Oh I didn't know this! Is this only for HMT automatic watches? Because I thought the regular automatic watches have a spring that gains energy due to the movement of the wrist and thus operates. Once the movement stops, the watch stops later.
This is the way it works:
1.
Automatic Winding: There is a heavy rotor inside the watch, which has an awkward center of gravity, so any movement will spin it. This winds the mainspring (coil), which is slowly loosened and controlled by the balance wheel/escapement combination, else it will immediately loose all tension; ie energy.
2.
Manual Winding: Same as above, but there is NO rotor, and the crown is twisted to tighten the mainspring as above. (The Pilot is like this). That is why these watches are the thinnest possible, since the rotor is not accommodated and just the movement for the drive to tighten the mainspring.
3.
Some automatics can have the option of (2). So one can use the rotor (hand movement) or tighten the mainspring using the crown. The Pilot, does not offer this.
4. All the above are known as
mechanical watches.
5.
Kinetic (Seiko): A rotor spins and charges a high storage battery. So this is not a mechanical, but actually a hybrid between quartz and mechanical.
6.
Quartz: A battery is used to power a crystal which oscillates and maintains time, and in turn the gear train. Eco-Drive and Solar watches would fall under this too.