Component record · Dial & hands
Motion Works
VerifiedThe collective name for the cannon pinion, minute wheel and hour wheel that together translate the going train's centre wheel rotation into correctly geared minute and hour hand display.
What it does
Provides the 12:1 hour-to-minute hand reduction and, via the cannon pinion's friction fit, allows the hands to be set without disturbing the running train.
How it works
Rotation from the centre wheel arbor (one revolution per hour) is picked up by the friction-fitted cannon pinion, geared down through the minute wheel to the hour wheel at a 12:1 ratio, so hour and minute hands stay correctly synchronised.
When the hands are set (via the keyless works and setting mechanism), the cannon pinion is turned directly and, because of its friction fit, slips relative to the centre wheel arbor rather than forcing the going train to turn, so setting the time does not run the train forwards or backwards.
Evolution
The three-part motion works arrangement has been the standard solution since the widespread adoption of independent hand-setting.
Known variations
- Standard 12-hour motion works
- Motion works incorporating calendar or additional indication trains in complicated watches
Identification for collectors
- Visible as the small stack of wheels on the dial side directly beneath the dial, once the dial is removed
Common failure modes
- Any of the constituent parts (cannon pinion, minute wheel, hour wheel) wearing or slipping
- Dial feet interference with motion works if misaligned during dial refitting
Photographs
Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.
Sources & references
- Daniels, G., Watchmaking
- de Carle, D., Practical Watch Repairing
Where sources disagree, the disagreement is stated rather than resolved silently.