Mechanical Watches and Power Reserve
Mechanical watches do not need electric power
Mechanical wristwatches are driven by a winding spring in the movement. This spring can be charged both by movement in automatic watches and by turning the crown in hand-wound watches. The energy stored in this way moves the hands on the dial via the cog wheels.
In automatic watches, a so-called rotor on the watch's bottom winds the movement. This can rotate freely and has a weight on one side so that it swings back and forth with the movement on the wrist and winds the spring. Regular wearing of the watch constantly keeps the mainspring wound and ensures that the movement is constantly driven.
In hand-wound watches, the spring is tensioned by turning the crown. This is also possible with automatic watches, but not necessary.
The so-called power reserve of a watch determines how long the mainspring can drive the movement without winding. High-quality mechanical Junkers watches store up to 40 hours, i.e. have a power reserve of almost two days.