Step-free access to the terrain

Step-free access to the terrain

VDS is an engineering office in Wolfern near Steyr in Upper Austria. The company was founded six and a half years ago and specializes in continuously variable transmissions for tough off-road use. One product is the so-called VTP transmission (“Variable Twin Planet”). The system works with hydrostatic-mechanical power splitting. This means: in the purely hydrostatic performance range and, depending on the version, with up to three overlay ranges. The core element is a double planetary gear set at the transmission output. The reversing planetary gear is only active at low speeds in purely hydrostatic operation; in the second planetary gear, mechanically and hydrostatically transmitted power is superimposed. This arrangement results in high tractive force and large gear spread with little mechanical effort. The advantage is that low power is transmitted purely hydrostatically and high power or torque is transmitted both hydrostatically and via the mechanical part. 

The system is currently being used successfully, for example in small vans from the Swiss company AEBI, as well as in tractors with lower top speeds. But now they are also setting their sights on other divisions, such as off-road vehicles and off-road transporters. For this purpose, a so-called “demonstrator”, i.e. a pre-production vehicle, was put on the wheels in order to be able to show what the system can do. And it can do a lot convincingly. Even in difficult terrain, it takes little effort for the driver to control a vehicle equipped with a VTP transmission. Depress the accelerator pedal and you'll move forward. To stop, you simply take your foot off the accelerator - the vehicle is stationary, using the engine and transmission brakes, while the engine continues to run even when stationary.

Even drivers who are inexperienced off-road can get to grips with the system very quickly, as all they have to do is keep the vehicle on course and don't have to worry about any gear ratios, locks and the like. For operation on paved surfaces, the gear ratios have been designed so that a top speed of around 180 km/h would be possible, a value that the Land Rover Defender currently equipped with this cannot achieve due to its engine power. Another gag is the so-called free rocking automatic: at the push of a button, the vehicle jerks back and forth to free it from a mud hole, for example.

Available in two sizes

The transmission will be manufactured in the Czech Republic and will be available in two sizes: 170 HP and 1,000 Nm or 400 HP and 2,000 Nm. The costs are around 20,000 euros for the “small” gearbox. Managing director Heinz Aitzetmüller sees the customers primarily as emergency vehicles, for example from the fire department and (mountain) rescue, but also the military and individual private individuals who simply want to treat themselves to this “luxury”. We are now working on other projects in this area. 
Since the hydraulic part of the VTP transmission is susceptible to both heat and cold, it will be replaced by a controlled electric motor in the future 
substitute. (ff)