Lapstone Zig Zag
| Knapsack Viaduct | |
|---|---|
 |
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| Coordinates | 33°45′33″S 150°38′24″E / 33.759248°S 150.639950°E |
| Crosses | Knapsack Gully |
| Heritage status | Heritage listed |
| Characteristics | |
| Material | sandstone |
| Total length | 388 feet (118 m) |
| Height | 120 feet (37 m) |
| Longest span | 5 of 55 ft |
| No. of spans | 7 |
| History | |
| Designer | John Whitton |
| Constructed by | W. Watkins |
| Construction start | 1863 |
| Construction end | 1865 |
| Opened | 1867 |
The Lapstone Zig Zag was a zig zag railway built near Lapstone on the Great Western Railway of New South Wales in Australia between 1863 and 1865, to overcome an otherwise insurmountable climb up the eastern side of the Blue Mountains. The ruling grade was already very steep at 1 in 33 (3%). Another of the early plans 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 colony of New South Wales at the time. The track included a now abandoned station called Lucasville which was built for the Minister for Mines, John Lucas who had a holiday home nearby.
The rail route across the mountains extended as far as Wentworth Falls (then called "Weatherboard") by 1867 but the Lapstone Zig Zag, which included Lucasville station, soon ran into problems: the length of the top points and bottom points limited the length of trains and the single track meant that trains travelling in opposite directions had to stop at crossing points. The first crossing point after Lapstone Zig Zag was at Wascoe's Siding at what is now Glenbrook. The single track would contribute to a fatal accident at Emu Plains in 1878 where eastbound and westbound goods trains collided. A deviation including a tunnel was built around 1890 to replace the zig zag, but it too experienced problems as it was built at the same too steep a grade causing the locomotives to slip, and smoke became a problem for uphill trains. The building of the tunnel is the subject of Arthur Streeton's famous painting Fire's On.
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