A reaction mass and a spring are configured to form an “oscillator”. The reaction mass is coupled to, and can wrap around, a first pulley via a first belt/cable. The spring is coupled to, and can wrap around, a second pulley via a second belt/cable. The first and second pulleys are mechanically linked together and are mounted so they rotate in tandem. The diameter of the second pulley is different than the diameter of the first pulley to cause the reaction mass to travel a different distance than the spring in response to the up down motion of the reaction mass. The first and second pulleys may be circular with the second pulley being made smaller than first. Alternatively, the first pulley may be circular and the second pulley a cam of varying radius.