How do automatic watches produce energy? Storytelling by a watchmaker in Rome
An automatic watch has a rotor that provides energy to the watch movement, when the watch is worn.
A rotor is a circular sector, heavier on the external band so as to increase the moment of inertia. Each wrist’s movement generates a rotor rotation around its own axis and, through additional wheels, provides energy to the charge spring.
You can find both unidirectional and bidirectional charge systems: in the first case the rotor activates the spring only when rotating on one way (as in Patek Philippe watches). In the second case an inverter mechanism allows the charge in both ways (as in Rolex movements, where red inverters are easily recognizable, and in IWC movements with the special Pellaton recharge system).