New Zealand DSC class locomotive

The New Zealand DSC class is a heavy shunting locomotive used throughout New Zealand. The class was built in seven batches, the first 18 locomotives being built by British Thomson-Houston of the United Kingdom, with the remainder being built by New Zealand Railways.

The class is widely used in both the North and South Islands of New Zealand, mainly for heavy yard shunting, although some members of the class have been used for local mainline shunting services. All members of the class are now fitted with shunters refuges, and most are fitted with remote control capabilities.

Design and entry into service

In the late 1950s, NZR needed a suitable heavy shunting locomotive that produced more power than the existing D^S and D^SA class locomotives and would be suitable for replacing the B^B, C, and W^F class steam locomotives. In 1959, an order was placed with British Thompson-Houston in association with the Clayton Equipment Company for eighteen centre-cab shunting engines with a horsepower output of around 420 hp.

The new locomotives, allocated road numbers D^SC 400-417, entered service in 1959-60 and were allocated to Auckland and Frankton Junction (Hamilton). For a time in 1962, D^SC 402 was dispatched to Picton to shunt the NZR road/rail ferry MV Aramoana until newly constructed Addington D^SC 418 arrived to take over, allowing 402 to return north.

The BTH locomotives were powered by two Rolls-Royce C6SFL 210 hp diesel engines connected to BTH generators, which were in turn coupled to four BTH traction motors, one to each axle. They were not entirely without trouble, though, with issues arising with the airbrakes and spare parts for the diesel engines among others. However, once this was resolved, the class settled down to work reliably in their intended role.

Two further orders were placed with the NZR Addington and Hillside Workshops in the 1960s, with production running from 1962 to 1967. The NZR-built locomotives were different in that they were powered by two Leyland UE902 diesel engines producing 210 hp, and had electrical equipment built by Associated Electrical Industries Ltd (AEI), which had purchased BTH earlier. Again there were various troubles, this time more to do with the mechanical components and compatibility on later batches.

Re-engining

In the late 1970s, NZ Rail decided to undertake a re-engining programme for the D^SC class. Due to design differences, it would not be possible to use the same type of diesel engine across all locomotives, and so two different types were selected:

• All BTH locomotives would be repowered with the Rolls-Royce C6TFL diesel engine.
• All NZR locomotives would be repowered with the Cummins NT855 diesel engine.

The process was spread out from the late 1970s into the early 1980s. As part of this, some locomotives were repainted in the International Orange livery but with their pre-TMS numbers instead of the later TMS numbers. As a result of this, the locomotives were equipped with new radiator header tanks which were mounted behind the radiator on top of the engine hoods in a 'north-south' alignment. Later the tanks were relocated to an 'east-west' alignment.

Fitting shunter's refuges

In 1989, DSC 2406 was trialled as the first shunting locomotive to be fitted with shunter's refuges at either end of the locomotive. New recessed steps were fitted at either end of the locomotive frames with a vertical hand-rail on the running-board proper. The locomotive's engine hoods were not shortened at the time.

This modification was successful, but it was noted that the engine hoods were a potential constraint. All further DSC class locomotives equipped with the refuges had their engine hoods shortened by 500mm, necessitating the relocation of the radiator header tanks to their present 'east-west' alignment.

This modification was subsequently made to all DSG, DSJ, and DH class locomotives as well as DAR 517. None of the BTH-built DSC class locomotives were fitted with these refuges and several NZR-built examples did not receive them either, due to withdrawal before they could be fitted or by dint of being used for other purposes.^[1]

Withdrawal and preservation

As of May 2016, 38 units have been withdrawn from service. As apart of the program of the New Zealand Railways Corporation to rationalize the locomotive fleet in the late 1980s, all of the British Thomson-Houston built locomotives, along with three NZR builds, were withdrawn between February and November 1989. All, besides 2067, were scrapped at the Otahuhu Workshops and Hutt Workshops in 1990. DSC 2067 was given a reprieve when it was sold to New Zealand Milk Products (later subsumed into Fonterra) to shunt their Whareroa milk factory. In 2007 the locomotive was sold to the Alliance Group Limited to shunt at their Pukeuri freezing works on the outskirts of Oamaru.

In 1990, 2231 and 2637 were laid up due to accident damage. Between 2001 and 2007, 11 units were laid up surplus to requirements, or due to accident damage. Seven of them were scrapped. The two of the remaining four were sold for industrial work and the other two were sold for preservation. The ones that were sold are 2421, which was sold in 2002 to the Alliance Group to shunt at their Lorneville freezing works near Invercargill, and 2257, which was sold to Ravensdown Fertiliser in 2007 and is now stored at their New Plymouth depot. The other two that was sold into preservation, were 2584 that was sold in 2003 to the Waitara Railway Preservation Society for use on their passenger trains between Waitara and Lepperton. The other, 2759 was sold to Ian Welch in 2002 for the Mainline Steam Heritage Trust and is used as the depot shunting locomotive at Plimmerton along with Bagnall TR 534.

In between 2007 and 2008, 2244, 2285, 2434 and 2830 were laid up because of being surplus to requirements. In 2014, 2244 was overhauled and released back into service. In 2015, 2338 was also laid up. All four are now stored at Hutt Workshops.

Class register

References

External links

• NZ Rolling Stock - Preserved NZR diesels