====== Weight segment ======
also //oscillating weight, inertia// (rotor)

A weight as heavy as possible, designed to wind a watch through the body movements of the wearer. The most common construction concept is either a [[central rotor]] or a [[micro-rotor]] (also [[planetary rotor]]). The rotations of the rotor then wind the movement of the watch automatically. (Therefore "[[automatic]]" watch).

There are single and bi-directional winding inertias. The first bi-directional winding mechanism of a watch was presented by [[Felsa]] with the [[Bidynator]]. Well known unidirectional winding calibres are the [[Valjoux 7750]] and the [[Lemania 5100]]. The calibre [[Rolex 3135]] (used for example in the [[Rolex Submariner]]) works by bi-directional winding.

Of great importance is the principle of the ball bearing [[central rotor]], developed at [[Eterna]].


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