There are of course various manufacturers of dual-mass flywheels. Some integrate supporting gearwheels, obviously for no other reason than as bearings, others use only bushes. What they have in common is that both, using several helical springs, mounted in the circumferential direction, brace both masses against each other. These can also contain smaller springs which generate a sort of two-spring effect, causing an incremental behaviour.

It is important that dual-mass flywheels are checked when ever a clutch repair is necessary, see the above figure. With the engine locked, the gearbox-side part of the flywheel is turned oppositely to the engine-side part. Here there are found, various reference values, sometimes beyond 20 °. Also important is determining the pivoting play by mounting a micrometer on the same lever arm. Values are permitted, depending to the type of drive, up to an astonishing 1.6 mm and more.

The range of application of two-part flywheels has been recently extended into the utility vehicle area, because coaches can be equipped with it to reduce gearbox noises. At the same time one hears rumours of an alleged repair frequency from certain passenger car manufacturers. Just when the friction clutch has, in many cases, equalled the engine service life, the problems with the flywheel begin... 09/08

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