railway's name painted to the rear of the cab door, although they retained their 'International Orange' livery. In 1999, prior to the re-opening of the line from Herbert's Crossing to Waikari, both were repainted in the original NZR Red with Larch Yellow nose stripes. The two locomotives are regularly used from late November to early March when fire bans are in place, or to haul occasional work trains.

Rietveld's DGs[edit]

The Dunedin machinery dealers W. Rietveld were contracted by New Zealand Railways in 1983 to scrap the re-cabbed DG class locomotives, which were then stored at Dunedin. These locomotives were largely unserviceable due to mechanical failures or had been laid up with the arrival of more modern motive power. Several of these locomotives had been lifted by NZR in order to gain access to their EE 525 traction motors, which had been sold to the National Federation of Railway Societies for distribution to other groups who owned DG class locomotives.

Rietveld used the former sidings at Pelichet Bay to house the withdrawn locomotives while they were stripped of all useful parts. The hulks would then be forwarded to Sims-PMI for scrapping at their Dunedin premises. The first four locomotives to be moved to Pelichet Bay were numbers 2036, 2140, 2105, and 2347. They were followed several months later by numbers 2007, 2290, 2111 and 2439. The last two, DG 2128 and DG 2330, remained at Dunedin Locomotive Depot for a time after that as Rietveld hoped to sell them to an overseas concern. This did not eventuate, and the two locomotives were towed to Pelichet Bay for stripping - the last two re-cabbed DG's to exist.[1]

Several of the unique cabs from these locomotives were not scrapped but instead removed intact by Rietvelds, who in 2001 held several at their Abbotsford reclaim site, including that of DG 2007. The cab of DG 2140 was purchased by Darryl Bond, part-owner of DG 2376.

Class register[edit]

Key: In service Out of service Auckland Transport service Preserved Overhaul/Repair 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 Preserved, Weka Pass Railway.
DG 771 2249 May 1956 Scrapped
DG 772 2255 August 1956 Preserved Preserved, Diesel Traction Group.
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 Preserved privately, stored in Oamaru.
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 Preserved, Weka Pass Railway.


Further reading[edit]

  • "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[edit]