Method for measuring the damping coefficient of torsional-vibration dampers

A method for quickly checking the damping coefficient of torsional-vibration dampers that are filled with a viscous liquid and are provided with a swing ring, for purposes of quality control of a damper of a given nominal geometry that is being tested, comprising the steps of:

• determining permissible limit values .beta.'min and .beta.'max of a torsional-vibration damping coefficient, between which values the quality of the damper is acceptable;
• establishing a characteristic curve of a relation between the damping coefficient and the number of vibrations of the decay from a determined initial amplitude to a second determined amplitude within a freely oscillating torsional-vibration system into which the damper is fitted for the testing, having one degree of freedom, i.e. which system includes a disc that constitutes a mass and a torsional shaft that constitutes a spring with a given stiffness;
• tuning the system by changing one of the mass of the disc and the spring stiffness of the torsional shaft to achieve a well measurable relation within the range of interest between the damping coefficient and the number of vibrations;
• producing free oscillation with damping within the system with the damper fitted in so that the free oscillation takes place with the determined initial amplitude;
• measuring the number of the vibrations in the system upon the characteristic curve and taking the measured number as a basis between permissible limit values n.sub.min and n.sub.max to verify an acceptable quality of the damper, while an inferior quality is being declared at measured values that lie outside the limit values.