17 November 1995

Transmission breakthrough

A TRANSMISSION which provides a stepless, variable drive, yet retains a high degree of efficiency, has been developed by Fendt.

Fitted to the companys new 260hp 926 tractor – a tractor which has the same dimensions as the 230hp 824 – the development is considered a breakthrough in tractor transmission technology.

Fendt is first to admit the system is not new, but the engineering involved clearly is.

Key to the system is the design of the hydraulic circuitry which comprises a pump and two motors. All can react to the tractors load requirement. Included in the system is a mechanical drive system, the hydraulic and mechanical systems working in unison.

Drive from the engine is split into two power lines – hydraulic and mechanical through a sun/planet/ring gear arrangement. The drive is initially to the planet gears with the sun gear the mechanical output and the ring the hydraulic output. Drive is reunited on a summary shaft before reaching the differential.

In operation, initial drive is taken up by the hydraulic circuitry through the variable speed motors. As speed increases a greater percentage is taken by the mechanical drive.

Complicated as it sounds, the result is that the operator can choose optimum rpm and then select the required ground speed for the task in hand. Further refinements include a cruise control where a selected working speed can be smaintained, virtually irrespective of engine speed and interruptions from headland turns.

In-cab controls comprise a single joystick which is simply pushed further forward for greater ground speed and pulled rearwards for reverse drive.

Single joystick control for the new stepless, variable drive system developed by Fendt for its flagship 260hp 926 tractor.