Component record · Power
Crown Wheel (Winding Train)
VerifiedA small toothed wheel in the winding train that transmits turning force from the winding pinion to the ratchet wheel (not to be confused with the crown wheel of the verge escapement).
What it does
Passes the rotational force applied by the user at the crown through to the ratchet wheel, ultimately winding the mainspring.
How it works
In simple key-wound watches, a winding key engages the barrel arbor square directly or via a small train; in keyless watches, turning the crown drives a winding pinion that meshes with this crown wheel, which in turn drives the ratchet wheel and barrel arbor.
The term is a historical source of confusion: the same phrase, 'crown wheel', names both this winding-train part and the escape wheel of the verge (crown-wheel) escapement, an entirely different mechanism from an earlier era of watchmaking.
This crown wheel typically only engages during winding; during running, it plays no part in the going train and simply idles.
Evolution
Its layout changed considerably with the shift from key-winding to stem/keyless winding in the second half of the 19th century, but its basic function of relaying turning force to the ratchet wheel persisted.
Known variations
- Key-wind train crown wheel
- Keyless-work crown wheel driven by the winding pinion
Identification for collectors
- Found on the winding side of the barrel bridge; distinguish from the verge escapement's crown wheel by its position (winding train, not escapement) and by the presence of a stem or key square nearby
Common failure modes
- Worn teeth reducing winding efficiency
- Detachment from its arbor
Related photographs
No confidently matched photograph of this subject has been found yet. These photographs show a closely related record, and are not examples of the type described on this page.
Sources & references
- de Carle, D., Practical Watch Repairing
Where sources disagree, the disagreement is stated rather than resolved silently.