Turn of stepless transmission to step forward

17 November 2000

Turn of stepless transmission to step forward

By Andy Collings

LAST year it was front axle suspension which grabbed the attention of the tractor developers.

This year it is the turn of the stepless transmission.

Latest contender for this seemingly important option is John Deere, which, following the lead of Fendt, Claas, Case and Steyr, has launched AutoPowr.

Available for four models in the companys 6010 Series range, the system is reported to be the result of four years development work with transmission manufacturer ZF, with John Deere designing the units operating software.

Like other stepless transmission designs, AutoPowr uses a combination of hydrostatic and mechanical drives; the trick is to try to ensure the maximum percentage of the more efficient mechanical drive is used at any one time. The ZF box uses four speed ranges for this purpose.

Controls comprise a column mounted lever, a transmission mode selector knob and a lever for speed control. The column lever can be set in forward, reverse, power zero – a position which locks the tractor when stationary – neutral and park, while the side-mounted selector knob allows the operator to select manual, economy or power transmission mode.

The speed control lever, with its dogleg allows a two-speed range to be selected, a slow range for field work and faster speeds for transport, for example. A small wheel on the top of the speed lever enables forward speed to be fine-tuned, which could be useful when harvesting potatoes. To describe the action of the transmission is more difficult than to operate it. In fact, when compared with several other stepless transmission control systems, the John Deere version is remarkably simple to master.

With the column lever in forward and the mode knob set at economy the throttle is opened and the tractor moves off. If the throttle is fully opened the tractor will accelerate using the transmission to ratio up. Once the set speed – set on the speed lever – is reached, engine speed will automatically reduce to select the most economical ratio and engine speed combination.

In other modes cruise control can be set which maintains constant engine speed for pto work with the ratios selected accordingly, while variations on the selector knob provides for different amounts of engine speed fall before lower ratios are selected within the transmission.

An interesting feature of the transmission is for it to detect when a reduction in speed is required, such as when drawing to a halt at traffic lights. Releasing the throttle initially slows the tractor but a touch of the brakes sets in a series of down changes in ratios to provide a useful amount of engine braking.

But those looking to enjoy the saloon-type driving the AutoPowr provides will also appreciate that luxury is not without cost. The option adds another £8625 to the basic price of 40kph versions and £7316 to 50kph models. &#42

Above: AutoPowr stepless transmission is now an option for John Deeres 6010 Series tractors. Right: Control detail – two-stage speed lever with fine tuning wheel. Note also the mode selector knob.

Smithfield will see John Deere launch a new range of trailed sprayers – the 800 Series which feature improved spray booms, universal drawbar and 50kph approved axle suspension. Three models offer capacities of 2400, 3200 and 4000 litres and boom widths from 15m to 30m. Triple folding booms with widths from 24m to 45m will be available next year.

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