Case &Steyr go automatic
Case &Steyr go automatic
By Andy Collings
JULY sees production of a range of Steyr and Case tractors equipped with automatic transmissions start at St Valentin in Austria. First seen as prototypes at Germanys Agritechnica show last autumn, the range covers the 120hp-170hp bracket.
For Case there will be the CVX range and for Steyr the more logically designated CVT range – Continuously Variable Transmission. The UK will see Case bring in the 130hp and 170hp models while Steyr, through importer Bonhill Marketing, delivers the full pack with 120hp, 130hp, 150hp and 170hp versions. Front axle and cab suspension is available as an option or as standard on selected models.
All, however, are powered by 6.6 litre, 6-cylinder turbocharged Valmet engines.
The new transmission department is designed to provide stepless ratio changes from 0-50kph and, like other automatic transmissions – Fendts, for example – employs hydrostatic and mechanical drive mixed in a planetary gear system to achieve this.
But unlike other systems, the Steyr development also incorporates four mechanical speed ranges – an arrangement designed to allow a higher proportion of mechanical drive to be achieved and, as a result, greater efficiency.
When starting off the hydrostatic/mechanical drive ratio is 50%, which becomes 100% mechanical at 8kph when the first speed range is fully employed. As speed increases an input of hydrostatic drive is called for once more before the second speed range is engaged for 100% mechanical drive and so on through the speed ranges.
It can be seen that by using the four mechanical speeds the percentage of hydrostatic drive is kept to a minimum.
Automatic Productivity Management (APM), once it discovers what you want the tractor to do, is designed to set the most efficient engine speed and gear ratio for any particular operation.
The first point to note is that the accelerator pedal is not a throttle pedal – far from it. When it is depressed the APM computer senses how far and how quickly it has been depressed. From this information the optimum engine speed and gear ratio is selected.
At speeds below 20kph a cruise control can be employed which works in an identical way to a conventional car system – once a required speed has been achieved a button is pressed to set and maintain it. Need to go faster or slower then + or – buttons come in to play. Set speeds can be recalled should the system have been cancelled by pressing the brakes for a headland turn – headland speeds can be set separately if required.
A second mode of APM concerns pto operation – the tractors have 540/1000 and eco 540/1000. When constant pto speeds are required engine speed can be set and maintained automatically with gear ratios changing to accommodate different conditions.
Other modes include the ability to create a ground speed pto arrangement which calls for a gearbox ratio to be locked, with the result that changes in pto speed are in direct proportion to variations in ground speed.
Driving the CVT is interesting. In the field it is difficult to fault the system – its automation should lead to greater efficiencies both from the tractor and operator.
On the road though, pulling a heavy trailer or implement, the remote drive pedal operation, it seems, is not quite so user friendly. Bearing in mind there is no direct throttle or gear ratio control, attaining and sustaining a required speed seems tricky.
Perhaps familiarity will counter this problem but not being able to select and hold a lower ratio to create an engine braking effect when travelling down hill with a heavy load is not so easily overcome. The tendency is for the transmission to select the highest gear ratio – as automatics do – so that the dependency on efficient brakes becomes essential.
CASECVX ANDSTEYRCVT
Engine: Valmet 6.6 litre turbo.
Power: 120hp-170hp 4-models.
Transmission: automatic and stepless, braked at standstill.
Shuttle: Clutchless.
Sample price: CVX 170 £72,000.
Case CVX170 takes to the road…foot on the drive pedal and go.
Inset:Transmission exposed. Red denotes mechanical drive, green is hydrostatic. The four speed ranges which dog together at set speeds can be seen in the lower half. The yellow section, which is the transmission output, is where forward and reverse is selected.