Lapstone Zig Zag
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The Lapstone Zig Zag was a zig zag railway built on the Great Western Railway of New South Wales in Australia around 1872, to overcome an otherwise insurmountable climb up the eastern side of the mountains. The ruling grade was already very steep at 1 in 33 (3%). The original plan had been to build the whole line across the Blue Mountains on a completely different route through the Grose Valley with a 3 km long tunnel, but this was beyond the resources of the state of New South Wales at the time.
The Lapstone Zig Zag, which included Lucasville station, soon ran into problems in that the length of the top points and bottom points limited the length of trains. A deviation including a tunnel was built around 1890 to replace the zig zag, but it too experienced problems as it was built at too steep a grade causing the locomotives to slip, and smoke became a problem for uphill trains.
By 1910, the line as a whole was being duplicated (made into double track) and the "rathole" tunnel was replaced on a different deviation with a gentler alignment with 1 in 60 (1.67%) grades and the Glenbrook tunnel. From then on the lower section of the track, including the historic Knapsack Gully Viaduct, was converted into a road, the Great Western Highway, the main road over the mountains until the M4 expressway replaced it in the 1980's.
The line of the old track and cuttings (including the long abandoned platform of Lucasville station), and the old Knapsack Gully bridge is now a popular bushwalking track.
[edit] References
- Full Steam Across The Mountains - Phil Belbin & David Burke - Methuen Australia 1981
- Blue Mountains Railways - William A. Bayley - Locomotion Productions 1980
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