NZR DG Class - Rebuilds

Rebuilds

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, CME 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 the 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 two, 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 sheetmetal 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 programme 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.