Hydraulics for the beet harvester

The sum of the new developments makes the Tiger 5 a highly efficient working machine for beet farmers and contract harvesters.
Marginal Column

November 2015


The Tiger 5 is Ropa’s top-of-the-line model in the range of full-function harvesters for sugar beets. This giant, 15 meters tall, provides convincing qualities with its stepless drive train and, thanks to the hydraulics, is sure-footed even on slopes.

617 horsepower with displacement of 15.6 liters, 40 kilometers per hour as the top speed when empty, curb weight of 33 tons, and a payload of more than 30 tons. This performance data makes the Tiger 5, built by Ropa Fahrzeug- und Maschinenbau GmbH, the top model in its sector. Unique among the three-axle beet harvesters are the stepless travel drive and automatic, hydraulic slope compensation. This is enough to impress even experts in the field. In February, at the French SIMA trade fair for agricultural technology, the harvester was crowned the “Machine of the Year 2015” in its category. This prize is deemed to be the “Oscar in Agricultural Technology”.

Stepless gearbox: Travel drive with no break in traction

The 617 horsepower output by the engine is transferred by a stepless gearbox developed in a cooperative effort by Ropa, the Omsi Transmissioni S.p.A gearbox and axle manufacturer in Italy, and Bosch Rexroth. Michael Gruber, sugar beet technology department manager at Ropa, located in Herrngiersdorf, Germany, notes: “We wanted to top every competitor with our new development. This has been successful thanks to a hard-hitting trio made up of three renowned companies.” As early as four weeks after the kick-off meeting, the draft concept for the drive was completed. The “Constant Variable Ropa Gearbox” (CVR) comprises three hydraulic motors on the compound gearbox. It is located between the engine compartment and the third axle.

The very special feature here is the interaction of the two adjustable motors with a constant-speed motor. To achieve maximum traction force, all three motors work together when starting to move the machine. In order to increase the travel speed, the first adjustable motor is swivelled toward zero. Once it has reached zero, it has reached its velocity limit and is decoupled using a wet, multi-plate clutch. Since the motor is no longer being rotated, it causes no losses. To increase travel speed even further, the second adjustable-speed motor is also swivelled toward zero, but remains coupled. Thus, at maximum travel speed, only the constant-speed motor is active in the drive train. Thanks to the larger slewing angle and the lower throughput losses, its efficiency is higher, saving fuel for the user.

Such efficient power transmission results in amazing performance values. While the Tiger, during field work, is limited electronically to a maximum of 18 kilometers per hour, it can move on the road, from field to field, at top speed of 40 kilometers per hour – entirely without shifting and interruptions in traction. The Tiger travels at top speed with the engine turning at a thrifty 1,195 rpm. In the field, it runs beginning at 1,100 rpm during harvesting. The developers very consciously wrote this low engine speed into the specifications to achieve lower consumption values.

Just pressing a push button causes the Tiger 5 to convert, fully automatically, from the on-road to the off-road mode. The unloading conveyor, the ring elevator, bunker augur, and other groups unfold in sequence – monitored by sensors and driven by hydraulic motors. When compared with its predecessor, this all takes half the time.

Safe at every stance

Developed specially for the Tiger 5, Ropa has engineered a hydraulic chassis system with an oscillating front axle and two rear axles with hydraulic suspension. When compared with conventional three-axle harvesters where the center axis is bolted to the frame, the machine’s tendency to sway is reduced by two-thirds. This is effected by the hydraulic connection of the stabilization cylinders on the front and rear axles at each side. This also improves the way the harvester follows the rows and keeps penetration depth more uniform.

The beet harvester works masterfully even on difficult terrain. Thanks to six sensor-controlled hydraulic cylinders, the entire vehicle is tilted toward the slope by ten percent and thus kept in the horizontal. The compensation, effective in both directions, offers several advantages. Operation is more comfortable for the driver, since he always sits upright. And the vehicle itself is safer because even in extreme topography the Tiger remains stable, despite the higher beet bunker, while other harvesters would have long since tipped over.

The sum of new developments makes the Tiger 5 a highly efficient working machine for beet farmers and harvesting contractors. Customers – in markets all around the world – attest to its reduced operating costs at increased daily performance. That, too, is a product of the time-tested interplay of Ropa, Omsi and Bosch Rexroth.