01 / Movement
Mainspring
A coiled spring that stores energy in a mechanical watch.
- Where it sits
- Inside the movement’s barrel.
- What it does
- Releases stored energy to drive the wheel train as it unwinds.
- Common variations
- Different spring and barrel arrangements support different movement designs.
- What to notice
- A stated power reserve describes running duration; it does not by itself describe accuracy.
02 / Movement
Escapement
The mechanism that meters the release of energy through the wheel train.
- Where it sits
- Between the wheel train and the balance assembly.
- What it does
- Works with the oscillator to control the train’s advance and replenish the balance’s motion.
- Common variations
- The Swiss lever is one design; other escapement architectures also exist.
- What to notice
- In a visible movement, look for the small interacting components beside the balance.
03 / Movement
Balance & hairspring
The oscillating assembly that provides a mechanical watch’s rhythm.
- Where it sits
- Within the movement, supported by a balance cock or bridge.
- What it does
- The balance swings back and forth while the hairspring supplies the restoring force.
- Common variations
- Different balance, spring and regulation systems.
- What to notice
- Look for the rapidly oscillating wheel rather than the slower winding rotor.
04 / Movement
Rotor
An oscillating weight used in an automatic winding mechanism.
- Where it sits
- Often visible over the movement through a display caseback.
- What it does
- Converts motion from wearing the watch into winding energy.
- Common variations
- Central rotors, micro-rotors and peripheral arrangements.
- What to notice
- A rotor indicates automatic winding; its absence from view alone does not identify the movement type.
05 / Movement
Gear train
A series of meshing wheels and pinions that transmits motion.
- Where it sits
- Inside the movement, beneath its bridges and plates.
- What it does
- In a mechanical watch, the going train carries energy from the barrel towards the escapement.
- Common variations
- Wheel layouts and gear ratios depend on the movement design.
- What to notice
- The train works with the escapement and oscillator; the gears alone do not establish the timekeeping rhythm.
