Raurimu spiral
The Raurimu Spiral is a single-track loop construction with roundabouts on the North Island Main Trunk Railway of New Zealand , which connects the cities of Auckland and Wellington . The route overcomes a height difference of 132 m, contains two tunnels (384 m and 96 m long) and three hairpin bends .
background
During the construction of the central section of the North Island Main Trunk Railways between Auckland and Wellington, the problem arose that between Raurimu Flat and the central plateau at the National Park a height difference of 218 m had to be overcome over a distance of about 6 km as the crow flies. At the time of the survey in the 1890s, the area consisted of tall, dense rainforest. A direct connection would have meant a gradient of 1:24. For a long time a 19 km long alternative route was pursued, which would also have required nine viaducts and a gradient of 1:50.
construction
The solution finally implemented was developed by the engineer RWHolmes in 1898. He suggested the spiral route with two tunnels and an average gradient of 1:52. Long parts of the route are, however, also laid out with a gradient of 1:50. The lower hairpin curve has a radius of 198 m, the upper curves and the roundabout a radius of 200 m. Overall, the route extends the distance between Raurimu and the National Park to around 11 km.
The spiral begins in Raurimu with a 180 ° bend to the left, followed by two sharp right bends, then the route goes through the two mentioned tunnels. In a complete roundabout to the right, the longer tunnel is then crossed before the route continues to climb the plateau. After another two kilometers, there is a sharp right and a left curve.
Worth knowing
Branching off from State Highway 4 in Raurimu to the east is the exit to a lookout point with an elevated stand , from which part of the facility can be seen.
literature
- Churchman, Geoffrey B .; Hurst, Tony: The Railways Of New Zealand - A Journey Through History , HarperCollins Publishers (New Zealand) (for 1st edition 1990), transpress New Zealand Wellington (2nd edition 2000), ISBN 0-908876-20-3 . (Page 124)
Web links
- Route map
- Terry's Train Trax . Archived from the original onJanuary 22, 2009; accessed on September 7, 2014(English, original website no longer available; (aerial photo and route sketch)).
Coordinates: 39 ° 7 ′ 15 ″ S , 175 ° 24 ′ 5 ″ O