LOW-VOLUME SPRAYERS: Construction and Operation

New Zealand Journal of Agriculture, Volume 83, Issue 4, 15 October 1951, Page 289

LOW-VOLUME SPRAYERS: Construction and Operation

| OW-VOLUME spraying with hormone weedicides has made possible a new era in weed control in pastures, crops, and waste spaces in New Zealand. The principle and components of a low-volume sprayer were explained in last month's "Journal" in the first section of this article by C. J. Crosbie, Machinery Instructor, Department of Agriculture, Christchurch. For the benefit of the mechanically minded farmer this section describes not only the operation of the equipment but the building of such a machine—a feat that is well within the ability of the average farmer with a small workshop and who can call on the services of a welder where necessary. A low-volume sprayer is built from units readily available and uses standard pipe fittings and hose with which a farmer who has built his own water-supply system will already be familiar.

least four makes of low-volume sprayer can be bought in New Zealand, but a farmer with a mechanical turn of mind may obtain great satisfaction from building his own machine. A simple efficient machine spraying 12ft to be mounted on a tractor can be built for about £22 as follows (prices at Christchurch in May, 1951)-

The construction of such a machine is well within the ability of any man experienced in handling piping and pipe fittings, and home construction offers scope for including any special features not found on commercial machines. Mounting the Sprayer When the type of sprayer to be built has been decided the next decision to be taken is what vehicle to mount it on and how to mount it. The choice is wide and will vary with the circumstances. Such a machine is usually mounted on the farm tractor, which can travel at low speeds and has a self : governed engine to maintain a steady speed. However, it may be mounted on a farm trailer drawn behind a tractor (especially useful where water is scarce and must be hauled long distances, for several 44-gallon drums of water can be carried) with a small petrol engine to drive the pump, or it can be mounted on the farm truck. For country so steep or rocky that vehicles cannot traverse it the sprayer may be fitted on a pack saddle on a sturdy horse and the boom carried by two operators. However as the sprayer is usually mounted on a tractor, that method of construction will be considered in this article., Details of Construction A sprayer that is easily fitted and quickly removed allows the tractor to be released for other duties. It may be built on the sides and front of the tractor with the pump driven from the belt pulley, leaving the drawbar and power take-off free; shutting off the control valve to the boom and folding the boom in make the tractor ready for other work at a moment’s notice. Alternatively, the “easy-on

easy-off” type shown in the diagram on the left, and perhaps the easiest to build, is fitted on with four bolts and one hose clip, so that the whole unit can be released in a few minutes, set on blocks, and put back on the tractor in the same time. The sprayer stays as one unit, so no parts become mislaid or lost and assembly is greatly facilitated. This neat type of sprayer will be considered further, as many of the details are applicable to other types. The “easy-on, easy-off” type of sprayer is fitted on a platform built over the tractor drawbar and supported by two angle-iron members bent and bolted to the drawbar and to the back axle with four bolts. The gear pump is bolted firmly to a block of wood or an iron strap so that the centre line of the pump shaft lines up with the centre line of the power take-off shaft. The supplier of the pump or the local engineering shop

will supply a sleeve (equal in diameter to the power take-off shaft), which is secured to the pump shaft with a grub screw. The union between the pump and the power take-off shaft is made with a 6in. length of ordinary hose, l|in. in diameter for a Ifin. shaft and lin. in diameter for a ljin. shaft. Two hose clips secure the hose in place and only one need be undone to release the pump when the sprayer is to be taken off the tractor. The strength of ordinary hose is ample to transmit the i horsepower required to drive the pump, and should it perish after a few years, it costs only about a shilling to replace. A belt drive using an Asection V belt can be arranged with V-belt pulleys, but is more costly. A chain drive is very expensive and not necessary to transmit the small amount of power required. The filter can be attached directly to the pump and a suction hose run to the spray tank, which' is usually a 44-gallon drum. The suction hose may be dropped down the large bung of the drum or may be fitted to a short length of pipe screwed into a pocket bronzed on to the bottom of the drum, which is preferable, as it facilitates draining the drum after washing down. Caution is needed when welding old petrol or oil drums because of the very real danger of the torch flame igniting the fumes and causing an explosion. The fumes may be removed by passing live steam through the drum for several hours, or the drum may be filled with carbon dioxide gas by putting battery acid or baking soda in it or emptying a fire extinguisher into it. Alternatively, the drum should be nearly filled with water and arranged so that the air space left is in contact with the open air and adjacent to the part to be welded. Too much caution cannot be exercised, for petrol drums that have held water for months have been known to explode under a welding torch because of the presence of petrol held in the end seams. The delivery line from the pump is built up as shown in the diagram on the first page, a relief valve being included if the pump has not one built in. The pressure gauge must be placed where it can be seen readily, and if an acid solution is to be used in the sprayer, the gauge must be fitted on top of a short length of pipe so that an air cushion exists between the spray material and the gauge; if the gauge is set directly on a spray line carrying acid, its delicate mechanism is soon destroyed.

