With the introduction of the individual wheel drive Liebherr presents its latest innovation to the reachstacker world. Based on the highly acclaimed hydrostatic transmission, such revolutionary feature offers outstanding opportunities like a minimizing of side forces on the steering wheels and a more effective driving gear.

In 2004 Liebherr brought its own reachstacker to the market which immediately caught both container terminal operators as well as drivers by several unique features like a curve-shaped telescopic boom and a fully hydrostatic transmission. Two years later the newcomer is well established in the market with more than 30 machines in operation in Europe, the Americas, Asia as well as Africa.

Why hydrostatic transmission?
There are in fact numerous advantages which convinced Liebherr to go for such unique drive concept when developing its own reachstacker:

- As a basic principle the hydrostatic transmission is characterised by a high power density which means small dimensions of components as well as small induced masses. This gives the reachstacker a fast acceleration and an extraordinary high efficiency factor.

- In contradiction to conventional reachstackers stepless acceleration and deceleration is implemented to the Liebherr machine as there are not any regulation steps. This does not only have a positive impact on the lifetime of various components but also adds to the driving comfort for the operator.

- Another feature of a hydrostatic transmission is its high output at already low revolutions, deriving from the earlier mentioned small induced masses. Furthermore it is characterised by a very good controllability.

- With conventional reachstackers the power pack can only be installed in the centre of the machine due to a centrally located differential gear. Unlike such concept, the hydrostatic transmission does not request any particular place of installation for the power pack but gives a free choice to the design engineer. Having made use of such opportunity, the entire power pack has been placed to the righthand side of the Liebherr reachstacker where service and maintenance staff experience incomparable access to all essential service points.

- The braking power can effectively be used for the "working hydraulics" and the basic load; furthermore such working hydraulics is not located behind the torque converter which again increases the efficiency factor.

- Last but not least the hydrostatic transmission is not only characterised by smaller but also less components. Obviously this has a positive impact on the service and maintenance costs as well as on the overall reliability of the machine.

Taking reachstackers...
With conventional reachstackers a rigid, non-steerable drive axle is used due to the high axle loads which occur. The drive axle is fitted with differential gears and planetary gears arranged centrally in the wheel hubs. These differential gears are driven either mechanically or hydrostatically. Service braking takes place via dry or wet-running multiplate brakes, the holding brake consists of a spring-loaded disk brake. The non-driven, steerable axle is used as the steering axle. A floating bearing is predominantly used to compensate for uneven driving surfaces. The wheels at the steering axles are fitted with, and partly without, a service brake or holding brake. The steering is carried out via one or more hydraulically actuated steering cylinders.

With such conventional design, there is the disadvantage of a high tire wear in the steering axle which in particular arises on pronounced steering movements as a consequence of the central drive and the inner friction in the differential gear. A differential lock is moreover required for the transfer of the drive power to the ground if one side of the driving axle is located on a slippery, smooth surface. Only conventional steering is possible due to the previously described axle support. Transverse driving, i.e. driving 90° with respect to the vehicle frame, and slanted driving, the so called "dog gait" are not possible. Only a limited manoeuvrability is hereby given. Moreover, due to the rigid axle arrangement, no height compensation is possible when driving on a sloped plane.

...into a new era!
With the implementation of the individual wheel drive, Liebherr's revolutionary innovation on the reachstacker market, individual wheel hubs with integrated planetary gears and hydrostatic drives are provided for the driven wheels. Every driving wheel or every pair of wheels can be controlled individually due to this solution. It is thereby possible to supply as well as to actively influence different drive powers to/at the respective drive wheels. Consequently it is manageable to build up a steering torque which supports the steering movement and the stability of the reachstacker. The lateral forces at the steering wheels can hereby be reduced almost completely - which certainly has a substantial impact on the lifetime of the steering wheels!

Another advantage is the reduced strain on the steering wheels and thus the increased running performance of the wheels. Furthermore, traction is also increased on a slippery, smooth surface due to this individual wheel drive as the wheels can be individually supplied with a maximum possible driving torque depending on the traction present. Even an antislip control for each individual wheel is possible!

On top of that the individual wheel drive adds to increased turnover figures at less cost: Since facing no time delay when steering more stability and less wobbling are to be noticed by the driver thus assisting him in achieving better turnover rates. And due to a more effective driving gear, less fuel consumption and less gear oil are being recorded by the service and maintenance staff!

By the way, the first reachstacker equipped with an individual wheel drive has just been delivered exworks Nenzing. It is currently on its way to the Howland Hook Marine terminal, being part of the New York Container Terminal, and will soon work along with four Liebherr ship-to-shore cranes which have been delivered within 2004.

About the company
Liebherr-Werk Nenzing GmbH is part of the Liebherr group presently comprising more than one hundred companies throughout the world and employing more than 22,000 people. Founded by Hans Liebherr in 1949, the Liebherr group is decentrally organised into corporate units of easily manageable size that operate autonomously. The Liebherr Group's holding company is Liebherr-International AG in Bulle (Switzerland), which is entirely owned by members of the Liebherr family.

Liebherr-Werk Nenzing GmbH was founded in 1976 and concentrates today on the design and manufacture of harbour mobile cranes, reach-stackers, ship and offshore cranes as well as duty cycle crawler cranes, lift cranes and foundation equipment. Further manufacturing sites, belonging to the Nenzing plant are located in Sunderland (Great Britain) and Rostock (Germany) as well as four fully owned companies in Hongkong, Hamburg (Germany), Amersfoort (Netherlands) and Niederhergheim (France). A total of approximately 1,700 employees are based at the various sites. In fiscal year 2005 the turnover of Liebherr-Werk Nenzing GmbH amounted to €443,8 million.

Contact Details:
Liebherr Werk Nenzing GMBH
Ph: +43 55 256 0606
Click here to visit Liebherr Online
Click here to send Liebherr an Email