New Zealand EW class locomotive

New Zealand EW class locomotive
EW 1805 with DC 4611 approaching Paekakariki, 21 August 2005. The EW had been brought for preservation and was later towed to Plimmerton.
Type and origin Power type Electric Builder English Electric/Robert Stephenson and Hawthorns, United Kingdom
Specifications Configuration: ​  • UIC Bo-Bo-Bo Gauge 1,067 mm (3 ft 6 in) Length 18.9 metres (62 ft 0 in) Adhesive weight 76 tonnes (75 long tons; 84 short tons) Loco weight 76 tonnes (75 long tons; 84 short tons) Electric system/s 1500 V DC overhead lines Current pickup(s) Pantograph Traction motors 6
Performance figures Maximum speed 97 km/h (60 mph) Power output 1,340 kW (1,800 hp) Tractive effort 104 kN (23,000 lbf)
Career Operators New Zealand Railways Class EW Number in class 7 Locale Wellington region First run July 1952 Last run November 1987 Disposition 5 scrapped 2 preserved

The New Zealand E^W class locomotive was a class of electric locomotive used in Wellington, New Zealand. The classification 'E^W' was due to their being electric locomotives allocated to Wellington. For two decades until the advent of the D^X class they were the most powerful locomotives in New Zealand.

The E^W class were first ordered by New Zealand Railways from English Electric through their New Zealand agents Cory-Wright & Salmon in 1951 as a replacement for the earlier E^D class electric locomotives on passenger duties. It was felt that the E^D class was not suitable for this, and so English Electric was commissioned to build a twin-section articulated electric locomotive for use on the Wellington 1.5kV DC electrified system.

The new E^W class was the first locomotive class in New Zealand to utilise the Bo-Bo-Bo wheel arrangement, which would subsequently be copied on the Mitsubishi D^J class and Brush EF class. However, the E^W class was different in that the central Jacobs bogie was placed under the articulation of the two body halves with limited sideplay, whereas the D^J and EF classes have a single fixed body with sideplay in the central bogie.

During this time a proposal was made about building a Bo-Bo+Bo-Bo electric locomotive, which would essentially be a pair of E^W class locomotives permanently coupled together as one locomotive. This was initially classified E^WO, but later received the classification E^X. However, this did not proceed as the CME felt that it would not be possible to re-engineer the E^W class, which had been designed to work in Wellington, for the 1 in 33 gradients between Arthur's Pass and Otira. The locomotives would also need major alteration such as the fitting of rheostatic brakes, as used on the E^O class, and multiple-unit equipment.