You won’t find many of these in Australia. In fact, I think there might be only two of them.
So, what am I talking about?
Trains. And railways.
In the days of the steam train, locomotives didn’t have the power to conquer steep climbs. There needed to be work-arounds. The most common one was to reroute the track to avoid an otherwise insurmountable range. An alternative – not always applicable – was to construct a spiral around the range that allowed the track to gain the altitude needed at a reduced rate of incline the locomotive could manage. Sort of like a spiral staircase.
The two railway spirals with full 360⁰ loops are on the Sydney to Brisbane single track line through the Border Ranges on the New South Wales side of the Queensland-New South Wales border; and on the Melbourne to Sydney double track line between Junee and Cootamundra just north of the village of Bethungra, but it’s only the “up line” heading to Sydney that has the spiral.
The Bethungra Range
Between Junee and Cootamundra in southern New South Wales, trains on the then single track between Sydney and Melbourne were subjected to long delays as those travelling north had to be helped up the 1 in 40 incline of the Bethungra Range by an extra locomotive kept on stand-by at Bethungra. The need for more efficient rail transport on this crucial line was more keenly recognised with the flurry of war time movement of personnel and goods. Hence, in the early 1940s a new “up line” to Sydney was constructed making us of the geography to build an 8.9km spiral deviation around a hill that added about 2km to the distance travelled by the uphill trains but reduced the incline to 1 in 66.
Construction of the Spiral
The construction of the spiral was quite an engineering feat. Cuttings of 27m deep had to be blasted through the granite hill. Several rock falls over ensuing years hindered use of the spiral. In January 1994, the spiral line closed for a four-month rebuild which saw the cuttings widened.
Description of the Spiral
Rather than spend time describing how the spiral works – it’s a bit more complicated with a double track – I’ve made this short video that explains it all.