In many drive trains, rigid toothed pulleys are used to ensure the effective transfer of tractive forces in the direction of pull. However, this can lead to vibrations being transferred from the prime mover, via the pulley, to the transmission. The Geman sealing and vibration control specialist Freudenberg Simrit claims to have eliminated these vibrations by integrating a shock damper into the pulley.

This damper (shown below) consists of two elastomer elements connected to by a bridge. The larger elastomer element is designed to damp vibrations in the main direction of pull. The smaller element damps counter-vibrations. Depending on the application, three or four of these shock damper elements are integrated into a two-part belt pulley.

Simrit uses finite element analysis to analyse the forces that occur, the resulting rotation angles, and the maximum compression of the damping elements. This allows it to design shock dampers that meet the exact requirements of an application, and prevents damage to the elastomer elements caused, for example, by gap extrusion under high pressure as a result of excessive compression.

The simulations use specially developed material models that describe the behaviour of elastomer accurately. This ensures that shock dampers can be optimised rapidly for special belt drives.

In one early application, the damped pulleys are being used to reduce vibrations and wear in motorcycle transmission systems.

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