JUST WHEN we thought we'd seen everything in advanced tractor technology, along comes Fendt with unique features on its all-new 1000 Vario design.

The concept itself is different, of course - no-one has tried channelling more than 500hp through anything other than tracks, or four equal size wheels before. But Fendt wanted to produce a powerful tractor that could be lighter and more manoeuvrable than others with this power potential.

At the same time, running costs were high on the priority list, so there was much emphasis in the design process on how to put down all that power whilst also minimising fuel consumption.

Amongst the solutions are VarioDrive - the first tractor powertrain to drive the front and rear axles independently and to provide variable torque distribution - Fendt iD, which encompasses measures to drive all power-sapping components at lower than usual speeds; and VarioGrip, an on-board tyre pressure control system which also provides advice on pressure, ballast and speed.

To cope with exceptional hydraulic power demand, Fendt 1000 Varios can be equipped with a twin pump system using separate circuits to supply cylinders and motors at the most appropriate flow and pressure combination. And, for safety, they serve up an auto on/off mode for the electronic hand-brake and brake lights that illuminate above a pre-set rate of deceleration, regardless of whether the brakes are being applied.

Four models are in series production - the 1038 with peak output of 396hp; the 1042 with 435hp; the 1046 at 476hp; and the flagship 1050 peaking at 517hp. These outputs - plus peak torque figures of 1900Nm, 2100Nm, 2300Nm and 2400Nm generated between 1000 and 1500rpm - are provided by a new six-cylinder diesel engine from commercial vehicle manufacturer, MAN.

This marks the German company's return to the Fendt range some years after being ousted by Deutz power units, which remain in the rest of the ranges from the 500 Vario upwards.

The 12.4-litre MAN D2676 LE13x straight six engine has electronic common rail fuel injection operating at 1800 bar pressure and uses selective catalytic reduction (SCR) for emissions control without having to also resort to a diesel oxidation catalyst (DOC) or diesel particulate filter (DPF).

A variable geometry turbocharger, which has adjustable inlet vanes regulating the speed at which exhaust gases flow into the turbine, provides a wide torque band and quicker response to the accelerator pedal than a fixed turbo.

The Vario transmission, with its combination of mechanical and hydrostatic power flow, has been substantially uprated for this latest application. The working principal remains the same, though, with a wide-angle piston pump and two wide-angle motors delivering the flexibility of 100% hydrostatic drive at start-up and a linear progression to 100% mechanical drive at top speed.

However, there is no two-range gearbox as on lesser Fendt Vario tractors - the 1000 Vario performs all field work at speeds from 0.2kph and tackles road travel at up to 60kph in one range. The VarioDrive system also differs in that the hydrostatic drive motors are each dedicated to a single axle - one for the front axle and the other for the rear. This, together with some clever load and traction monitoring and clutch control, enables power and torque to be delivered individually to each axle according to need.

Flexible torque distribution is achieved through a T-piece located between the hydraulic pump and the hydraulic motors for the front and rear axles. It acts as a hydrostatic differential by permitting the oil flow between the pump and hydraulic motor to be adjusted freely.

As on the conventional Vario transmissions, the rear axle motor operates through a planetary gear set that variably brings together the hydrostatic and mechanical power routes. The front axle pump drives a shaft connected via a clutch to the front axle differential, with an 'intelligent' clutch in the four-wheel drive system allowing torque to be automatically and continuously transferred between the two axles according to need.

Drive to the front axle is automatically disengaged at speeds beyond 25kph or thereabouts to improve efficiency by reducing power losses through friction. And, since the variable four-wheel drive system eliminates the usual fixed ratio mechanical connection between the two axles, the 1000 Vario's front axle speed can be managed to pull the tractor through a tight turn - in the field this can trim the turning circle by up to 10%, whilst minimising tyre scrub wear.

Given the size of the new tractor's tyres, anything that reduces wear will be welcome! The IF 650/65R38 and IF 710/60R38 front covers would not look out of place on the back of lesser tractors but the big new Fendt gets either IF 750/75R46 or IF 900/65R46 tyres standing up to 2.35m tall on the rear rims, with the option to double up for maximum surface area.

The contact area these tyres provide can be optimised through good inflation pressure management - adjusting the pressure to the most appropriate for the weight they have to carry and the speed at which the tractor is operating, whether in the field or on the road. With VarioGrip fitted as standard, operators are encouraged to actively manage tyre inflation because all it takes is a 'click' on the Varioterminal touch display to activate the built-in air system.

Since tyre pressure can be adjusted on the move, there is no reason not to run the tyres at the higher pressures needed for fast road travel before bringing them down for high-draft field work or lower still for operations involving modest draft load.