Advantages claimed for new irrigator

Press, 10 June 1977, Page 7

Advantages claimed for new irrigator

\ mobile rotary irrigator of Australian design is now being manufactured in Ashburton.

It is called the Briggs Roto Rainer. A new company, Briggs Irrigation, Ltd, holds the New Zealand patents for it. Mr Les Briggs. a director of the company, says that the reason they have brought the machine into New Zealand is that as a low pressure unit it is economical in the use of energy and has a low running cost. Because it worked on low pressure the underground mains could be cheaper, less powerful pumps were required and running costs were lower. The operating cost, he said, would be about equivalent to that of hand moved units. While the capital cost of an irrigation scheme was important, it was not as important as the running cost for the next 20 years. At present the Briggs are manufacturing an irrigator of only one size, though Mr Briggs says that he can see that in the future there could be a place for similar units of varying sizes. The standard unit now being turned out is about 69 metres (225 ft from tip to tip, but because the boom tops any fence it can readily be shifted between paddocks and there is no need for farmers to make alterations to their fence lines or cut down trees in plantations or shelter belts.

Its movement or travel is achieved by the rotation of the boom. On one side of the central turntable or chassis the boom has five nozzles while on the other side there is only one nozzle at the extreme end of the boom. This means that more water is being released on one side than the other and this causes an imbalance of torque which causes the boom to rotate. This rotation, by means of cams on a turntable, operates a mechanical lever and winch mech-

anism which results in the irrigator winching itself across a paddock to an anchor point. The watering width can vary from about 92 metres (300 ft to 114 metres (370 ft and the ground speed from 15 centimetres (6in) to almost a metre (3ft) per minute. The variation in travelling speed is obtained by altering the angle of the end jets and speeding up the rotation of the boom, or by removing cams from the turntable.

The irrigator is supplied with a 203 metre (10 chain) 11 centimetre (4|in) rubber hose and using a sub main line the machine can travel up to 508 metres (25 chains) in one setting and cover an area of between 4 ha (10 acres) and 5.6 ha (14 acres). A feature of the machine is that it can be set to do all of a farmer’s irrigating in a working day and the 508 metre run just referred to could be done in 22 hours applying the equivalent of five centimetres (2in) of water. On a 406 metre (20 chain) run at the same speed it would apply six centimetres (2Ain). The application rate can, in fact, vary from 2.5 centimetres (lin) to 12.5 centimetres (sin).

The water required to run the machine ranges from 94,500 litres (21,000 gallons) to 121,500 litres (27,000 gallons) and it has to be fed to the machine through a 12.5 centimetre or sin pipe.

As already mentioned, a feature of the machine is that it works at very lowpressure — 240 to 400 kilopascals, or in terms that are more recognisable about 401 b to the square inch. This means that it requires a lower horsepower pump to operate the irrigator. Thus where the water is being taken from a surface supply the pump would need to be from about 35 to 60 horse-

power, but where the supply is being drawn from a deep well the horsepower requirement would vary according to the depth of the well and the head required.

The machine is versatile, in that in spite of its size it can be readily shifted both within a paddock and from paddock to paddock. It will go through a 4.3 metre (14ft) gateway and will operate in a square or rectangular paddock and also over a fence because of the height of the boom. At the centre the boom is 2.5 metres (Bft) off the ground and is adjustable so that it can be up to 4.6 metres (15ft) off the ground at its ends. Thus there is no need for a farmer to alter his fences or interfere with his shelter belts.

Shifting is also only a one-man operation and it is estimated that it would take between 30 minutes and an hour to shift and reset the machine.

It does not need to rely on clean water as the smallest nozzle is of 1| centimetres or Jin diameter and can readil- handle any grit. The nozzle sizes range up to slightly more than three centimetres (1 l/3in), with the smallest nozzles being on the inner side of the boom and the larger ones towards the end. The sort of nozzles used will naturally vary with the sort of cover or crop being watered. Mr Briggs says that wind distortion is less than with most other irrigators because a lot of the water is carried in the boom almost to the extremity of the watering circle.

The design of the boom is something that Mr Briggs thinks will contribute to its length of life. It virtually floats and is

tensioned and stayed with wire ropes. This means that there is no problem in a wind. There is no stressing. In a recent south westerly gale it turned automatically into the wind and sat into the storm.

Mr Briggs also notes that there are no fast working parts about it to quickly wear out.

In Australia where the boom and turntable have been in use for 13 years and the irrigator has now had two seasons as a mobile machine it has been built by Upton Engineering at Corowa in New South Wales.

Now holding the New Zealand patents for the irrigator, Briggs Irrigation, Ltd, have started manufacturing the machine at Ashburton. Up till yesterday morning Mr Briggs said that 10 had been ordered.

The cost, including the hose and a hose reel and purging unit is $21,500, which Mr Briggs says is reasonable in the light of its capacity. On their property at BankSwe Briggs Brothers are planning to use three of the machines on 480 hectares (1200 acres) that they have already piped or are in the process of piping. Under most weather conditions it is expected that they will be able to apply five centimetres (2in) to 6.25 centimetres (2Jin) of water to the whole area in about 32 days. The task is likely to occupy about half of'one man’s time.