The Georg Müller GmbH is in the business of transporting heavy loads of various construction materials. A business that requires venturing into rough terrains. For economic and safe operation, the company relies on innovative Voith technology.
Power, strength and durability are attributes that immediately spring to mind to describe trucks that have to carry heavy loads of sand, gravel or timber. But sometimes the big muscles among the commercial vehicles are about something entirely different – a sensitivity that makes every inch count. Maneuvering in sand pits or on slippery dirt roads often requires sheer strength, but also highest precision. A fact that the drivers of the Georg Müller GmbH in the small town of Wilburgstetten, Germany, experience every day.
The family-run company quarries sand, transports logs and has a gravel plant. Eighty trucks make up the fleet, but for off-road operations owner Georg Müller and his wife, Bianca, rely on 10 Mercedes-Benz Arocs fitted with the Turbo Retarder Clutch VIAB (or simply VIAB for short) from Voith. The unique clutch technology combines hydrodynamic start-up and braking functions, which support the driver and preserve the drivetrain. The wear-free integrated start-up and braking system is an optional feature in the heavy-duty class of trucks at Mercedes-Benz. Though the initial costs are higher, the Müllers expect to make savings in the long run.
For slippery, steep terrain
“We have difficult terrain in the woods, in quarries and on construction sites – and often have to start a fully loaded vehicle on slippery grounds or on steep slopes. That means a high wear on the clutch. The vehicles are in use for eight to 10 years. In that time frame, you would normally have to exchange the clutch at least twice,” explains Georg Müller. “We chose to invest in the technology for economic reasons on the one hand, and also because it makes the work of our drivers easier and much safer,” adds Bianca Müller. The VIAB enables both sensitive and wear-free starting as well as maneuvering at the lowest of speeds – both important in many areas of the Müllers’ operation. Precise maneuvering with heavy loads is one example. “The VIAB was originally designed for Mercedes- Benz heavy haulage tractor units,” says Hans-Günter Böhm, Senior Global Key Account Manager Truck OEMs, Division Turbo. “Mercedes-Benz relies on this technology for its Arocs, Antos and Actros series of trucks. The Actros, for instance, has no difficulty starting at extreme inclines – even with a load of 250 metric tons. The combination of powerful engines with our retarder clutch enables a very spontaneous and dynamic start and quick response to acceleration – even at high total train weights.”
This kind of agility is highly appreciated by the drivers. Responsible for driving timber transports all over Germany, Tobias Glatter, one of the truck drivers at Georg Müller GmbH, has to deal with loose, muddy and even icy roads all year round. Driving in such conditions is not only difficult but can be dangerous if the vehicle were to start slipping, for example. “The VIAB is especially helpful in maneuvering the truck on difficult underground. The system is very sensitive, precise and stable. The truck is easier to handle in every terrain,” says Glatter. Martin Wunderlich, who drives a tipper for sand or gravel, agrees: “If you sink in a little on a construction site it is easier to get out again because the wheels don’t start spinning immediately. Driving with the VIAB is so easy. You step on the gas and the truck just runs.”
This is made possible by the unique design of the VIAB. The pump impeller and turbine wheel face each other in a non-contact configuration in the Turbo Retarder Clutch. The moving pump impeller is at the engine end, while the turbine wheel is installed at the transmission input. The power is transferred from the impeller and turbine without wear by automatic transmission fluid.
When the driver steps on the accelerator, compressed air pumps oil into the Turbo Retarder Clutch, establishing a non-frictional connection between engine and transmission input shaft. This form of power transmission offers the benefit of fast yet gentle and wear-free transmission at full engine torque.
Tough demands met
And the system is also easy on the brakes. During braking, the turbine wheel is locked in position and fluid is pumped into the housing once again – in this case it acts as an effective primary retarder. “With the wearfree braking system you can decelerate almost to a standstill. In any kind of difficult situation you always have full braking power because the service brake doesn’t run hot. This means that, if driven carefully, the vehicles go for 500,000 to 600,000 kilometers without having to replace the brake pads. This is around three times more than brake pads usually last,” says Georg Müller, and adds: “The demands we make on the vehicles are very high. They have to withstand stresses that are quite different to trucks that mainly transport goods on the highway. As a result, our demands on the technology are a little higher as well, and, so far, our experience has been very positive.”
Disconnecting to save
The next generation of the Secondary Water Retarder (SWR) from Voith – the ECO-SWR – takes the proven technology even further. Gunther Kraft, Vice President Truck OEMs, Division Turbo, explains how.
What are the main features that distinguish the ECO-SWR?
The main innovation on the ECO-SWR is that it can be disconnected from the drivetrain in idle mode. Located in the drivetrain of a bus or a truck, the rotor of the SWR is rigidly connected to it via a step-up gear train. So while not in use for braking operation it still runs, and it runs against air resistance in the circuit. Though the resistance is small, it consumes energy nevertheless. With the ECO-SWR this constant resistance and consequential power use is eliminated by a coupling that disconnects the rotor from the drive shaft in idle mode.
What are the benefits for your customers?
Apart from the yearly fuel savings, the new technology contributes to a reduction in CO² emissions. Not only is this beneficial to the environment, but it can also positively affect the CO² certification of the vehicles. As a result, both manufacturers and operators benefit. Manufacturers because they can optimize their overall CO² efficiency, on which tax subsidies are dependent. And the operators because they directly profit from the reduced fuel consumption, lower taxes and potentially toll charges.
And the driving experience?
The ECO-SWR offers great driving comfort and safety. Just as with its predecessor it is integrated into the vehicle’s brake management system. So the driver activates the continuous brake system as usual – either via the steering column or the brake pedal.