Step 4 of 7
Mechanical watch step 4 of 7: The gear train
The mainspring’s force runs through the gears: from the barrel to the centre wheel (once an hour, carrying the minute hand), the third wheel, the fourth wheel (once a minute, carrying the seconds hand) and on to the escape wheel, where the balance lets it out a tick at a time.
Tools: none, just your hands
All 7 steps
What is in it
- Mainspring in its barrel · stores the energy
- Gear train · centre, third and fourth wheels
- Escapement · escape wheel and pallet fork
- Balance wheel and hairspring · the timekeeper
- Winding and setting works · crown, stem, pinions, click
- Motion works, dial and hands · on the dial side
- 21 jewels · synthetic rubies the pivots turn in
Questions
How does a mechanical watch work without a battery?
A coiled mainspring stores the energy you put in by winding. A train of gears carries its force to the escapement, which lets it out a tick at a time, and the balance wheel on its hairspring sets the pace.
What does 28,800 beats per hour mean?
The escapement ticks 8 times a second: the balance swings back and forth 4 times a second. Many watches beat at 21,600 an hour, 6 ticks a second.
What are the jewels in a watch for?
They are synthetic rubies that the pivots of the wheels turn in: hard and smooth, so the pivots wear less and turn with less friction.
How many times should I turn the crown?
Until it stops: typically 20 to 40 turns from empty, depending on the movement. Once a day keeps a hand-wound watch running.
What is the power reserve?
How long the watch runs on a full wind: 40 hours here. A day later it still has 16 hours left.
Safety
Opening a watch exposes its movement to dust and moisture, and its parts are tiny: leave servicing to a watchmaker.
About this guide
The watch here is of our own design, a typical hand-wound movement with small seconds: 28,800 beats an hour (4 swings of the balance a second, 8 ticks), a 15-tooth escape wheel, 21 jewels and 40 hours of power reserve. Its gearing follows from those numbers: the fourth wheel turns once a minute, the escape wheel 16 times a minute, the centre wheel once an hour.
Real watches differ: many beat 21,600 times an hour, and fully winding one takes from about 20 to 40 turns of the crown. The day-long speed-up is 21,600 times: 86,400 seconds in four.
Sources: Farer: how to wind a mechanical watch, Shinola: winding guide (about 30 turns for a 42-hour reserve).
The 3D models, drawings and text are our own.