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The Encyclopedia of Horology

England (early development); refined across Europe · Documented in Harrison's work from the 1730s–1750s; refined through the 18th and 19th centuries for precision regulators and chronometers

Remontoire (Constant-Force) Mechanism

Historical attribution

A constant-force solution that addresses the same underlying problem as the fusee (a mainspring's declining torque) by a different mechanical route, and a mechanism still revived in some modern high-complication wristwatches.

A remontoire periodically rewinds a small secondary spring or weight that itself drives the escapement, isolating the escapement from the directly varying force of the mainspring or main weight and delivering a much more uniform driving force over each rewind interval.

Harrison's sea clocks used a form of remontoire as part of achieving the consistency needed for longitude-grade timekeeping; later precision regulator and chronometer makers developed further variants, including spring-remontoire forms used in some fine watches.

How to verify this yourself

As a mechanism refined incrementally by many makers without one uncontested founding patent, verify specific claims against Harrison's own surviving papers (Royal Museums Greenwich) and subsequent clock-history literature rather than assuming a single inventor or filing.

Manufacturers known to have used it

  • John Harrison (sea clocks)
  • later precision regulator makers
  • some modern haute horlogerie manufacturers using remontoire wristwatch calibres

Related photographs

Replica of John Harrison's first marine timekeeper, by Herbert Davies, Emsworth, Hampshire, completed c. 1962 - Clockmakers' Museum - London, UK - DSC05428
Replica of John Harrison's first marine timekeeper, by Herbert Davies, Emsworth, Hampshire, completed c. 1962 - Clockmakers' Museum - London, UK - DSC05428 — Daderot, CC0. Wikimedia Commons file page

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

  1. Royal Museums Greenwich, catalogue and gallery notes on Harrison's timekeepers
  2. Antiquarian Horological Society, articles on remontoire mechanisms

Where sources disagree, the disagreement is stated rather than resolved silently.