n. 3-4/2026 31 TECHNOLOGY nica anche se resta, per tutte e tre le soluzioni, la possibilità di correzione manuale rispetto all’equilibrio trovato dal computer. Scopriamo allora com’è possibile trasformare in camosci macchine pesanti decine di tonnellate. Livellamento variabile. Parlare di mietitrebbie livellanti dice tutto e niente. A seconda delle necessità, la correzione della pendenza può essere più o meno incisiva, parziale o totale. Talvolta, non coinvolge nemmeno l’assetto della macchina. Lavorare in pendenza causa diversi problemi. Il primo è legato alla deriva del prodotto verso valle, sia negli organi trebbianti, sia in quelli di pulizia: ne deriva una granella più sporca. Se l’inclinazione aumenta, si hanno difficoltà di raccolta – essenzialmente in discesa, poiché il prodotto tende a cadere dalla testata o dal canale elevatore – fino ad arrivare, quando la pendenza è elevata, a rischi di stabilità della mietitrebbia stessa, con potenziale pericolo per il conducente. Il primo livello di correzione riguarda soltanto gli organi crivellanti. Cassoni con movimento laterale oltre che longitudinale redistribuiscono il prodotto su tutta la superficie, evitando accumuli che impediscono la pulizia dai residui. In alcuni casi si è anche pensato di dotare le mietitrebbie di sistemi di inclinazione dei crivelli, che li riportassero in piano almeno su pendenze trasversali non eccessive. Una diversa regolazione dei ventilatori – elevata in salita, delicata in discesa – aiuta invece a ridurre i problemi sulla pendenza lonCombine harvesters: when working on sloping ground Self-leveling technology for combine harvesters is an Italian exclusive, developed 55 years ago by Laverda and now exported worldwide. Let’s compare the three solutions for extreme slopes available on our market erything has changed since 1971: stability is now controlled electronically, although all three solutions still allow for manual correction of the balance determined by the computer. Let’s explore, then, how machines weighing tens of tons can be transformed into mountain goats. Variable levelling. Talking about self-leveling combine harvesters says everything and nothing. Depending on the need, slope correction can be more or less aggressive, partial, or total. Sometimes, it doesn’t even involve the machine’s suspension. Working on slopes causes several problems. The first is related to the crop drifting downhill during threshing and cleaning mechanisms: this results in dirtier grain. If the slope increases, harvesting becomes difficult—especially on downhill sections, since the crop tends to fall from the header or the elevator chute—to the point where, on steep slopes, the combine’s stability is compromised, posing a potential danger to the operator. The first level of correction concerns only the sieving components. Hoppers with both lateral and longitudinal movement redistribute the crop across the entire surface, preventing accumulations that hinder residue removal. In some cases, combine harvesters have also been equipped with sieve tilting systems, which bring them back to level at least on moderate cross-slopes. A different fan adjustment—high on uphill slopes, gentle on downhill slopes—helps reduce problems on longitudinal slopes. The next step involves so-called semi-leveling: a system of cylinders that acts on the gearboxes, correcting lateral slopes, generally up to 18%. It is perfect for Central Europe, where slopes are gentle and large machines are needed, which are difficult to level beyond a certain limit. Thirty-eight, ten, and thirty (or thirty-five). These are the numbers for extreme leveling, beyond which, so far, no one has ever gone. Nor is there any need to, given that they allow for work on high-mountain slopes. To achieve these, significant structural modifications to the machine are required. First and foremost, the machine must be sufficiently lightweight so that the lift cylinder rods can support it. This conflicts with the now-constant need for machines with ever-higher power ratings, even in hilly or mountainous areas. And in fact, some manufacturers offer dual leveling - front and rear - on six-shaker combine harvesters, which are therefore quite heavy. They achieve this with the aforementioned partial front leveling, to which they add two hydraulic cylinders to raise the rear. Not to the extreme angles of pure selfleveling, but enough to work on fairly steep terrain. But let’s return to the heart of this analysis: the most radiCilindri per il livellamento posteriore. Fissano l’assale al telaio Rear leveling cylinders: secure the axle to the frame
RkJQdWJsaXNoZXIy NTY4ODI=