Venturing into rough terrains

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.

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.”