Glossary · Mechanism
Motion works
Display gearing that derives hour-hand motion from minute-hand motion, normally at a twelve-to-one reduction.
Explanation
The motion works transmit time indication rather than determine the oscillator's rate. In a conventional twelve-hour watch, the cannon pinion drives the minute wheel and its pinion drives the hour wheel. The hour hand therefore completes one turn while the minute hand completes twelve. This display ratio must not be confused with the ratios of the going train between the barrel and escapement.
Twenty-four-hour indications, indirect drives and unusual layouts require their own diagrams. Calendar mechanisms may take drive from the hour wheel or an associated intermediate part, but not every calendar shares one arrangement. A movement exterior often hides the motion works beneath the dial. Use a dial-side view or technical drawing when identifying the actual gears; an overall clock movement photograph is context, not a macro of the watch's hand-setting train.
Sources & references
- de Carle, D., Practical Watch Repairing — technical further reading; exact procedures require calibre documentation
- Reymondin et al., The Theory of Horology — construction and terminology further reading
Where sources disagree, the disagreement is stated rather than resolved silently.
What to record
- Record twelve- or twenty-four-hour indication.
- Locate the cannon pinion, minute wheel and hour wheel in exact documentation.
- Distinguish display gearing from the going train.
Do not remove hands or dial merely to trace gearing; fragile printing and luminous material may be disturbed.