WONDERS OF ARAPUNI.

New Zealand Herald, Volume LXII, Issue 19177, 17 November 1925, Page 11

WONDERS OF ARAPUNI.

MANY INTERESTING DEVICES.

THE NINE-MILE ROPEWAY.

ENGINEERS' HARD TASKS.

BATTLE WITH RAIN AND MUD.

If anyone doubts that this is an age of wires as well as of wireless, he had better visit Arapuni. Without yards and miles of wire and cable, whether copper or steel, the building of the great hydroelectric power plant would be almost impossible.

Among all the clever devices used at Arapuni, perhaps the most notable is the ropeway by which crushed stone for concrete will be brought from a quarry at Muku, about nine miles up the Waikato River.

When Armstrong, Whitworth and Company took the Arapuni contract they knew that no stone suitable for concrete was obtainable in large quantities within miles of the dam-site. The Public Works Department had prospected for hard stone, and reported that the nearest deposit was rather over ten miles upstream. The contractors made their own investigations on this spot, and decided that the quantity was not adequate. However, one of their men had seen a small outcrop of greywacke on a steep face a little lower down, and urged that it should be tested. The result was that underneath a heavy overburden of soft material a huge mass of excellent stone was discovered, more than sufficient for a concrete dam, 155,000 tons in weight, a reinforced concrete power-house, spillway weir, tunnel linings, and all the other appurtenances.

The problem now was how to get the stone to the dam-site. River transport would take it only part of the way, owing to rapids, and ever, then the stone would have to be hoisted more than 150 ft. to the lip of the gorge. To build a road would have cost far too much, and, besides, the river had to be crossed. So it was decided to put in a rope conveyer, and the work was entrusted to .Ropeways, Limited, a Scottish company, which has installed such contrivances in all parts of the world. How the Line Works, Operations were started last March, and after overcoming difficulties which might well have disheartened them, the engineers and workmen now have the line almost in running order. It will be working probably in a fortnight. Continuous heavy rain, and sodden, hilly country have been their worst enemies.

Short- ropeways, mostly of the.doublecable type, have been in use for years on the West Coast- coalfields, but no such system as that at Arapuni has been seen in New Zealand before. It is really a simple apparatus. The line is divided into two sections, running in perfectly straight across country, and meeting at an almost imperceptible angle. Each section consists of an endless steel rope, supported from wooden towers ranging from 15ft. to more than 100 ft. in height. 'I he rope, about lin. in diameter, is supported on large steel wheels, four on one side of a tower (the side on which the full buckets pass) and two on the other. It runs round a large wheel at each end of the line, one wheel being driven bv an electric motor and the other attached to a three-ton tension weight hanging in a pit. The buckets, holding Bcwt. of stone apiece, are suspended from the wire by a hook-like hanger, cleverly designed so that it can pass over the wheels on the towers almost without touching them.

There are two wheels on each buckethanger. These are idle when the bucket is travelling on the rope, but at the" end of the journey it is cleverly shunted on to a rail, which engages with the wheels. There is a similar rail at the loading end, and one is also used for transferring the buckets from one rope to the other at the half-way station.

Over Hill and River,

One curious thing about the ropeway is that it requires but 120 horse-power to drive it —one 60 horse-power motor working each section of line. Considering that the rope alone weighs 75 tons, while no fewer than 365 buckets, half of them loaded, can be operated at once, it is remarkable that so little motive-power is required. Ropeways have to run straight from point to point, but they take hills -and rivers in their stride with perfect ease. In the Andes one of them traverses a valley which by any other means takes three days to cross. There is nothing so bad as that between Muku and Arapuni, but one span between hilltops measures 1375 ft in a single big sweep, and another a little over 1200 ft. Five buckets, at the minimum interval of 252 ft, can be running upon the long span at, one time. The Waikato River is crossed between two of the tallest towers, one about 105 ft high. These have been made lofty so that the line will still be above water level when the dam turns the river into a lake. The ropeway is designed to deliver 40 tons of crushed stone an hour, each bucket taking just under two hours to cover the nine miles from quarry to dam. In the Eain and Mud.

The engineers and their men conquered the worst possible difficulties. To begin with they had to carry on through the winter, and a very bad winter it was. No fewer than 126 trestle towers had to be built, some of them on hilltops and treacherous faces hundreds of feet above the river* There were no roads, and the timber had to be dragged for miles from the bush over sodden clay hills, rolled down slopes, slid down wires and often man-handled into place. Many poles got themselves into gully-bottoms and other awkward places, where they simply had to be abandoned. It was an even harder task to handle the great reels of wire rope, weighing four or five tons apiece. These were dragged and rolled by all sorts of means to the least inconvenient spots, and there unwound. Some sections of the line could not be reached, and the only course was to haul two reelfuls for a couple of miles over the tower-pulleys. All transport was exceedingly difficult, but the line now stands a monument to the endurance of the men who made it.

Plant fox Stone-crushing. It may be mentioned that to splice two pieces of rope together was a day's work for eight men. The splices are 120 ft. long, and are invisible to any but an expert eye. The men employed on this work are riggers, specially trained in splicing by the engineer in charge. The thousands of bolts used for fastening the towers together were all made in the workshops at Arapuni. Power for the two sections of line is applied at Arapuni and the ha - way station respectively. Current is taken at. the latter point from an 11,UUUvolt line running out to the quarry. At Muku there is a complete plant for dealing with the stone. It is t _: von the nuarrv trucks to four crushers, driven in pairs "by two 60-horse-power electric motors The crushers can turn out 4 in. | the rv ' .'.j be m j xe d on the cliff-ecige and Cr run down chutes to the dam and tU Fo e r !S tL ek power-house, penstocks and so in way, stone will be taken across th« na nn a separate cablowsy, dumped mto trucks, and carried half .a mile or so by light railway. Sand will arrive by the reverse process.