Reversible Plough

Overview

A plough inverts the topsoil: it cuts a slice 30–55 cm wide and 15–30 cm deep, lifts it and turns it roughly 135° into the previous furrow, burying weeds, crop residue and manure and exposing fresh soil. A conventional plough turns soil only to the right, which forces ploughing in "lands" and leaves ridges and dead furrows across the field. The reversible plough removes that constraint by carrying two mirrored sets of bodies, five right-handed and five left-handed on a typical machine, on a frame that rotates 180° at each headland. The operator works back and forth along the same line, every furrow thrown the same direction, and the finished field is flat.

Each furrow is cut by one body, a cluster of bolt-on parts on a Frog: the Share makes the horizontal cut, the Mouldboard lifts, shatters and inverts the slice, and the Landside presses against the furrow wall to react the large sideways force of turning soil. A Skimmer ahead of each body pares off the trash-laden surface layer and drops it in the furrow bottom so the main slice buries it completely, and a Disc Coulter before the rear body leaves a clean vertical wall for the next pass. Shares are the consumable: boron steel, reversible or replaceable, lasting from 20 ha in flinty soil to 80 ha in kind loam.

How it works

At the headland the operator lifts the plough on the linkage and pulls one spool. The Turnover Cylinder, acting on a crank around the Turnover Shaft, swings the entire 1.5–2 t frame over the top; a Sequence Valve reverses the cylinder porting automatically at half rotation, so the full 180° completes in about eight seconds without the driver touching a second control. Adjustable Rotation Stops define the working tilt on each side, and the tapered-roller Swivel Bearing Set in the Headstock Body carries the whole plough weight in bending during the throw. The rear gauge wheel flips with it: its Wheel Arm swings to the new working side, cushioned by the Wheel Damper.

In work, geometry settings determine both job quality and fuel burn. The Depth Spindle on the wheel sets maximum depth while the tractor's draft control floats the linkage; the Front Furrow Adjuster matches the first furrow to the tractor wheel track; and the Pitch Screw sets share pitch so the plough pulls itself into the ground without dragging on the points. On vari-width models a Vari-Width Cylinder working through the parallelogram Width Linkage rotates all five Plough Legs by the same angle, changing every furrow from about 30 to 55 cm simultaneously from the cab, narrow for full inversion of grassland, wide for fast stubble work.

Draft force runs 5–7 kN per furrow in medium soil at 25 cm depth, so a five-furrow machine needs a 130–200 hp tractor and covers 1.2–2.0 ha/h at 7–9 km/h. Body shape sets the speed window: long, gently twisted boards turn unbroken furrows at low speed, while modern universal boards shatter and turn properly at 8 km/h.

Overload protection

A plough body striking a buried stone at 8 km/h sees loads that would bend the Main Beam if nothing gave way. Two systems are common. Shear-bolt protection puts a calibrated Shear Bolt in each Leg Clamp; the bolt fails, the leg swings back on its Leg Pivot Pin, and the driver fits a new bolt in minutes. Auto-reset protection replaces the bolt with a Auto-Reset Leaf Spring spring pack holding roughly 600 kg at the share point: the body rides up over the obstacle and snaps back into work without stopping, standard in stony regions, at a weight and price premium.

Context

The reversible mouldboard plough remains the reference tool for full soil inversion: nothing buries weed seed, slug pressure and disease inoculum as completely, which is why it has regained ground where herbicide-resistant blackgrass defeats min-till systems. Its costs are equally well known, at around 20 litres of diesel per hectare it is the most energy-intensive field operation, and the smeared pan a worn share can leave is the textbook argument for the subsoiler. Most arable farms now hold both ploughs and non-inversion tools and choose per field per season.