Automatic watches are a true symbol of human ingenuity and mechanical precision. But have you ever wondered how an automatic watch works?

In this in-depth guide, we'll explore the mechanisms that allow these little horological masterpieces to spin without ever needing a battery or manual winding.

The basic principle of the automatic watch

Before diving into the technical details, it is essential to understand the basic principle on which an automatic watch is based. The heart of the system resides in the mechanical movement which is powered by a spring. This spring stores the energy needed to operate the different parts of the watch and thus give the time with precision.

The great particularity of automatic watches is the way they manage to keep this spring under tension. While classic mechanical watches need to be wound regularly to function, automatic watches use the energy generated by wrist movements to recharge.

The rotor: key element of the automatic watch

The secret of this automatic recharge lies in an element called rotor. The rotor is a moving part that can rotate freely around a central axis. Thanks to this freedom of movement, the rotor is able to follow the movements of the wrist and thus convert this kinetic energy into mechanical energy to wind the spring.

Rotor operation

In practice, when you move your wrist, the rotor rotates around its axis. These rotations make it possible to actuate a system of gears which will transfer mechanical energy to the main spring of the watch. It is this tension in the mainspring that will then allow the watch to run smoothly and accurately.

It is important to note that the automatic recharging system of the watch is not unlimited. When the spring reaches its maximum tension, it cannot be wound any further by the rotor. At this point, additional wrist movements will have no impact on the watch's power reserve.

The other essential elements of an automatic watch

In addition to the rotor and the mainspring, several other components are necessary for the proper functioning of an automatic watch. Here are some of the essentials:

• The pendulum: it is an oscillating part that regulates the speed at which the energy of the spring is released. By performing regular oscillations, the balance wheel guarantees precise measurement of elapsed time.
• The exhaust: this complex set of mechanical parts is responsible for transmitting the energy from the spring to the balance wheel. The escapement plays a crucial role in the regularity and precision of the watch.
• The gears: the gear system is essential to transmit energy from the rotor to the main spring. In addition, it also makes it possible to operate the various hands of the watch (hours, minutes, seconds) according to the energy released by the spring.

The power reserve: an important characteristic of automatic watches

The power reserve is an important parameter to take into account when discussing the operation of an automatic watch. This is the length of time the watch can continue to run without being worn or manually wound.

The power reserve capacity varies between automatic watch models, and mainly depends on the size and quality of the mainspring. Some watches have a power reserve of only 24 hours, while others can reach several days or even weeks.

The impact of your habits on the power reserve

Your daily habits have a direct impact on the power reserve of your automatic watch. If you are very active during the day, your watch will benefit from a constant supply of energy thanks to the movements of your wrist. On the other hand, if you are more sedentary or if you regularly take off your watch, the power reserve may run out more quickly.

It is therefore essential to adapt your habits according to the characteristics of your automatic watch, in order to make the most of its performance and preserve its lifespan.

Finally, don't forget that even if your automatic watch is recharged thanks to the movements of the wrist, it is sometimes necessary to wind it manually to maintain an optimal level of tension in the mainspring.