A mechanical watch has no battery. No circuit board. No quartz crystal oscillating at 32,768 Hz. It runs entirely on stored mechanical energy, released and regulated by a series of interlocking components that have been refined over centuries. Here's how it works.
The Mainspring: Stored Energy
The power source of a mechanical watch is the mainspring — a long, thin strip of metal coiled tightly inside a cylindrical container called the barrel. When wound (either by hand or by an automatic rotor), the mainspring stores potential energy in its coiled tension.
As the mainspring slowly uncoils, it releases that energy through the gear train. A fully wound mainspring in a typical watch might store enough energy to run for 40 to 80 hours, depending on the movement.
The Gear Train: Transmitting Power
The gear train is a series of interlocking wheels and pinions that transmit energy from the mainspring barrel to the escapement. Each wheel in the train turns at a different rate, stepping down the energy from the slow rotation of the barrel to the faster oscillation needed by the escapement.
The gear train also drives the hands. The center wheel typically completes one revolution per hour, driving the minute hand. Additional gearing drives the hour hand and, in watches with a seconds display, the seconds hand.
The Escapement: Controlled Release
The escapement is the mechanism that controls how quickly the mainspring's energy is released. Without it, the gear train would spin freely and the mainspring would uncoil in seconds.
The most common type is the lever escapement. It consists of an escape wheel (the last wheel in the gear train) and a pallet fork — a lever with two angled faces called pallets. As the balance wheel oscillates, it rocks the pallet fork back and forth, alternately locking and releasing the escape wheel one tooth at a time. This is the ticking sound of a mechanical watch.
The Balance Wheel: The Heartbeat
The balance wheel is the timekeeping element of the movement. It oscillates back and forth at a consistent frequency, controlled by a fine coiled spring called the hairspring (or balance spring). Each oscillation takes the same amount of time, dividing time into equal intervals.
Most modern mechanical movements beat at 6, 8, or 10 beats per second (21,600, 28,800, or 36,000 vibrations per hour). The 6498-pattern movement in the SR-01 beats at 18,000 vph — a slower, more traditional rate that is visible to the naked eye through the exhibition caseback.
Why It Matters
A mechanical watch is a self-contained mechanical computer — a device that measures time using nothing but carefully shaped metal parts, springs, and the laws of physics. It requires no external power source and can be serviced, repaired, and kept running indefinitely.
That's not a trivial thing. A well-made mechanical watch, properly maintained, can outlast its owner. The engineering behind it is centuries old and still works. That's worth appreciating.