n. 11/2023 45 TECHNOLOGY nificantly higher cost than rigid axles, its appearance in the tractor market initially concerned high-power machinery. Among other things, the independent-wheel solution has a significantly smaller footprint than the classic one: this allows the steering angle to remain very wide so as to improve maneuverability, especially for high-tonnage tractors. For example, John Deere and Fendt have been adopting this architecture on high-end models for some time now. In detail, the Fendt 1000 Vario is fitted with four-bar linkage suspension whose travel can be set manually, depending on the load, so that comfort and safety in driving the vehicle remain optimal at all times, up to the maximum construction speed of the machine. In the area of specialized tractors, a turning point was marked by the introduction on Same Deutz-Fahr's Frutteto model of the Active Drive system, i.e., automotive-derived independent four-bar linkage suspension with automatic electronic damping control, defined based on sensor signals that monitor tractor speed, steering angle, as well as forward speed and hydraulic cylinder position. This configuration also includes an anti-sagging effect on the front end when braking (anti-dive) and an anti-roll action (anti-roll), which is important, especially when negotiating high-speed curves, automatically adjusting the system's stiffness to optimize stability and grip. In both cases, better stability of the vehicle-equipment assembly is ensured, and ultimately, a higher driving safety. For farm trailers, undoubtedly, the most advanced technology suspension is air suspension, similar to what has been the case for trucks for a long time now. Furthermore, independent-wheel suspensions are again available. ADR of Uboldo (VA) manufactures axles for both these features: compared to mechanical and hydraulic suspensions, air suspensions allow the ride height of the trailer body to be adjusted with a self-leveling function, regardless of the load size. Moreover, braking dynamics can be compensated for, thus providing the best grip on the ground at all times. Still from ADR, Hydro Evo, on the other hand, features a modular hydraulic solution that enables correct wheel travel on the same axle, even for considerably uneven profiles. In this way, in "gyratory" driving, i.e., with a cross slope, there is the possibility of keeping the flatbed horizontal, which benefits the vehicle's stability and, thus, driving safety. Steered axles No longer just two steered wheels (hence only one axle), but more than two, and sometimes all of them. This is a new frontier, both for tractors and equipment, which makes it possible to improve the The axles of wheeled agricultural machinery If tyres are the "shoes," axles can be considered the "legs" of the tractor and other wheeled agricultural machinery. Technical progress has led to the implementation of axles with state-of-theart performance steering and suspension systems, all to the benefit of vehicle handling and driver’s comfort. And axles equipped with full-electric drive have already appeared on the horizon tazioni dovute agli importanti carichi sopportati e alle inevitabili irregolarità della superficie del suolo agricolo. Non sorprende quindi che si sia affermato sul mercato un valido gruppo di costruttori specializzati, che producono in esclusiva (o quasi) assali per macchine agricole motrici e operatrici. Assali con sospensioni Da ormai diversi decenni la sospensione dell’assale anteriore dei trattori agricoli è realtà. Si tratta di un componente che, installato inizialmente per contrastare il beccheggio del mezzo nella marcia ad alta velocità, si è via via evoluto per migliorare anche il comfort del conducente, in un “pacchetto” che comprende anche le sospensioni della cabina e del sedile. In questo caso, a partire da assali rigidi incernierati centralmente, l’evoluzione ha visto la comparsa di sospensioni a semiassi indipendenti, con schema a quadrilatero articolato. Trattandosi di un dispositivo dal costo significativamente superiore a quelli ad asse rigido, l’apparizione sul mercato trattoristico ha riguardato inizialmente le macchine di alta potenza. Tra l’altro, la soluzione a ruote indipendenti ha un ingombro decisamente inferiore rispetto a quella classica: in tal modo l’angolo di sterzata può rimanere molto ampio, in modo da miglioraDa qualche anno si stanno diffondendo sui trattori sospensioni dell’asse anteriore con schema a quadrilatero articolato Front axle suspensions with four-bar linkage layout have been spreading on tractors for a few years now
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