Accessories that Make a Difference

Tractors are often sold with accessories to improve performance – for example, front axle suspensions, on-board computers, advanced hydraulics, and special cab equipment – and they usually repay amply the extra cost

Accessories, often called 'optionals', may add significantly to the bill when buying a tractor, but the right accessories can amply repay their cost through the advantages they provide. There is a simple equation: if you want the extra devices and functions on top of what the standard tractor offers, you have to buy the accessory in question.
Top of the range tractors typically come these days with the possibility of extensive tailoring to suit individual needs. But this is no longer the prerogative of high-powered tractors. Even smaller models designed specifically, for example, for use in vineyards or orchards are normally offered with a varied list of possible accessories.
On high-powered models, one of the most widely sought after optionals is currently a front axle suspension. Some more or less experimental examples of the device were tried out in the 1950s, but they became generally available starting in 1994. They achieve a significant improvement in driver comfort and also reduce the risks of high-speed driving. The front suspension reduces the pitch and rolls typical of tractors towing heavy equipment by making a more effective contact between wheels and the road's surface. All manufacturers now have their own technological solutions, all based on one or more hydraulic or pneumatic cylinders linked to nitrogen-filled shock absorbers. Together with the valves controlled by an electronic control unit, they are sufficient to smooth out low frequency oscillation effectively.
Normally, the device can be disengaged for precision work. Often, one can also calibrate the vertical movement and the extent of reaction to dynamic shocks. If the front axle suspension is combined with active suspensions on the riving seat and/or the whole cab, comfort from vibration is guaranteed.
Comfort is not the only aim. Another of the most widely requested optionals is an on-board computer interfacing often with a touch-control monitor and the various electronic control units used by the tractor and the tools it powers, through the recently standardised communication protocol, ISO-Bus. The protocol means that a single terminal can control all the on-board parameters, reducing the space needed significantly and simplifying controls. The most demanding technological challenges include the joint management of terminals for the tractor, GPS navigation and the tools.
Another increasingly accepted optional, almost always installed directly in the factory before the tractor is delivered to the customer, is the front lift, often mounted with a power take-out. On top of the range tractors, very few are prepared to renounce this accessory, since it is important for effective combined operations, but also for easy management of heavy weights, which can be attached to the three-point hitch quickly and easily.
Starting out as a simple towing device, the tractor has long been a flexible central power source for which hydraulics have a central role. In addition to the ubiquitous rear lift, available optionals came down to an extra one or at most two power distributors. Evolution has been impressive, especially as regards the capacity of the primary pump. On many tractors available hydraulic flow can be increased by adding in part of the oil kept under pressure by the pumps for the auxiliary services.
The number and position of the power distributors has also varied. Four distributors used to be the usual maximum, all located at the rear. These days, you may get as many as eight hydraulic outputs, some of them located frontally to run front-mounted tools.
It is also possible to regulate the hydraulic flow to the individual distributors at will and to set the timing as well. This means that the amount of oil required by the tool is adapted to its tasks to perfection, avoiding excess pressure and modulating its effects more effectively.
Small-gauge tractors also come with a broad range of offers of optionals – perhaps, even more than for open-field tractors. In fact, if the jobs done by the latter are now more or less standardised, specialist tractors have top handle a wide variation of situations and require very extensive customisation.
Hydraulics are the most important factor. Oil flow and number of distributors rival much more powerful tractors. You may find as many as twelve, double-effect outputs to control all the hydraulic movements of rather complex devices such as toppers and defoliators. Joysticks have also been introduced to improve control speed, using a single ergonomically shaped lever for the commands referring to a number of distributors, activated by the joystick's movements or by the buttons on it. A proportional control is available on more recent models so the driver can regulate oil flow continuously, avoiding brusque movements in favour of gradual progression.
On specialist tractors, the cab is also often an optional. In fact, apart rom making a basic contribution to safety should the tractor turn over, closed cabs have recently ample acceptance on vineyard and orchard tractors because of the protection given to the driver when spraying or dusting – evidently, if doors and windows have excellent sealing and above all if a powerful ventilation system is fitted for adequate pressurisation inside and has active carbon filters to neutralise poisons from the products that could be sucked in with the incoming air. Specialist cabs also have rounded or aerodynamic contours to avoid catching on or damaging hanging shoots and branches.

BOX – The transmission is decisive
If a tractor is to move, the transmission or speed change cannot be considered as a real optional, but more as a variant. Manufacturers often offer two or more variants of a given model so that the machine can carry out specific tasks more effectively. The transmission must successfully combine the engine regime, which determines the regime of the power take-out, with speed and power production, in large part, the power input required to work the tool.
Only few years ago, some manufacturers were singing the praise of gearboxes with 64 gears forward and 64 in reverse. Naturally, the farmer never used all of them, but had a wide choice including the best one for the task at hand.
These days, in many cases, the number of available gears has been reduced significantly thanks to the introduction of power-shift gears with which the transmission ratio can be varied without touching the clutch. This means that resistance peaks in the job are no longer a hindrance.
The most recent evolution is the appearance on models with relatively limited power of continuously varying gears. These transmit power to the wheels in two ways, usually working in parallel: a traditional mechanical transmission and a fully modulated hydraulic one. Thanks to sophisticated electronic management, the tractor's speed can be optimised in great detail as a function of the task to be done, in complete independence of the engine regime.

BOX – Tyres, a working variable
Determining the best tyre pressure for any task a tractor may face is no easy matter. Evolving research suggests that to increase tractor performance and reduce soil compaction, the best choice is wider-section low-pressure tyres, which have a more flexible shape and reduce pressure on the soil. For highway use, however, the pressure should be higher, since this reduces tyre wear and fuel consumption, thanks to lower running resistance and improved driver control. It's now no longer impossible to change pressure quickly when making the transition from the open field to the highway thanks to a continuous pressure control kit. This involves an air distribution circuit, the air being produced by a compressor and held in a special tank. The heart of the device is a rotating distributor, which guarantees a correct link, under pressure and without loss, between the tractor and the moving tyres. A monitor in the cab shows the tyre pressure and can be used to regulate it. The common compressors installed on tractors can increase the pressure of all the tyres by 1 bar in about ten minutes.
Figbox02 - A rotating distributor in the wheel hub allows the driver to regulate tyre pressure directly from the cab, according to whether the tractor is to be driven in a field or on the highway.