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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.

Background

A remontoire isolates the escapement from the variable forces of the mainspring or wheel train, so that only the constant force of the remontoire reaches the timekeeping components. Frequent rewinding cycles help to average out any potential variations in the clock's rate, making the mechanism a vital component for high-precision timekeeping. The gravity remontoire is attributed to Swiss clockmaker Jost Bürgi around 1595, while the spring remontoire was later developed by John Harrison for his marine chronometers. Thomas Mudge also contributed to the development of the mechanism, suggesting that the force derived from the mainspring should be equalized by using it to wind another smaller spring.

Written from the encyclopedia entries listed under Sources; each statement was checked against the cited text.

How it works

  • Remontoires are classified as either gravity, spring, or electric types based on the source of their power.
  • The mechanism can be integrated directly into the escapement or located at a wheel in the train upstream from the escapement.
  • Spring remontoires are the only type suitable for use in watches because weight-based mechanisms would be disrupted by the movement of a wearer's wrist.

Later history

  • Derek Pratt famously utilized remontoire mechanisms in his work, including an integration inside a tourbillon carriage completed in 1982.

Where sources differ

  • Date. This record gives: “Documented in Harrison's work from the 1730s–1750s”. The cited history describes an earlier gravity remontoire by Jost Bürgi around 1595, before Harrison's work.

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

Photographs

EB1911 - Clock - Fig. 15.—Gravity Train Remontoire
EB1911 - Clock - Fig. 15.—Gravity Train Remontoire — AnonymousUnknown author, Public domain. Wikimedia Commons file page
EB1911 - Clock - Fig. 16.—Spring Remontoire
EB1911 - Clock - Fig. 16.—Spring Remontoire — AnonymousUnknown author, Public domain. Wikimedia Commons file page
EB1911 - Clock - Fig. 21.—Chronometer Spring Remontoire
EB1911 - Clock - Fig. 21.—Chronometer Spring Remontoire — AnonymousUnknown author, Public domain. Wikimedia Commons file page
EB1911 - Clock - Fig. 32.—Hope Jones Electrical Remontoire
EB1911 - Clock - Fig. 32.—Hope Jones Electrical Remontoire — AnonymousUnknown author, Public domain. Wikimedia Commons file page

Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.

Sources & references

  1. Remontoire, Wikipedia (English), retrieved 2026-10-28 (text CC BY-SA 4.0)
  2. Royal Museums Greenwich, catalogue and gallery notes on Harrison's timekeepers
  3. Antiquarian Horological Society, articles on remontoire mechanisms

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