Over The Southern Alps via Arthur’s Pass

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By the early 1920s, both English Electric and Metropolitan Vickers were very successful in wining contracts around the world, mostly in the British Colonies.  In the far east, English Electric had won major orders in Japan and New Zealand, whilst Metropolitan-Vickers had been awarded contracts to supply locomotives for the first main line electrification project in South Africa.

 

Furthest away from home, the New Zealand electrification scheme was a “comprehensive contract”, awarded to English Electric, for the conversion to electric traction of the line from Arthur’s Pass to Otira on the South Island.

The contract involved the installation of catenary through what was at the time, the longest railway tunnel in the British Empire. The tunnel, 5.5 miles long, on a ruling gradient of 1 in 33, was hewn out of the solid rock, beneath Arthur’s Pass in the Southern Alps. The route itself was very important, linking two of the South Island’s provinces, Canterbury and Westland, and the towns of Christchurch and Greymouth.

Work was begun on the Trans-Alpine route by the New Zealand Midland Railway Company in 1887, with private finance, but was taken over by the Government in 1895, after the railway company’s plans came to grief. The plan for this Midland Main Line was for steam operation, but the Arthur’s Pass section was the major challenge in the final connection.

Construction work was difficult and slow in parts, with men, horses, picks, shovels and very little machinery, and the most difficult section was over Arthur’s Pass

The route would carry heavy traffic, and the ascent over Arthur’s Pass was to have adopted the Abt Rack system, but this was clearly not a suitable option for this main line.

By 1900, the line from the West Coast to Otira had been completed, with contractors John McLean & Son were awarded a contract in 1907, to create the Otira Tunnel under the Southern Alps, and were allocated 5 years to complete the work. The project was dogged by labour troubles, and the government was petitioned for help, following strikes, disputes and difficulties during construction work. The Public Works Department took over the work, and despite the First World War, work continued, with the tunnel breakthrough taking place in 1918.

English Electric’s contract for the electrification of the “Arthur’s Pass” section of the route was one of the company’s earliest “comprehensive contract” projects, and in addition to the overhead catenary, and locomotives included a power station at Otira. This impressive project to complete this Trans-Alpine route was finally opened throughout on 4th August 1923, some 37 years after it was first proposed.

Track & Overhead

A view of the electrified section, showing the different types of contact wire support.

Overall, equipment provided by English Electric included;

  • 5 complete, 720hp, 50-ton Bo-Bo electric locomotives.
  • 1 complete, 400hp, Bo-Bo battery locomotive.
  • 1 steam generating station, with two 1,200kW, 1,650V d.c. turbo-generator sets.

The overhead line equipment also provided by English Electric, with the conductors energised at 1500V d.c. This was, at the time a common standard for the early main line schemes – and according to the company’s publicity “ …no other system than electric haulage was seriously considered”.  The fixed structures of the project included ‘double catenary’ in the open, and ‘single catenary’ through the Otira Tunnel. The conductors were supported in the open on wooden poles, with insulators attached to angle iron brackets, with more complex girder structures in stations and yards.

Steam traction was the order of the day on either side of “Arthur’s Pass”, with electric traction over and through the Otira Tunnel. The company also supplied five electric locomotives, which came to be the “E0” Class Bo-Bo design for passenger and freight duties, together with a battery locomotive for inspection and maintenance work.

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This photo taken in 1952, shows the 720hp E0 class locomotives still hard at work on mixed traffic duties on what was one of the first “composite contracts” for the 3ft 6ins gauge.               Photo: Author’s Collection

Locomotives were Bo-Bo double-ended types, rated at 720hp for those in use on the main line, and a single 400hp battery locomotive. The latter had 50hp traction motors, driving the wheels through single reduction gearing, using a ratio of 15.83 to The more powerful 720hp types, had four 179hp motors, with force ventilation, and connected permanently in series, as two pairs of motors. The tractive effort produced was 14,200 lbs at the one hour rating of the traction motors.

NZ Locos - dimensions table

These ‘box cab’ locomotives, with their twin, roof mounted pantographs used the Westinghouse air brake, and a rheostatic brake, where the electrical energy of the motors was dissipated as heat through banks of resistances. The reason why regenerative braking systems were not employed – although it was considered – was due to the fact that the power station was there purely to supply power to the railway, there being no other load to share any regenerated energy that might otherwise be fed back into the line.

The English Electric locos were still in use on this line until 1969, and one of the class has been preserved by the Canterbury Railway Society., and restored to working order in 1977, and carries its original running number E3.

NZR_EO_3_at_Ferrymead

The preserved English Electric loco No.3 at Ferrymead.
Photo courtesy Yak52fan – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6938570

The success of this first scheme also resulted in the electrification of the seven miles long, suburban section of the same route, between Christchurch and the port of Lyttelton, which again involved a ‘comprehensive contract’. English Electric was awarded another ‘ comprehensive contract’ in 1929 for this work, including the tunnel section of the line to Lyttelton, the chief port of the province of Canterbury.

 

Here again, English Electric supplied rotary convertors for the substations, but this time the principal source of power was the hydro-electric station at Lake Coleridge. Six 1,200hp Bo-Bo locomotives were supplied, with power equipment similar to that installed on the Arthur’s Pass locomotives, with the English Electric Co.’s camshaft control system. The introduction of suburban services over the line from Christchurch to Lyttelton was completed in February 1929.

Further Reading:

EE No.54

Useful Links:

Otira Tunnel – Midland Railway

Rail Tunnel Pierces the Southern Alps

Tranz Alpine

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