This invention pertains to induced vibration and the dampening of these vibrations in the motor means. Vibration induced by rotating a shaft having eccentric weight thereon has been used to produce all kinds of shaking apparatus including large car shakers in which the induced force may be as much as...http://www.google.co.uk/patents/US4583414?utm_source=gb-gplus-sharePatent US4583414 - Vibration dampening apparatus for motor actuated eccentric forces
