Cougal Spiral (railway)
Up Brisbane Mail crosses over No.1 Spiral Tunnel
|Other name(s)||Border Tunnel
Border Loop Spiral
|Line||North Coast Railway|
|Location||Richmond Gap connecting New South Wales and Queensland, Australia|
|Length||A series of three tunnels:
The Cougal Spiral is a heritage-listed single track railway tunnel and spiral feature of the North Coast Railway in Australia that connects New South Wales with Queensland through Richmond Gap. The railway lines needs to climb at a steady ruling gradient from Kyogle to the summit at a tunnel at the border between the two states. The border is also at the watershed.
Climbing almost non-stop at the ruling grade of 1 in 66 or 1.5% (compensated) the line has almost continuous curves of 240 m (790 ft) radius. Near Cougal, the alignment finally runs out of valley, and has nowhere to go. Fortunately a convenient hill allows the line to circle back on itself so that it climbs 30 metres (98 ft) without having to make any forward progress. Soon after the Border Tunnel under the watershed is reached, and the line descends on the other side. The spiral has two short tunnels, one where it passes under itself, plus another through a small spur in the hillside.
The tunnel at the border summit is approximately 1,600 metres (5,200 ft) long, broken up into three separate tunnels. A lower summit, perhaps without the spiral, would be possible with a considerably longer and more expensive summit tunnel, with the possibility of problems with fumes for both the original steam locomotives and the replacement diesel engines.
- "Cougal To Border Loop, Railway Spiral and Landscape". New South Wales State Heritage Register. Office of Environment and Heritage. Retrieved 11 September 2017.
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