The control valve—a quick-acting valve, a gate valve, or most usually a stop-cockeither has a remote-control lever or is fitted on to the tractor mudguard within easy reach of the operator, hose being used to carry spray material to and from it. The boom can be fitted in front of the tractor, under it on a row-crop model, or behind it; in whichever place it is mounted, the operator will not be able to see at least two of the nozzles because of the tractor engine or the spray tank. Perhaps behind the tractor is the easiest place in which to fit the boom, for welding a vertical length of light angle iron to each rear corner of the platform allows it to be easily mounted as part of the sprayer and removed with . the sprayer as -a complete unit. _ . . _ Design of Boom Th A lAnp+h nf hnnm +« Ko „ m denend on two fact^r«— If epe d on two factors the width of

the gateways on the farm and the area to be sprayed. The usual farm gate is 12ft. wide, and a straight boom spraying 12ft. wide is built up from a length of pipe about 10ft. lOin. long and projects about 2in. past the outer nozzles, so it can pass through the gate with ease. For road travel the boom can be carried along the side of the tractor in special clips arranged for it. Wider booms are usually hinged in three sections to swing back or up for road transport and passing through gates. A folding boom is also a safeguard against damage caused by an impact such as that of striking a fence post when opening up a field. A boom up to 18 or 20ft. wide with the outer ends stayed to a central post or posts can be supported on the average tractor and worked with ease on cultivated ground. A boom about 30ft. wide needs light castor wheels on the outer ends to keep it parallel with the ground. Shorter booms supported from the tractor are used for spraying rough ground to avoid boom whip caused by the tractor rolling, but an exceptionally short boom causes waste of time except in very special circumstances. Three times round a field with an Bft. boom has only the same result as twice round with a 12ft. boom. Usually 9 to 10ft. booms are used on cow pastures and 12 to 15ft. booms on cultivated land. An 18ft. boom covers two 15-coulter drill widths, so if the sprayer operator drives up the centre drill-wheel mark, the machine sprays two drill widths without risk of missing or overlapping. The area covered by these wide booms can be calculated easily as detailed in the section on calibration which follows. Straight booms 10 to 12ft. long need to be made from lin. galvanised-iron pipe or steam pipe and larger booms

from ljin. pipe. Folding booms, made up of shorter sections, can be made from jin. piping, and for an outer boom carrying only two or three nozzles gin. piping is sufficient. The boom should be adjustable for height so that the spray fans meet just above the tops of the herbage. Provision for this can be made with a system of levers, ropes, and pulleys or of levers and bell-cranks; the easiest method is to drill the two vertical angle-iron supporting posts at 2in. centres and clamp the boom to them with a simple bracket or U bolt. Two types of hinges for folding booms are shown in the diagrams on this page, the spray material in each case being taken past the hinge in a short length of hose. The nozzles are usually screwed into Jin. brass sockets bronzed to the underside of the boom, but two other methods, the inverted U tube and the side arm, are also illustrated below. If difficulty is met in bronzing the brass sockets to the boom because of the low melting point of the brass, “Silphos” rod may be used, as it has a very low melting point. Drilling and tapping the boom and screwing the nozzles directly into it is not

