17 November 2000

CVTCHALLENGE TO POWERSHIFTTRANSMISSION

Transmissions will feature prominently among the new

tractor developments at this years Smithfield Show, with

more of the leading manufacturers adding CVTs to their

options lists. Mike Williams reports

CVTs (continuously variable transmissions,) were developed in Germany, with Claas, Fendt and the transmissions specialist ZF all working independently to combine the benefits of hydrostatic drive with the efficiency of a mechanical gearbox. The result is a new type of transmission which is poised to provide the first serious challenge to the supremacy of the powershift for medium and high horsepower tractors.

It was Fendts Vario transmission which first established the benefits of a CVT. These include on-the-move stepless and clutchless shifting within each range, plus a joystick which also controls forward/reverse selection. Vario was available initially on the top model in the Fendt range, powered by a 260hp engine, but it has more recently moved down to the smaller and medium models.

There are now 11 Vario models, starting with 85, 100 and 110hp versions in the 400 series, plus four models from 115 to 160hp in Fendts 700 series, these will be making their first Smithfield Show appearance.

Collaboration

CNH, the Case/New Holland group, has also moved into the CVT tractor market. The S-Matic transmission arrived this summer on two models in the Case IH range and four in the Austrian built Steyr range. Steyr is part of CNH, and developed the S-Matic transmission in collaboration with ZF.

A special feature of the S-Matic drive is the control system, operated by the computer that also manages the engine. This allows the transmission to respond automatically to changes in engine speed and load, helping the driver to maintain the optimum engine and transmission settings.

S-Matic is available on Case CVX models powered by Sisu engines delivering 130 and 170hp and on the four-model Steyr CVT range with outputs from 120 to 170hp. Both ranges should be arriving in UK showrooms early next year, and they are likely to be high on the priority lists of tractor buffs visiting the Earls Court show.

John Deere is the newest entry in the battle for CVT sales. Their AutoPowr hydro-mechanical drive, based on a ZF transmission, will be announced at Smithfield Show and be available initially on four 6010 series tractor models covering the 105 to 140hp sectors.

AutoPowr offers stepless shifting and other benefits which helped establish the success of CVT transmissions, but the control system developed by John Deere has a number of special features. These include engine braking when lower drive ratios are automatically selected as the operator releases the foot throttle. AutoPowr also allows the operator to select manual, economy or power mode to match the requirements for the type of work the tractor is doing.

The introduction of John Deeres AutoPowr means the top three manufacturers in the global tractor industry all have CVT models in production. Fendt is part of AGCO, which also owns Massey Ferguson, and it would not be surprising to see a version of the Vario transmission in some MF models in the future. It would also be logical for the S-Matic transmission to spread eventually from the Case and Steyr ranges to their New Holland stablemates.

Meanwhile, improved powershift transmissions are being developed to compete with the increasingly popular CVTs, and these will also feature on the Smithfield Show stands.

First 200hp plus

Renault is showing the recently introduced Atles range, which includes the French manufacturers first 200hp plus models. At this stage there are three Atles models powered by Deutz engines producing from 190 to 240hp, but Renault has already hinted that a more powerful model is on the way.

The Atles transmission is a powershift supplied by Funk, a John Deere subsidiary. It is described as one of the new generation of intelligent transmissions because the way it operates is governed by the type of work the tractor is doing.

For heavy draft jobs, such as ploughing, the control system speeds up the gear changes to reduce the loss of torque and forward momentum and improve efficiency. But, for transport and other low draft applications, the shift speed is slower and smoother, to give the operator a more comfortable ride.

Another transmission development making its first Smithfield appearance is the SDS or sequential drive system from Same Deutz-Fahr. It was introduced last year on the companys Same Champion and Lamborghini Rubin models, and uses a CAN-Bus system to provide an electronic link between the powershift transmission, linkage, engine, control unit and dashboard display.

Using SDS the driver can pre-programme up to eight different sequential operations, which are stored in the control systems memory, ready to be activated when the operator presses a green button. The operations, which are carried out in the correct sequence, could be those needed to make a headland turn with a mounted implement on the rear linkage.

Transmission functions available for integration into an operations sequence by using the SDS programme can include forward/reverse changes and gear shifting, as well as engaging four-wheel drive and controlling the front and rear diff locks. &#42

Above: The new Steyr

CVT is available in Case and Steyr tractors in the 120 to 170hp range.

Left: CVT is available

on Deere 6010 series tractors from 105 to 140hp.

Below: The new

Renault Atles high

horsepower tractors

are equipped with

an "intelligent"

transmission.

Deeres Auto- Powr CVT transmission allows the operator to select manual, economy or power mode to match the

type of work being done.

Above: Fendts Vario gearbox was the first of the new generation CVTs.