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.
Reversing mechanisms
At the end of each pass, the plough is rotated on me to bring the opposite set of bodies into The turnover mechanism is operated by a r. the plough headstock which is supplied with oil from the auxiliary services of the tractor hydraulic system. The ram, normally double acting, is controlled by a lever or a switch in the tractor cab. Some turnover control units have an automatic changeover valve which turns the plough in opposite directions each time it is used.
A manual turnover mechanism is used on many elderly reversible ploughs. The weight of the implement pushing forward towards the headstock when the plough is raised from work is used to reverse the bodies. The reversing mechanism is actuated with a hand lever and it has to be re-loaded by lowering the plough and pulling forward before it can be used again.