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Types of plough



Conventional right-handed ploughs and revers­ible ploughs may be mounted or semi-mounted and have a number of mouldboards which cut and turn furrow slices. Three-, four- and five-furrow ploughs are the most popular, but models with up to 14 furrows are made. Although the front of a semi-mounted plough is attached to the tractor hydraulic linkage it is never lifted completely clear of the ground. Most semi-mounted ploughs have either one or two castor wheels at the rear and on some models these wheels have a steering mechanism connected to the tractor linkage. Multi-furrow semi-mounted ploughs are raised and lowered in two stages. The front part is raised on the lift arms on reach­ing the headland and the rear is lifted after a slight delay by a hydraulic ram on the rear depth wheels. The front of the plough is lowered before the rear end at the start of the next pass to keep the ends of the furrows reasonably even in preparation for ploughing the headland.

Figure 1. This ten-furrow semi-mounted reversible plough can be used with the furrow-side tractor wheels running on the land or in the furrow.

 

A few trailed ploughs are still used with crawler tractors in some areas but this type of plough is more often seen at ploughing matches. The quality of work at these events is of a high standard but, as desirable as this may be, the low work rate achieved with these ploughs can­not be justified in modern day farming. How­ever, much can be learned at a ploughing match about the skills involved in good ploughing.

Articulated ploughs.Another type of multi-furrow semi-mounted plough, usually with 8 to 14 furrows, has a second pair of wheels about two-thirds of the way along the beam. These wheels, on a heavy axle, are self-steering and improve manoeuvra­bility when turning on the headland. The rear section articulates vertically from pivot points on the wheel axle to allow the bodies to folio. the ground contour and keep all of the furrow-at the same depth. When entering work the front bodies are lowered before the rear bodies ­on long semi-mounted and articulated plough-Some ploughs are controlled manually, other-have a sequential electronic control system. A typical system steers the plough on headland.-lifts the front bodies, followed by the rear bodies, operates the turnover mechanism and re-sets the plough behind the tractor. After turning, the front of the plough is lowered first. On some articulated ploughs the bodies are raiser and lowered in three stages - front, middle and rear.

 

Figure 2. Articulated reversible plough with the wheels on one side of the tractor running in the furrow.

Shallow reversible ploughs.Ploughing at a depth of 200 to 300 mm (8 to 12 in) is standard practice on most farms. Such depths are desirable for sugar beet and other root crops, but this is not necessarily the case for cereal growing. Not often used, they turn furrows from 60 to 180 mm (21/2 to 71/2 in) deer and 300 to 375 mm (12 to 15 in) wide. They have specially shaped mouldboards which completely invert the soil. Some have trash knives that deposit plant residues in the furrow bottoms. Man arable farmers now use minimal tillage implements for cereal crops.

Conventional ploughs.These plough have right-handed mouldboards and may be mounted or semi-mounted with one to eight furrows. These ploughs are still used in some parts of Great Britain and in many other countries. Most plough manufacturers still offer a range of right-handed ploughs which are lighter and less costly than reversible ploughs.

Figure 3. Shallow ploughs with up to eight furrows working at a depth of 100 to 180 mm and at speeds of 10-15 km/h (6-9 mph) can plough up to 4 ha in an hour.

 

Figure 4. A mounted conventional right-handed plough.

Disc ploughs.An alternative to the moldboard plow is the disk plow is used for primary tillage operation (Fig. 5.). These plows do not need an overload protection as the disks can roll over obstacles. As the disks have no landside or slip heel, all vertical and horizontal forces perpendicular to the direction of travel must be taken up by the tractor or by guiding wheels.

Rarely seen in Great Britain, these ploughs have large rotating discs instead of mouldboards. The disc cut and turn furrow slices but do not bury the surface trash. Disc ploughs are common in countries where this does not matter as the trash is soon scorched by the sun. Both right-handed and reversible disc ploughs are made.

The quality of inverting and crumbling the soil is lower than with the moldboard plow, and great amounts of organic residue can be a problem. Working at shallow depths over a longer period can result in heavy plow pans. Finally, due to the shape of the soil-engaging implement, the bottom of the furrow is not level. Nonetheless, due to its simplicity and robustness, the disk plow plays a major role in areas with difficult soil conditions where only limited amounts of drawbar power are available.

