Harmonic damper

A harmonic damper is a device fitted to the free (accessory drive) end of the crankshaft of an internal combustion engine. It is essential in engines with long crankshafts (such as straight-8 engines) and is present on most engines as it reduces torsional vibrations that tend to peak at certain speeds. Torsional vibrations can greatly reduce crankshaft life, if not cause instantaneous failure, if the crankshaft runs at or through resonance. Because of this, dampers are designed with a specific weight and diameter to reduce mechanical Q factor, or damp, crankshaft resonances. Factory dampers are often re-sized in the same basic engine with any factory modification of crankshaft material, thickness, weight, or throw.