OSCILLATING WEIGHT (ROTOR)

The oscillating weight, sometimes called a rotor, is an essential component of self-winding mechanical watches. The oscillating weight takes the form of a half-disc (sometimes a little less) pivoting freely around its Axis. On the periphery of the oscillating weight is a segment made of heavy Metal (often Gold) aimed at increasing its moment of inertia. As the wearer moves, the oscillating weight is drawn toward the ground by the effect of gravity. The axis of the oscillating weight carries a pinion that drives the self-winding mechanism as the oscillating weight moves. The pivot point of the oscillating weight is generally positioned at the center of the Movement. As a result, the oscillating weight (rotor) covers the surface of the movement above which it moves. In this case, the automatic mechanism requires an increased thickness of the movement. Another construction consists of clearing a space in the surface of the movement for the automatic mechanism. In this case, the oscillating weight (rotor) only occupies a small surface area and keeps the construction free of any added thickness. When such small, off-center oscillating weights (rotors) are used, this is commonly referred to as a micro-rotor.