14 May 1999

Technical tour de force…

Many more farmers and

contractors will be able to

put Fendts novel Vario

hydro-mechanical drive

system to work thanks to

the new Favorit 700-series.

Peter Hill gets a

transmission technology

update from behind the

wheel of the 160hp

Favorit 716

IF nothing else, the Vario hydro-mechanical transmission offers a new level of tractor security. Even if the cab has been left invitingly unlocked and the ignition key is in place, it is doubtful whether anyone, other than a student of the Vario operating manual, could fathom out how to get a Fendt Favorit 716 to budge.

Its all so different from anything else. There is little point searching for a gear lever to shift, because there isnt one. Theres no point, either, moving the joystick control without knowing what needs to be done to activate and operate the system.

Tempting as it is to appear knowledgeable by revealing these details, its probably best not to tempt fate. Owners of Favorit 700-series tractors will, after all, be keen to keep hold of them.

This tractor range – just two models at present – represents the anticipated move down the power scale for Fendts unique Vario continuously variable transmission. The bigger and heavier 900-series already caters for those in the 170hp to 260hp power league; these two come in at 140hp and 160hp.

In operating principle, the transmissions are identical. In structure they differ in size and weight and the use of just one, rather than two, variable output hydraulic motors for the newcomers.

The features that make the Vario design a practical proposition for tractors are the way hydraulic and mechanical drive is variably combined through an epicyclic gear unit, and the way a new design of variable displacement hydraulic pump and motor deliver a greater output range than hitherto.

Independent tests, comparing Favorit 900 Vario and Favorit 800 tractors, have shown only the slightest efficiency disadvantage, which is more than made up for by the lack of restriction of working speeds, the automatic speed control functions (which can prioritise ground speed, pto speed or engine power or economy), and the sheer ease with which Vario tractors can be driven.

Having got to grips with getting the tractor to move off, speed up, slow down, come to a halt and change direction, the real challenge for drivers new to the system is how to make best use of its boundless features.

To that end, the Variotronic control and information system, housed in an adjustable oval pod on the instrument panel, gives 700-series drivers more chance of doing so than those of the less informative 900-series. Variotronic offers graphical representations of the features and settings selected, the options available and, to some extent, the way the engine and transmission is behaving in response.

Most uncanny of these, perhaps, is the way a gentle turn of a dial can speed up or slow down the tractor. In practice, this would be used to select a precise working speed for the Tempomat cruise control feature.

This can memorise sufficient speeds for headland turns to be completed with little more than a sequence of joystick nudges – slowing for the turn; reversing; going forward again; accelerating to working speed.

The ultimate advantage of the lack of gears (save for field and road ranges) is where speed fine-tuning has particular benefits. Such as stone/clod separation and potato harvesting, when keeping webs and star rollers loaded just right can make a big difference to overall performance. Road haulage, especially given the Favorits 50kph top speed, should also gain from the system – though it is as well to rehearse the best procedures for slowing down in case a panic reaction has the tractor standing on its nose and the car behind buried into the back of the trailer.

There are several options – slow gently using the exhaust retarder (operated by a floor switch like an old-fashioned headlamp dipper); slow more quickly using the oil immersed disc brakes (though this lacks engine-braking effect); slow dramatically by wanging back the Vario control lever while on maximum response setting.

Either of the first two are recommended since, as the tractor slows, the transmission will automatically adjust ready to speed up again. With practice, the Vario controller can be used effectively and safely and this – as well as using the retarder – will avoid excessive disc brake wear and tear.

Easy as it is to consider only the transmission, the Favorit 700-series marks several other firsts for Fendt. The overall construction, for one, which comprises a cast frame for the front half of the tractor.

Apart from providing greater strength for carrying front-mounted implements or a hefty front loader, this provides ready mountings from the new front axle suspension, and relieves the engine of its role as a stress-bearing component. Also, because the motor is coupled to the Vario transmission unit by shaft, the cab is more effectively isolated from engine-derived noise and vibration.

The power unit itself also marks a first, being the only four-valve per cylinder diesel engine to see service in a farm tractor. Fendt is the sole user of this latest Deutz liquid-cooled engine, the multi-valve arrangement being more complex but giving the pay-off, apparently, of better breathing, power and torque characteristics.

Compared with the MWM-engined Favorit 514C of equivalent horsepower, the Favorit 714 Vario delivers 13% more peak torque, with a steeper torque response curve. And power delivery shows the now familiar increase in output as revs are pulled back from the 200rpm slower rated speed.

Other improvements include a 28% increase in oil volume – to 45 litres – to help fill large rams on tipping trailers, and a 24% increase in rear linkage lift, where the main novelty is the way the hydraulic cylinders lie beneath the cab and pull, rather than push, the lift arms.

FENDT714 VARIO

&#8226 Engine: Deutz liquid-cooled 5.7 litre 6 cyl turbo ic with 4 valves/cylinder.

&#8226 Power: 140hp at 2100rpm.

&#8226 Torque: 632Nm at 1400-1500rpm.

&#8226 Transmission: Vario hydro-mechanical CVT with two range gears – 0-30kph; 0-50kph and power shuttle.

&#8226 Hydraulics: Load-sensing variable output; max flow 102 litre/min at 200 bar (2900psi); volume 45 litre.

&#8226 Power take-off: Three-speed rear, two-speed front.