recommended, because at the most only one complete turn of thread holds the nozzle in position, making a joint that is very weak and subject to leakage even at the low pressures used. Calibration With the sprayer built, the next step is to calibrate it; that is, to determine the exact quantity the machine is spraying per acre at a specific pressure and throttle setting. The only information needed is the delivery of the boom in an hour and the area covered in an hour, so only two items need be measured — delivery rate of a nozzle (or better still the average of several) and the speed of the tractor at a particular throttle setting in a particular gear. Boom output: With the engine turning at a speed equivalent to a tractor speed of 3 to 4 m.p.h. in third gear, and the relief valve set so that liquid is delivered to the boom at 301 b. per square inch (the usual operating pressure of a low-volume sprayer), the delivery rate of a nozzle (or the average of several) is determined by noting the time it takes to fill a vessel of known capacity. For example, with “Monarch” 32 nozzles fitted 18in. apart on a 12ft. boom and operating at a pressure of 301 b. per square inch, a quart measuring jug is filled by each nozzle in an average of 2 minutes 31J seconds, which represents a rate of 5.94 gallons per hour. Multiplying this by the number of nozzles on the boom (eight) gives 47.5 gallons per hour, which is the output of the boom. Speed: The tractor is usually operated in third gear at about threequarter throttle to give a forward speed of between 3 and 4 m.p.h. This speed is checked against the time taken to travel a known distance say, a 12-chain fenceline or past four power poles on the roadside (usually 3 chains apart). If this distance is covered in 2 minutes 34 seconds, the speed of the tractor is 3.5 m.p.h. The throttle setting which gave this speed is marked so that it can be readily set again and the gear noted; it may be either second or third according to the make and model of tractor. Area covered: A boom Ift. wide covers 0.121 acre in travelling 1 mile. Therefore a 12ft. boom on a tractor travelling at 3.5 m.p.h. will cover 0.121 X 12 X 3.5 = 5.082 — 5 acres per hour.

Spraying rate: The spraying rate per acre is obtained by dividing the boom output in an hour by the area covered in an hour. In the example, 47 J gallons divided by 5 acres equals 9.5 gallons per acre. Therefore, when this sprayer fitted with “Monarch” 32 nozzles 18in. apart on a 12ft. boom is operated at 301 b. per square inch and 3.5 m.p.h., it sprays 9.5 gallons per hour. Different batches of the samesized nozzles may vary a little from their rated capacities, and operators are advised to check the delivery of the nozzles supplied to them by the method described. Making the Mix If it is desired to apply weedicide to an area at the rate of lib. of 2, 4-D acid equivalent per acre with a sprayer which delivers 9.5 gallons per hour, each lib. of 2, 4-D acid equivalent must be mixed with water to make a total mix of 9| gallons. If the weedicide bought is a 10 per cent, concentration, lib. of 2, 4-D acid equivalent will be contained in 1 gallon of concentrate, so 1 gallon of concentrate plus 8 J gallons of water will make enough mix to treat 1 acre. If the concentrate is 40 per cent. 2, 4-D acid equivalent, 11b. is contained in i gallon, so 1 quart of the concentrate plus 9> gallons of water makes the mix. Multiples of these figures make mixes for larger areas. For good spraying results these calculations must be worked out accurately and the mix made with care. The recommended rate for treating a certain weed includes some margin to ensure that the weed is killed under a wide variety of conditions. The kill is much more sure if this allowance is

fully used up in overcoming variations of climate or soil conditions; that is, if the treatment is applied at exactly the recommended rate and nothing is wasted in covering up inaccuracies of application. When making up the mix in the tank it is a good idea to pour a few gallons of water into the tank first, add the concentrate, and then add the rest of the water. If the concentrate is poured in first, it flows down the outlet pipe to the pump and little mixing occurs when water is added. Operating the Sprayer If the pump is set going while the machine is travelling to the field to be sprayed, the spray material can be circulated from the tank, through the pump, past the relief valve, and back to the tank to make a good mix. Slackening off the relief valve, or opening the by-pass valve if the machine has a self-filling device, ensures that the pump is working at no head of pressure while this is going on. Before the control valve is opened to fill the boom the machine should be manoeuvred so that the boom is against a fenceline. Some spray must be passed through the boom before it is clear of air and all nozzles are spraying evenly, and this material is thus deposited under the fence where it may kill the herbage but will do little harm. In the field the sprayer may be driven round and round to finish in the centre or it may be worked back and forth to finish at the other side. Perhaps the first is better, because the wheel marks of the tractor in the previous path of the machine show up better and may be used as a guide for the next path. The use of a marker to make a line on which to drive for. the next path is not recommended, for it has been found that the marker must be so heavy to make a mark in pasture or

