How do automatic mechanical watches work?

Automatic mechanical watches use the wearer’s arm movements to rotate a built-in rotor, which in turn winds the mainspring using a gear system, storing power. The mainspring releases energy, which, through the gear transmission system, drives the escapement and balance wheel/hairspring system to operate stably, thus driving the hands to keep accurate time. No battery is required, and the watch can maintain its power by wearing it daily.

Core Principles and Components

Power Generation (Winding): The watch incorporates an eccentric weight (automatic rotor/oscillating rotor). When the arm swings, the weight rotates freely within the watch due to gravity.

Energy Transfer: The automatic rotor is connected to the mainspring barrel via a set of gears (automatic gear train), converting the kinetic energy of the rotation into the potential energy of the mainspring’s tension.

Energy Storage: The mainspring is wound up to store energy. To prevent overwinding and damage, automatic watches typically have a “sliding mainspring” (secondary mainspring), which slips within the barrel when fully wound, achieving automatic limit.

Timekeeping System: The mainspring slowly releases energy through the gear system, which is then transmitted in stages through the escapement mechanism. The frequency is controlled by the balance wheel and hairspring, driving the hour, minute, and second hands at a constant speed.

Key Features of Automatic Mechanical Watches

Battery-Free: Power is generated through daily activities; a fully wound watch can run for approximately 36-50 hours.

Rotor: The core component, capable of rotating 360 degrees (fully automatic) or oscillating 120 degrees (semi-automatic).

Thickness: Due to the addition of an automatic winding mechanism, automatic mechanical watches are generally thicker than manual winding watches.

Wearing Recommendations: It is recommended to wear the watch for at least 8-10 hours daily to ensure sufficient power reserve. If the watch is not worn for extended periods, manual recharging is necessary.