Unlike a quartz watch, an automatic watch is purely mechanical. This means: there is no battery. the energy that makes the watch run is generated by winding the mainspring with a crown or rotor. The automatic watch developed relatively late – until a few decades ago, hand-wound wristwatches were the absolute standard.
In a hand-wound watch, the spring that continuously delivers energy to the movement is tensioned via the crown. this invention by abraham louis breguet completely revolutionized the world of pocket watches back then! For the first time, no separate key was needed to wind the movement. Virtually all modern automatic watches have an optional manual winding mechanism.
The energy of the mainspring is transferred to the wheel and hand movement, causing the hands to turn. So that not all the energy is released at once, it needs the escapement – the frequency of which is regulated by the balance wheel. But how exactly does an automatic watch work? This article shows the function of a mechanical watch in detail.
Winding a mechanical watch
First of all, the spring can be tensioned by means of the manual winding mechanism. For this purpose, the crown of the watch is simply placed in the winding position and turned clockwise. Via the winding stem, the force reaches the spring barrel, where the spring is tensioned. Above it lies the ratchet wheel, in which a so-called ratchet pawl hooks in. This prevents the spring from relaxing and releasing its energy directly again.
With an automatic watch, the whole thing doesn’t look much different – except that the manual winding mechanism is replaced by a rotor. When it rotates, the gear wheel underneath it pulls the winding wheel and thus gives the power back to the mainspring barrel. Because there is much less power available than with manual winding, the rotor must rotate much more frequently than the crown when winding by hand.
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The clocking of the watch by the balance wheel
Normally, the mainspring would quickly relax again and the hands would suddenly turn x times. To prevent this from happening, the power output from the mainspring is regulated. This is done with the help of the balance wheel. The balance is the real "heart" of a mechanical watch movement. this component oscillates back and forth, limiting the energy output from the spring to normal time.
The gear train conducts the energy from the mainspring to the balance wheel. The so-called escapement (usually an escape wheel escapement on modern watches) then determines how much power is transmitted to the gear train via the mainspring. On the top of the wheel movement, the hands are fixed – depending on how fast they rotate, this is the second, minute, or even the hour hand.
The balance oscillates at a certain frequency. This is usually around 3 hertz (21.600 half oscillations per hour) or at 4 hertz (28.800 half oscillations per hour). When the balance wheel rotates in one direction, the escape wheel gives up some space and the energy can be transferred from the spring to the gears. Then the balance oscillates in the other direction and releases the same amount of energy in a controlled way. This results in the creeping second hand on a mechanical watch.
Complications make things complicated
the name complication for the functions of a watch does not come by chance: each additional function provides for a considerable additional effort in the construction of the movement. no matter if GMT function, moon phase or chronograph: everything is realized with the help of additional gears in the movement. The simplest form is a classic mechanical movement with manual winding.