Lapstone Zig Zag
Lapstone Zig Zag
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Lapstone Zig Zag

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Lapstone Zig Zag

The Lapstone Zig Zag was a zig zag railway built between Emu Plains and Blaxland stations on the Main Western Line of New South Wales in Australia. Constructed between 1863 and 1865 to overcome an otherwise insurmountable climb up the eastern side of the Blue Mountains, the zig zag and associated Knapsack Viaduct, a sandstone arch viaduct, were designed by John Whitton, Engineer-in-Charge of New South Wales Government Railways, and were built by William Watkins. The zig zag was listed on the Blue Mountains local government heritage register on 27 December 1991; while the adjacent Knapsack Viaduct was listed on the New South Wales Heritage Database on 2 April 1999. The Lapstone Zig Zag was the world-first Zig Zag constructed on any main-line railway.

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-kilometre-long (1.9 mi) tunnel, but this was beyond the resources of the colony of New South Wales at the time. The track included the Knapsack Viaduct and the subsequently abandoned Lucasville station, opened in 1877.

The zig zag closed in 1892 when the Main Western line was diverted via the Glenbrook Deviation and subsequently sections of the line were repurposed as the Great Western Highway, and later use as a walking track.

The contract to build this railway from Penrith as far as Valley Heights, which included building the Knapsack Viaduct and the Lapstone Zig Zag, was awarded to William Watkins in March 1863 but was completed eighteen months behind schedule in December 1865. It opened for traffic in 1867.

Once the westbound train had crossed Knapsack Viaduct, it entered the Bottom Road of the Zig Zag. There were points where the Middle Road cut backwards and sharply upwards to form the middle stroke of the Z. Beyond the points, Bottom Road extended an additional 162 metres (532 ft) to a dead-end. It was in this area that the train stopped before it reversed direction to climb Middle Road. Similarly at the junction of Middle and Top Roads, Top Road continued some distance to buffers on the edge of Knapsack Gorge. Here the train again reversed its direction to resume the journey over the Blue Mountains. Lucasville Station was completed in 1877 on the extension section of Top Road. In 1886 the line of the Top Road extension was remodelled with a new parallel, more steeply sloped line to the west. Both of the lines of the Top Road extension are clearly legible.

The line of track (now without rails) goes through well executed rock cuttings on the standard walk along Top Road from Knapsack Street and Skarratt Park. There is a pleasing stone culvert to the south of Lucasville platform. Lucasville station was built in 1877 for the Minister for Mines, John Lucas who had a holiday home nearby. The culvert, which is still in operation, utilises a rock-cutting on the west side to divert run-off water deep under the track in a square channel constructed of stone blocks. The water then runs down a steep gully to the east. To the west of the Upper Road there is a series of low sandstone terrace walls which probably marked the boundary between Lucasville estate and the railway. The Zig Zag is largely surrounded by bushland, interspersed with impressive views east to Sydney. The setting provides a striking sense of the nineteenth-century journey over the mountains as the traveller was entering into a wilderness. At the southern entry to the Top Road of the Zig Zag, at the end of Knapsack Street, there is a gate to inhibit vehicle access. Just beside this gate, on the northern side, there are four surviving sleepers and metal spikes, all that survives from the original railway track.

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 station.

The Lapstone Zig Zag was the first Zig Zag constructed on any main-line railway anywhere in the world. The idea on which Whitton built came from the Indian railways. A friend of his, Solomon Tredwell, had in 1859 started the construction of half a Zig Zag (with a reversing line and stone viaducts) at Bhore Ghat on the Bombay to Poona line. Although Tredwell died in 1859, his widow saw the half Zig Zag to completion in 1863, employing 42,000 men, and this feat was reported at some length in The Sydney Morning Herald on 3 July 1863. Whitton knew of the conquering of the Bhore Ghat, which posed problems very comparable to the Lapstone Monocline, both from personal and public communications. The way in which he adapted the Indian experience into a full Zig Zag, approached over an exquisite, and very cheap, sandstone viaduct, was a substantial feat in world terms of railway engineering.

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