2.1. Rear Delivery Spreaders

The heavy duty steel floor has an endless chain and slat conveyor which moves the manure to the rear of the spreader. Here, high speed shred­ders or beaters tease out and spread the manure to a width of 6-14 m (20-45 ft). Some high-capacity machines have spreading widths of up to 24 m.

Various types of spreading mechanism are used. Some machines have a single horizontal rotor, which may be a spiked rotor or an auger with left- and right-hand flights to shred and spread the manure. Other models have two or three horizontal rotors for this purpose.

Another design has vertical spreading rotors - two, three or four in number - spaced across the back of the machine. The moving floor conveyor and spreading mechanisms may be driven by the power take-off, protected with an overload slip clutch or by a variable speed hydraulic motor supplied with oil from the tractor hydraulic system.

Figure 12.2 Four vertical rotors shred and spread manure carried to them by a twin chain and slat floor conveyor.

Figure 12.3 Rear view of a horizontal beater manure spreader

Rear delivery spreaders are best suited to manure with a high straw content, but some models can be adapted for use with slurry and chicken litter. A rear gate or slurry door, raised and lowered by hydraulic rams, restricts the flow of semi-liquids to the spreading rotors. A special chicken litter attachment can be used on some models of manure spreader with a hor­izontal spreading rotor. It consists of a row of spinning discs, usually four in number, under a large metal cover. The rotor feeds the litter at a controlled rate to the hydraulic motor driven discs which spread it over a wide area.

Capacities usually range from 5 to 24 tonnes of farmyard manure. Some spreaders have a load cell under the body which measures the weight of the load. Application rates will vary from about 1 tonne up to 50 tonnes per hectare (20 tons/acre).

When loading a rear delivery manure spreader, fill the front first and it will be easier to manoeuvre the tractor and loader if the spreader is set at an angle of about 30 degrees to the heap.

Drive engagement The power take-off lever on the tractor engages drive to the floor conveyor and shredding mechanism on power driven models and the auxiliary services valve controls oil flow to the hydraulic motor.

Application rate is altered by changing the speed of the moving floor conveyor with a lever or screw adjuster on power take-off driven models or by varying oil flow on spreaders with a variable speed hydraulic motor. Tractor forward speed, altered with the gearbox, also changes the application rate. A low forward speed and high floor conveyor speed gives a high application rate.

Figure 12.4 A rear beater farmyard manure spreader equipped with doors and a spinning disc for spreading slurry.

2.2. Rotary Spreaders.

The open sided cylinder shaped trailer body or drum of a rotary sidespreader makes it ideal for handling very wet materials as well as farmyard manure. A number of high speed flails attached to a centrally mounted rotor by heavy chains throw the manure from the side of the spreader onto the ground. The rotor shaft is driven by a chain and sprocket reduction unit from the power take-off. Rotor speed is varied by fitting different size sprockets to the chain drive, which is protected by an overload safety clutch.

When starting to spread with a full load only the outer flails distribute the manure. Before the spreader is filled the flails should be wrapped around the rotor. When spreading commences with a full load, the flails at each end of the rotor distribute the manure and as the load is dis­charged more of the flails are able to swing free and gradually empty the spreader from both ends towards the centre. A hinged lid above the drum, operated with a hand lever or a hydraulic ram, is opened to facilitate filling.

Plate 12.5 The arrangement of the flails on a rotary manure spreader.

Figure 12.1 Sectional diagram of a rotary manure spreader.

Rotary manure spreaders are made in various sizes with capacities from 3-12 tonnes or approximately 1,200-4,800 litres and a spread­ing width of 3-12 m depending on the size of the machine. Application rates are within a range of 12-60 tonnes per hectare (5-25 tons per acre) depending on model, but this can be increased with a second dressing.

Drive engagement. The tractor power take-off lever engages drive to the flail rotor.

Application rate Tractor forward speed, changed with the gearbox, varies the quantity of manure spread per hectare. When selection of different forward speeds fails to give the required dressing, the flail speed can be changed by fitting different sized sprockets on the chain drive to the rotor shaft. Flail rotor speeds vary between 200 and 350 rpm depend­ing on model.