crop that it is difficult to mount on the tractor. Much better is to mount a light rod or pipe on the outer end of the boom and from it drag a short length of light chain which dangles on the nearer wheel mark of the previous path of the sprayer. Missing and overlapping are both avoided, ensuring a . good weed kill without damage to the crop through double spraying. When a field is sprayed round and round, small crescent-shaped areas are left unsprayed in each corner on each

round. Whether these corner misses should be cut out after the field is finished is problematical. In the interests of weed control they should be, but they provide control areas that show the degree of weed contamination had the field not been sprayed. A sprayer used for hormone weedicides that are esters (oil-based concentrates) of 2, 4-D cannot be washed completely free of weedicide before other sprays are used on plants susceptible to 2, 4-D, such as the brassicas and the crucifers. The esters of 2, 4-D are absorbed into either rubber or plastic hose and, though the surface layers can be washed off, more comes to the surface. Tomatoes can be killed with solutions of 2, 4-D of the order of a few parts per million. However, with care the -based solutions of the amine and sodium-salt formulations of 2, 4-D and the M.C.P. sodium-salt formulations can be washed out of the sprayer to leave it clean for other work. The machine should be washed well with clean water, rinsed with a warm solution of ammonia or caustic soda, rinsed with clean water, and then filled with clean water and allowed to stand overnight. Another rinsing with clean water in the morning should precede spraying with an insecticide or fungicide. Other Uses of a Sprayer If a low-volume sprayer can be used for other work outside the spraying season, return from the capital outlay is increased and a means provided of doing work previously done at greater cost in time , and labour. Out-of-season uses of the air-com-pressor type of sprayer are legion in the implement sheds and workshops of modern mechanised farms and will not be discussed, but the pump type of machine also has its out-of-season uses which are not widely known. Creosoting and Borer Proofing A low-volume sprayer can be J used for creosoting farm buildings for protection from wood rot and borer in

place of a brush or a knapsack sprayer. The suction hose of the sprayer is dipped into the drum of creosote and a hose from the relief valve returns the overflow to the drum. The unit is set to work at a pressure of 20 to 251 b. per square inch and the spray material is delivered through a length of jin. hose to a knapsack-sprayer hand lance fitted with a control valve and a fan-type low-volume nozzlea “Monarch” 28 or ' 32 or another of similar size. With the nozzle held about 3in. from a stud the spray will fan out to cover the 4in. face of the stud and, starting from the top, the nozzle is lowered just ahead of the run-off down the stud. Holding the nozzle further away gives a wider spray for treating larger areas such as walls or floors. This method of creosoting is much quicker and more convenient than brushing. If borer proofing and rot proofing are required in a place where the stain from creosote would be objectionable —say, on the frame of a house that is to be lined with plaster and wallpapereda 5 per cent, solution of pentachlorphenol can be used. If the concentrate is diluted in , lighting kerosene, the spray will not stain plaster or wallpaper. A 40-gallon mix made by adding 4 gallons of 50 per cent, pentachlorphenol to 36 gallons of lighting kerosene costs about £ll and is. sufficient to treat the frame and floors of the average-sized bungalow. Protection for the eyes, nose, and throat is . desirable when using this mix and essential when working under the floor. The skin, too, needs protection from the “degreasing” property of the kerosene, and lanoline should be applied to the hands at night to prevent eczema. Fire Fighting In Canterbury and other areas subject to fire risk in summer keeping the low-volume sprayer pump permanently mounted on the tractor is a wise precaution. A l|in. pump mounted on the side of the tractor and driven from the belt pulley to avoid interference

