- A mechanical watch has one source of power - YOU! What powers you? Coffee perhaps? You may have just rolled out of bed, rubbed your eyes and felt the bedside table in fumbling motions for your luxury watch. You wind it without much thought, but in doing so, you have unleashed a series of remarkable movements that provide the power to your luxury watch.
In turning the knob, you wind the mainspring - the power source in mechanical watches. The mainspring is a spiral spring of metal ribbon coiled around an arbor (the central axle); the inner end of the mainspring is attached to the arbor with small hooks or tabs, and the outer end to the barrel ( a cylindrical box). The mainspring is wound by turning the arbor, but drives the watch movement by the barrel. This ensures that the watch is still being powered during winding. The arbor has a ratchet attached to it, with a click 
so that the force of the spring will not turn the arbor backwards, and thus unwinding it. Once the arbor is wound it no longer moves. The pull of the stored energy of the mainspring turns the barrel. The barrel has a ring of gear teeth around it. The ring of teeth interlocks with the center wheel pinion and drives the wheel train. In most watches the barrel rotates once every eight hours, thus the 40 hour spring needs five turns to fully unwind.Some useful facts pertaining to the mainspring of your Luxury Mechanical Watch.
- The Mainspring is wound around the arbor with great force. Disassembling the mainspring without the "know how" could cause the mainspring to suddenly release, causing injury. The mainspring should be 'let down' gently first by holding the winding knob and pulling the click back. This allows the spring to unwind slowly. In general ,the disassembling of any luxury watch, should be done by a watch professional.
- Older watches, such as those made before the 1960, had mainsprings that broke quite frequently. This was due to the constant stress cycles endured by the metal, causing the metal to weaken and then snap. The stress was the strongest directly around the arbor, where there was no space between the coils, this point could quite easily be reached, while winding. Although, metallurgy has improved, broken mainsprings although rare can occur.
- Some watches will no longer work when fully wound. This led to many theories of over winding. Over winding is a myth and does not validate the reason for fully wound watches to stop. Winding a watch all the way, does not damage the watch; however, over time the watch movements collect dust and the oil dries up. The dust and oil causes enough friction so the smooth running of the mainspring is hampered, leaving little force for the mainspring to turn until the end of its running period. If the owner continues to wind the watch, without servicing the watch, the friction reaches the flat part of the torque curve and the watch will stop, even though the watch is fully wound.
- Mainsprings can become tired or deformed, and lose some of there force. This will cause the running time between winding to be decreased. At this point your watch needs to be serviced, and your mainspring replaced if necessary.
Power reserve indicator: Some high end watches like the Audemars Piguet Arnold All Stars has an extra dial on the face indicating the amount of power left in the mainspring. Most dials interpret this into amount of remaining hours. A differential gear is crafted within this watch which determines how far the arbor has been turned compared to the barrel.
