Tech Briefs
Multi-ribbed belt for twelve- cylinder engine

The new multi-ribbed belt developed by ContiTech has been approved for the twelve-cylinder Mercedes-Benz engine.

Contitech Antriebssysteme's multiple V-ribbed belt for the new twelve cylinder engine in the Mercedes-Benz CL 600, S 600, the forthcoming SL 600 successor, and the Maybach luxury model had to pass some tough tests with regard to belt flex, stretching resistance, and inherent damping properties.

The newly developed seven-rib belt must last for at least 160,000 km (99,400 mi) according to Daimler- Chrysler specifications. It must also be able to withstand extreme temperature fluctuations ranging from -40° to +120°C (-40° to +248°F). Additional belt stressing is generated by modern cylinder cutoff technology that causes so-called non-uniform crankshaft operation, exposing the belt to greater wear. A special polyethylene/propylene compound contributes to the belt's wear-resistance. In addition, minimized stretch helps reduce maintenance work and expense. The 2345-mm (92-in) belt is exposed to high loads due to its driving several underhood units, including the refrigerant compressor for the air-conditioning system, the pump for the active body control, the generator, and the water pump. Deflection pulleys and a tensioning idler are further elements across which the belt is fed. The application demands an extremely high degree of fatigue strength under reversed bending stresses.

DaimlerChrysler engineers also attached great importance to comfort aspects. ContiTech counteracted belt vibrations by designing its product with built-in damping properties. Large vibration amplitudes would promote belt wear. Belt noise has also been minimized. Cotton flock applied to the pulley side reduces slip as the belt enters the pulley and thus lessens belt-emitted noise.

An armor-plated vehicle is already being produced with a slightly shorter 2337-mm (92-in) version of the belt. A slightly longer 2760-mm (109-in) belt featuring ten ribs across its width is due to be used in the Maybach in 2002.

Jean L. Broge