with operation of the power take-off, and supplying water through a jin. hose fitted with a fin. nozzle, will give a solid jet to a height of 15ft. and discharge about 270 gallons per hour at a pressure of only 101 b. per square inch.* Keeping a few drums of water on a stand at a central point on the farm greatly facilitates loading the trailer and reduces the time taken to reach the fire. Many rural fires can be controlled in the early stages with this small fire-fighting unit. In the Orchard An efficient sprayer for disease control on small trees or fruit canes can be built cheaply on the same lines and when fitted with the correct nozzles will make efficient use of modern sprays that are true solutions. Bordeaux sprays that contain free lime are abrasive and would wear out the gear pump, which would need replacement at intervals. Even so, this cheap, efficient sprayer will appeal to a man establishing an orchard with limited capital. Grass-grub and Porina Control D.D.T. and B.H.C. - (benzene hexachloride) have placed a weapon for the control of grass-grub and Oxycanus (porina) in the hands of the farmer. They are usually used as mixtures with superphosphate applied with a drill or topdresser, but either can be applied as a spray. Both wettable D.D.T. and B.H.C. mix readily with water and can be sprayed on with a low-volume sprayer, for the water is only a spreading agent. A shower of rain after spraying provides more water per acre than could be applied with a high-volume sprayer. However, the object in applying D.D.T. is to get it on to the ground, so the sprayer is best used on bare pastures and, preferably before a shower of rain to wash residue off the herbage.

Sheep should not graze the pasture after it is sprayed and before rain because they eat the insecticide clinging to the herbage and it is not washed into the ground where it is required. One to 21b. of D.D.T. or B.H.C. per acre is not poisonous to stock. Control of Blowfly Strike Farmers in areas where sheep are subject to blowfly strike would do well to consider spraying the sheep with a mixture of D.D.T. and 8.H.C., now available from stockists of sheep dips. The mixture both controls maggots and repels flies, preventing strike and giving protection for up to 6 weeks. A low-volume sprayer can supply the mixture to a length of hose and a hand boom fitted with a small nozzle that is very suitable for use in the sheepyards The unit shown in the illustration on this page is driven by a small petrol engine and operates at a pressure of 601 b. per square inch. Spray was applied on the shoulders, along the back, on the rump, and into the crutch with the hand lance, and 100 sheep per hour can be treated by one man filling and emptying his own pens. A low-volume sprayer offers a means of effective weed control, using only small quantities of water per acre, requiring little capital outlay, and saving much time and labour when compared with the high-volume system. It can be easily built by the average . farmer from parts readily available and with only a little assistance from the local engineering shop. A farm-built sprayer offers scope for ingenuity in design to suit the circumstances, and whether built or bought the machine has many uses on the farm apart from its main purpose of weed control.

Some types of sprays can be dangerous to operators

PROLONGED exposure to sprays • containing D.N.O.C. or D.N.S.B.P. (both yellow sprays) can cause poisoning. Though little danger exists for a farmer using these materials on one or two days a year, contract sprayer operators exposed to these sprays for longer periods are strongly recommended to take every precaution against contamination caused either by splashes on the skin or by breathing spray-laden air. D.N.O.C. and D.N.S.B.P. are absorbed through the skin, nose, and mouth and build up in the body until a lethal dose accumulates. No antidote to this form of poisoning is known, and after an attack the victim either dies or recovers. Medical science cannot help. Symptoms of poisoning are excessive sweating, thirst, prolonged headaches, loss of appetite, and lassitude. A sprayer operator who suffers from such symptoms is well advised to discontinue the use of these two substances. ■ The hormonetype weedicides 2, 4-D, M.C.P., and 2,4, 5-T are harmless to man, bird, and beast.

* “Power Farming in Australia and New Zealand’’, November, 1950, pages 65 and 66.

Jin. gear pump and sleeve £ 7 s. 0 d. o Filter (built up from pipe fittings) 13 o Pressure gauge, 0 to 1001b. per square inch, 3m. face ...... ’ 1 5 o Relief valve, totally enclosed, side outlet . 1 10 0 gin. stop-cock g o lift, of lin. pipe for boom 14 o 10ft. of fin. hose and hose clips 1 2 o 8 low-volume nozzles and ,8 fin. brass sockets 4 10 0 Jin. pipe fittings (estimate) 10 o 44-gallon drum 10 o Angle iron, bolts, timber, etc. (estimate) .. 10 o Welding and drilling (estimate) 3 0 0 £21 10 0