Figure 5. Disc plow.

 

Disks used for plowing and harrowing are made out of a portion of a sphere, thus creating the disk shape. Their common dimensions are 410–1270 mm in diameter and a thickness of 4.5–9 mm and a curvature of about 2.5 times the diameter for the plow and 1.2 times the diameter for harrows (Fig.6.). The disk will wear externally, showing a parabolic profile with external bevel. To facilitate the penetration into hard soil, the disk could be made with indentation. However, moist residues can limit the penetration.

Disks can be used for disk harrows or disk plows. For harrow disks, the tilt angle is zero. The disk angle can be adjusted from 15 to 25 (Fig.6.). In the case of a disk plow, the tilt angle can be adjustable from 10 to 25, the disk angle can be either fixed or adjustable (40 to 50).

Figure 6. Dimensions and working angles at disks for tillage.

 

The disk action on the soil is somewhat similar to that of the cylindrical moldboard type. The double obliquity placement of the disk causes its rotation once it is moved forward. This movement facilitates the cutting of the soil and its lateral displacement as a result of soil-metal friction and the soil aggregate acceleration. The working depth depends on both disk angle and the weight per body. There are two types of harrow disk: medium harrows with less than 80 kg/disk and heavy ones having more than 120 kg/disk.

 

Figure 7. This semi-mounted reversible plough has variable furrow width adjustment

and rear-wheel steering.

 

2. Reversible ploughs

These ploughs date back to the days of the steam engine and the horse. In almost universal use on British farms, they have right- and left-handed mouldboards enabling them to work up and down the same furrow. Reversible ploughs may either be mounted or semi-mounted and are heavier and more expensive than right-handed models, but they have the great advan­tage of leaving a level surface which makes seedbed preparation and harvesting easier. Very little marking out is necessary before ploughing can start and idle running on the headland is minimal compared with conventional ploughs.

Driving the tractor with the furrow-side wheels in the furrow bottom provides the most efficient line of draft between tractor and plough. It is also easier to steer the tractor and driving with the front wheel against the furrow wall will keep the front furrow at the correct width. This is less satisfactory when using a tractor with very wide front tyres, for although they make better use of the tractor power, the tyres may compact part of the last furrow slice turned on the previous run. The use of furrow widener (Plate 8.) or a longer mouldboard on the rear body will overcome the problem. The latter moves the soil further towards the ploughed land leaving more room for the tractor wheels on the next run.

Plate 8. The furrow widener on this plough body allows wide tractor tyres to run in the furrow bottom without compacting the soil ploughed on the previous pass.

 

Driving with all four wheels on unploughed land is another solution to the problem of wide tyres. Semi-mounted ploughs can be hitched inare heavier and more expensive than right-handed models, but they have the great advan­tage of leaving a level surface which makes seedbed preparation and harvesting easier. Very little marking out is necessary before ploughing can start and idle running on the headland is minimal compared with conventional ploughs.

Figure 9. The parts of a reversible plough.

 

Driving the tractor with the furrow-side wheels in the furrow bottom provides the most efficient line of draft between tractor and plough. It is also easier to steer the tractor and driving with the front wheel against the furrow wall will keep the front furrow at the correct width. This is less satisfactory when using a tractor with very wide front tyres, for although they make better use of the tractor power, the tyres may compact part of the last furrow slice turned on the previous run. The use of furrow widener (Plate 8.) or a longer mouldboard on the rear body will overcome the problem. The latter moves the soil further towards the ploughed land leaving more room for the tractor wheels on the next run.

Driving with all four wheels on unploughed land is another solution to the problem of wide tyres. Semi-mounted ploughs can be hitched in a way that allows the tractor to run on unbroken land and pull the plough in correct alignment without any sideways movement (crabbing).

Plate 10. A 12-furrow articulated plough with the tractor running on the land. This outfit covers many acres in a day but the furrow wall is rather ragged. This is due to the lack of disc coulters on the rear bodies and the fact that the driver does not have the advantage of steering the tractor against the furrow wall.

 

Plate 11. Hydraulic turnover mechanism on a mounted reversible plough headstock.

 

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