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LAKE MARGARET WOODEN CONDUIT LINE

The wooden pipe line connects to one of two 43 foot outlet pipes directly in front of the dam and on to the pressure pipes at a distance of 7150 feet from the dam. Its alignment closely follows the contour of the hillside with all its curvatures, the minimum radius used being 50 feet. The pipe however descends in one plane without hollows, ie it lies on a steady grade. The total fall is 50 feet. This wooden pipe is cheaper than a metal pipe and, as far as life is concerned, the indications are that it will last as long. It was certainly cheaper to instal at such an out of the way place. The pipe is not subject to repairs like a wooden race or flume. The wooden pipe enables every foot of head between the lake mouth and the lower termini of the pressure pipes to be utilised. Maximum volume of water delivered is 45 cubic feet per second.

The wooden conduit line is of the continuous stave construction. It is formed of 30 staves of variable length around the circumference and has an internal diameter of 4 feet. The staves consist of well seasoned Douglas fir imported from America, free from all blemishes, 1¾ inches thick by 6 inches wide. Machined all over, with a V grooved side joint and a butt joint at the ends where a thin strip of metal is drive into each stave. The staves are held in place by mild steel bands of various diameters encircling the pipe, viz, e inch, ¾ inch and f inch, so spaced as to give an even factor of safety throughout the pipe and capable of being tightened up or loosened by screw ends. These bands are placed only a few inches apart, never more than six inches. Structure is thus practically a tube made of separate steel bands, or circular bolts, with a continuous wooden wall filling. The stays are purposely kept quite thin, for the safety of the pipe depends not upon the thickness and strength of the wood, but on the number and size of the steel bands and the thinness of the staves contributes to the life or preservation of the wood. It is expected that the wood shall permit of the transpiration of a small amount of water, which thus keeps the fibre in a healthy state. Heavy, stout thicknesses of staves would lead to decay. The staves were all faced by a special machine driven by the temporary hydro-electric plant, at the power house site and the staves and bands delivered into position off the high level tram. The pipe was thus put together in place, stave by stave and, working from both ends, [by the] Australia Wood Pipe Company of Sydney, under contract.

Though a novel undertaking in these dimensions in this part of the world, it appears to be an unqualified success. It is not fastened down but simply lies on the bed prepared for it on the ground, or bearers, or on elevated trestles and holds its position immovably owing to its great weight.

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