Mobile breakers by RUBBLE MASTER: Extremely powerful even in the tightest spaces

HYDROTRAC GFT 8000 drive units by Rexroth at the core of complete travel drives

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Mobile breakers are put to work directly at the construction site to recycle concrete, asphalt and other materials into granules or to process natural stones. The Linz-based company RUBBLE MASTER has established itself as worldwide market leader for these mobile and compact machines using drive units from Rexroth in its travel drives.

Since two hours, the excavators have been loading freshly dug up asphalt into the RUBBLE MASTER mobile breaker, which produces a homogeneous, directly reusable end grain. Now the edge of the asphalt is so far away that an excavator operator reaches for the remote control and drives the mobile crusher a few hundred meters closer, while it continues to work. This means that the excavators only have to travel shorter distances. This increases productivity and reduces fuel costs.

Road transport without special permit

Mobile crushers by RUBBLE MASTER are used at large construction sites for on-site recycling or processing of natural stone. They save numerous of trucks loads to and from the site and thereby cutting logistics costs significantly. They turn a cost factor - the disposal of construction rubble - into an added value. Your advantage over stationary equipment: they can be simply loaded onto a flatbed truck and driven to various location sites. “Even our newest and strongest model, the RM 120GO!, is only 3.20 meters tall, and thanks to its small size, it is not subject to any special regulations that would apply to oversized machines,” explains Gerhard Etlinger, Deputy Technical Manager at RUBBLE MASTER HMH GMBH. Trucks carrying these compact mobile crushers are able to pass under all standard bridges.

At the sites themselves, ranging from narrow inner-city locations to rough mountain terrain, the operational weight on tracks of the mobile crusher range in six model sizes from 12 to 35 tons. The low height of the crushers severely restricts the available space for the travel drive. “When designing the chassis, we often work together with Rexroth to determine the technical limits so that the required performance and long lifespan can be combined in a very tight space,” emphasizes Gerhard Etlinger. Founded in 1991, RUBBLE MASTER builds crushers, screen units, and stockpile and conveyor belts. It is currently converting the majority of its travel drives to the new HYDROTRAC GFT 8000 drive series from Rexroth.

GFT 8000: Ten percent more torque

This modular series combines two- or three-stage planetary gear units with axial piston motors into a customizable drive package for mobile machines. In combination with Rexroth's most recent series of fixed and variable displacement motors, the drive units produce an increase in torque of around ten percent over the previous series. As a result, OEMs can improve driving performance with a drive unit requiring the same amount of space, or they can use a smaller unit and keep the performance the same. The newly developed GFT 8000 series covers drive torques from 10 to 130 kNm in nine steps.

At RUBBLE MASTER, the travel drive has two stages and reaches speeds from 0.6 to 2 km/h. For mobile crushers, these are very high speeds. “Recently, a customer in the Alps had to move the vehicle a few kilometers, it makes a huge difference whether it can go 0.6 or 1.8 km/h,” Gerhard Etlinger points out. Two gearboxes per vehicle drive the tracks. In collaboration with Rexroth, RUBBLE MASTER specified the current largest 35-ton gearbox model with a maximum output torque of 49 kNm. "The first commissioning was carried out together in the field," recalls Gerhard Etlinger.

Complete solution with electronics and software

An A10VO axial piston variable pump provides oil to the open circuit at 315 bar by controlling the flow pressure. The M4-12 load-sensing control block configured specifically for RUBBLE MASTER consists of standard valve discs with a special inlet element for switching from travel drive hydraulics to implement hydraulics. The travel drive features A6VE plug-in motors and an integrated braking valve. A customized software on the BODAS RC controller was programmed by Rexroth in accordance with RUBBLE MASTER's requirements. The control unit including the software and the parameter set goes directly from Rexroth to the RUBBLE MASTER assembly line.

The control unit receives information from the higher level machine control unit via CAN-Bus and controls the switching and proportional solenoids accordingly. The control unit monitors the correction function via switching position sensors at the inlet element and the two drive axles at the control manifold and switches the drive in case of problems in order to prevent dangerous situations. Moreover, in emergency mode, the proportional solenoids for the driving mode can be controlled via the switching inputs if the vehicle control system fails or the CAN-Bus signal is missing. The hydraulic motor with the integrated braking valve brakes the machine hydrostatically and activates/deactivates the multi-disc stop brake in the gearbox for a safe standstill. The braking valves integrated in the hydraulic motor protect the motor against cavitation and overspeeding when driving downhill. The desired braking behavior is customized for the machine by making adjustments to the valve.

The travel drive is equipped with hydraulic load sensing to ensure a synchronous operation of the two tracks and to prevent a track from spinning. The cabin-less machines are operated by remote control. Therefore, it is even possible for an excavator operator who is feeding the machine to move the mobile crusher directly from the excavator cabin by way of two joysticks.

Innovation focus on simple operation

RUBBLE MASTER has already sold several thousand mobile crushers around the world. Innovations such as the RM GO! principle are an important factor in the company's secret to success.  “The top priorities are intuitive operation, the reduction of service processes, and cost savings,” Gerhard Etlinger emphasizes. Moreover, this approach includes troubleshooting support via the software, as well as bundled maintenance intervals for all lubrication cycles. Moreover, all service points are centrally accessible from the ground.

The company invests heavily in technical innovations and operates around the globe with over 70 distribution partners. The yellow machines are visible from afar and marketed on all continents. Aside from the core markets Central Europe and North America, the mobile crushers are also sold in Eastern Europe and Russia, Near East, Asia, Africa, South America, and Australia. For already 25 years ago the company had developed a disruptive business model: “We have created our own market by generated added value through mobile construction rubble recycling,” Gerhard Etlinger explains. This concept was successful, and RUBBLE MASTER has been the worldwide market leader for compact mobile crushers for many years.