n. 1/2022 21 PLOUGHS FOCUS ruote che avanzano sul piano di campagna. Le due soluzioni presentano entrambe diversi vantaggi e svantaggi; in estrema sintesi, con le ruote nel solco l’aratro lavora maggiormente in linea con il trattore, ma gli pneumatici di un lato della macchina hanno un’aderenza ben diversa da quelli dell’altro lato, sia per la differenza di peso del mezzo che grava su di essi (dovuta all’inclinazione del trattore), sia per l’aggrappamento che non è uguale, dato che una coppia di ruote esercita la trazione sul fondo del solco (= terreno nudo), mentre l’altra lavora su una superficie tipicamente inerbita e/o con residui della coltura precedente. Questi problemi sono risolti con l’aratura fuori solco, ma in questo caso il tiro del trattore non è in linea con la direttrice dell’aratro, generando quindi significativi sforzi laterali. Fino a qualche tempo fa, per l’uno o l’altra delle soluzioni dovevano essere adottati aratri specifici; ora invece, grazie alle more in line with the tractor, but the tires on one side of the machine have a quite different grip from those on the other side. This is due both to the difference in weight of the vehicle that rests on them (due to the inclination of the tractor) and to the fact that the grip is not the same since one pair of wheels exerts traction on the bottom of the furrow (= bare ground), while the other works on a surface that is typically covered with grass and/or residues of the previous crop. These problems are solved by ploughing outside the furrow, but in this case, the tractor's pull is not in line with the direction of the plough, thus resulting in lateral forces. Until recently, specific ploughs had to be adopted for one or the other solutions. Now, however, thanks to their extensive adjustment possibilities, models are available that can operate in both modes. Wide headstock To maximize traction, modern tractors are equipped with increasingly wide tires, with cross-sections as large as 700 or 800 mm for higher horsepower models. In furrow ploughing, this leads to no minor compaction of the soil ploughed in the adjacent pass with subsequent transit. To overcome this problem, many manufacturers offer significantly wider than standard mouldboards, which can leave a broader bottom of the furrow and laterally move away a greater quantity of soil, thus creating a smaller overburden. Safety In addition to the three basic fractions (i.e., sand, silt, and clay), the skeleton, i.e., gravel, stones, and rocks, must always be considered in primary tillage. The latter, and in particular those that are completely buried, can cause significant problems when ploughing, causing even serious breakages. For this reason, in such conditions, ploughs have long been equipped with safety devices: the simplest and most economical is the shear bolt, which, if stressed (by shear or sometimes by traction) beyond the breaking point, disconnects the body involved in the impact with the stone, avoiding damage. Sui modelli maggiormente accessoriati, le varie regolazioni dell’aratro sono gestite idraulicamente The plough's various adjustments are hydraulically controlled on the most accessorized models La larghezza di lavoro globale dell’aratro può essere variata idraulicamente anche in movimento, durante le normale operatività The overall working width of the plough can be hydraulically adjusted even while moving during routine operations
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