n. 3-4/2022 71 TECHNOLOGY Fullmaneuverability between rows In specialized crops, the need to work without operational limitations implies the availability of highly evolved tractors in terms of steering devices. An overview of the original and partly new solutions available on the market pecially to improve the passage between rows, especially as regards the exit and entry into the inter-row space. To this end, various technical solutions have been identified, some of which are quite different from each other and some of which are absolutely new in the tractor field, but all of which share the objective of reducing the minimum turning radius as much as possible. What follows is a brief overview of what the market currently offers, with particular reference to the most recently launched technologies. New Holland SuperSteer New Holland tractors equipped with SuperSteer have been on the market for a few years now. The front axle is placed in a particularly forward position with respect to the engine compartment. An extensive overall steering angle (up to 76°) can be achieved, thanks also to the relative rotational movement of the axle itself, in addition to the normal movement of the wheels. Besides reduced turning radius, this obviously also entails an increase in the machine's wheelbase, so that - according to the manufacturer - with SuperSteer, front-mounted implements return more quickly to their working configuration after steering. In addition, the weight on the axles is better distributed with an increase on the front axle so that the amount of front ballasting can be reduced when working with heavy rear implements. Kubota bi-speed Again to reduce the turning radius on its 4-wheel drive models, the Japanese company Kubota has adopted the solution of increasing the rotation speed of the front wheels. Basically, employing a "hi-lo" gearbox and dedicated oil-bath multidisc clutches, when the steering angle of the inner wheel exceeds 30°, the peripheral speed automatically increases by 1.7-1.9 times (depending on the model). This enables the machine to "close" the curve sooner, with obvious advantages for headland turns and repeated turning operations in tight spaces. This results in a reduction in working time as well as in fuel and stress for the driver, who is spared repeated (and tedious) operations. In the long run, the wear factor is not to be neglected either, as in this case, it has less impact on all the mechanical parts involved. A further advantage is the increased contribution of the front axle to the overall traction, a condition that can be valuable, for example, when leaving the rows with heavy towing and wet soil. According to Kubota designers, the reduction in turning radius achieved is 18-20%. This is similar to what could be achieved by locking the inner wheel with the brake but with a much better respect for cità di sterzatura delle macchine, soprattutto per migliorare la transitabilità tra i filari, specie per quanto riguarda l’uscita e l’entrata nello spazio interfilare. Allo scopo, sono state individuate diverse soluzioni tecniche, anche piuttosto diverse tra loro e in parte assolutamente inedite nel campo trattoristico, ma che sono tutte accomunate dall’obiettivo di ridurre il più possibile il raggio minimo di volta. Quella che segue è una breve panoramica di ciò che attualmente offre il mercato, con particolare riferimento alle tecnologie di più recente introduzione. New Holland SuperSteer Sul mercato da qualche anno, sui trattori di New Holland dotati di SuperSteer l’asse anteriore è collocato in posizione particolarmente avanzata rispetto al vano motore, in modo che si possa ottenere un angolo di sterzata complessivo molto ampio (sino a 76°), grazie anche al movimento relativo di rotazione dell’asse stesso, in aggiunta a quello usuale delle ruote. Oltre a svolte a raggio ridotto, ciò comporta ovviamente anche un aumento del passo della macchina, tale che – secondo il costruttore – con il SuperSteer Capezzagne strette, talvolta anche chiuse da ostacoli naturali, rendono problematiche le manovre di svolta a fine filare Narrow headlands, sometimes closed by natural obstacles, make turning operations at the end of the row difficult
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