VarioDrive

The innovation at the time mounted a major challenge to powershift supremacy in the medium and high horsepower tractor sectors, and Fendt was instrumental in extending CVT availability to smaller tractors as well as its larger tractors (up to 380 hp models) for the next 20 years. There was a new mountain to climb, however. The demand for larger tractors grew as farm sizes increased, but larger tractors in the industry were specialized tractors—four-wheel drive, articulated and large track tractors. Fendt could sell track tractors in Europe, but articulated 4WD tractors were too wide for the narrow roads of Western Europe. The challenge was to find a solution to get high horsepower equipment down the road for transport and get enough traction to the ground. While CVT systems had a high degree of automation to control the interaction of engine and transmission, they were not yet designed to deliver traction efficiency between tractor wheels and the ground. They also had not been integrated with 4WD systems, and could not influence the torque ratio between the front and rear axle, which is usually fixed on conventional 4WD tractors. At the 2007 Agritechnica farm machinery trade fair in Hanover, Germany, the star of the show was the unveiling of the prototype Fendt TriSix tractor.

This milestone has allowed Fendt to extend its standard tractor portfolio up to 500 hp and supply a hyper-efficient CVT transmission that easily transfers power to the

The solution was going beyond a CVT to a system that involves the whole drivetrain, including the axles and the 4WD system. By being able to distribute torque between the front and rear axle, power conversion and power distribution are merged to achieve optimum traction efficiency. The VarioDrive has one hydraulic pump and two hydraulic motors. The first motor is directly connected to the pinion shaft of the rear axle. The second is connected to the front axle. For high efficiency in transport, the second motor is disconnected by a clutch to avoid idling losses, and no range shifting is necessary. The front axle and rear axle are connected by an intelligent 4WD clutch which acts as an inter-axle differential lock. The 4WD is fully automated—on and ready to perform—allowing operators to concentrate on their work and never again forget to turn on the 4WD before a critical situation. As the engineers designed the VarioDrive innovation, the challenge of getting power effectively to the ground was met with one of the main innovations mentioned above: connecting the second hydraulic motor to the front axle to provide high torque at low speeds. When it came to designing the larger 4WD tractors VarioDrive made possible, Fendt needed a new range of tires that were row-crop capable. Putting 54-inch (1.37-meter) tires on 500 hp tractors had never been done before. Customers have the option of using very high flexion (VF) tires with the optional factory-installed Fendt VarioGrip CTIS to set and control tire pressure from the cab, which can reduce compaction while in the field, improve ride quality whether roading or in the field and reduce tire wear. Once all was designed, Fendt product management took on the challenge of convincing a large market that we could do more jobs or tasks with a single Fendt Vario tractor than with a large, articulated 4WD. Mission accomplished!

Fendt solved the transmission problem by splitting the engine power over two Vario ML 560 CVT transmissions. One transmitted power to the front and mid axles, the other transmitted power to the rear axle, which was subjected to heavier loads than the other axles. The idea was to enable the tractor to move between fields while being narrow enough at only 9 feet (2.7 meters) in width to adhere to European road regulations. The top speed of the tractor was 50 mph (80 kph). While the TriSix was never produced commercially, the concept was a major step on the way to the invention of an advanced new transmission concept—the continuously variable drivetrain or CVDT, known as the ML 400 or the TA 400 that became what is today known as the Fendt VarioDrive. This milestone has allowed Fendt to extend its standard tractor portfolio up to 500 hp and supply a. hyper-efficient CVT transmission that easily transfers power to the ground and minimizes slip for the Fendt wheel and tracked tractors.

As the Fendt designers set out to adapt the transmission and drivetrain innovations of the TriSix to the layout of standard tractors, they needed to solve challenges their customers faced with their current tractors. The goals included:

1. Design a high-horsepower machine in standard tractor layout that had large tires on the rear axle and a suspended front axle. This meant a compact design of the new drivetrain and a transaxle that could carry high loads on the rear wheels.
2. Design a versatile tractor with a high payload that allowed room for adequate allocation of ballast. The transaxle needed to be designed for high traction as well as high transport speeds.
3. Small turning radius.
4. Efficiency was important. For the new low-engine-speed concept that used less fuel to work, the drivetrain had to have high torque capability.
5. Include a central tire inflation system (CTIS) to boost traction efficiency.
6. A tractor that increased ease of use for the operator. That meant eliminating the need to manually switch the 4WD on and off, and providing a single gear range.
7. World-wide demands were considered, including the use of dual or triple wheels and the possibility of 30-inch (76-centimeter) for row-crop configurations.
   

As the engineers designed the VarioDrive innovation, the challenge of getting power effectively to the ground was met with one of the main innovations mentioned above: connecting the second hydraulic motor to the front axle to provide high torque at low speeds. When it came to designing the larger 4WD tractors VarioDrive made possible, Fendt needed a new range of tires that were row-crop capable. Putting 54-inch (1.37-meter) tires on 500 hp tractors had never been done before. Customers have the option of using very high flexion (VF) tires with the optional factory installed Fendt VarioGrip CTIS to set and control tire pressure from the cab, which can reduce compaction while in the field, improve ride quality whether roading or in the field and reduce tire wear. Once all was designed, Fendt product management took on the challenge of convincing a large market that we could do more jobs or tasks with a single Fendt Vario tractor than with a large, articulated 4WD. Mission accomplished

Fendt VarioDrive was developed specifically to exploit high engine power to keep speeds low, independent of ground conditions. Fendt VarioDrive enables a permanently on, variable four-wheel drive on higher horsepower Fendt tractors, allowing torque to be distributed over two transmission outputs independently on both axles. With the help of an intelligently controlled four-wheel clutch, torque can be shifted between the axles according to need. We call it Fendt Torque Distribution. During field operations, torque is transferred flexibly to the axle. The result is tremendous pulling power. As the speed increases, a clutch completely decouples the front axle drive at approximately 15 mph (24 km/h), eliminating drag losses in the drivetrain and increasing efficiency. Since there is no fixed drive ratio with the variable 4WD, the frontwheel drive can actively pull the tractor into a curve—the “pull-in turn effect.” This effect alone reduces the turning radius in the field by up to 10%.

Operators of Fendt track tractors benefit from a stepless VarioDrive CVT—the industry’s first CVT in a tractor with this level of horsepower. The VarioDrive CVT transmission allows for no range changes, optimizes engine power and maximizes fuel efficiency. In the Fendt 1100 VMT Series, the MAN engine and stepless CVT transmission pair together to automatically regulate and optimize the engine speed to deliver the required amount of power needed, whether going 65 feet (20 meters)
per hour or 25 mph (40 kph). The transmission provides optimal coordination with the engine for peak performance and productivity across multiple applications. Use of the Fendt VarioDrive technology has been expanded to other brands of AGCO tractors, and our leadership in transmission innovations won’t stop here. Stay tuned for more from Fendt.