The LuK testing tool allows you to perform the following tests on the DMF:
- Measuring the freeplay angle
- Measuring the rock
These tests, in combination with a visual inspection to check grease egress, thermal load, clutch condition, etc., allow for a reliable assessment of the DMF’s operational condition.
The freeplay angle is the angle at which primary and secondary mass can be rotated against each other until load is exerted on the arc springs. The measuring points are both end stops in the left-hand and right-hand direction of rotation. The measured freeplay serves as a wear indicator.
Some DMFs have a friction control disc that can be felt as a hard stop in one direction. In this case apply greater force to rotate the secondary mass a few more millimetres until spring resistance can be felt, and then allow it to return. This also rotates the friction control disc in the DMF.
The term “rock” describes the clearance between the two DMF masses which allows them to be tilted towards and away from each other