The Complication
In the hierarchy of horological challenges, the management of torque is arguably more critical to chronometric performance than the neutralization of gravity. The constant force complication addresses a fundamental flaw in mechanical timekeeping: the non-linear discharge of energy from the mainspring. According to Hooke’s Law, the force exerted by a spring is proportional to its displacement. In a standard watch, the torque delivered to the escapement is highest when the watch is fully wound and diminishes as the spring uncoils. This fluctuation affects the amplitude of the balance wheel, leading to variations in rate—a phenomenon known as lack of isochronism.
Mechanically, constant force is typically achieved through two primary methods: the remontoire d’égalité and the fusée-and-chain. The remontoire is a secondary, smaller hairspring or blade spring positioned within the gear train, usually near the escapement. It is wound by the mainspring at regular intervals—typically every second or every fraction of a second—and then discharges a consistent, discrete amount of energy to the balance. This isolates the regulating organ from the variable torque of the main power source. In contrast, the fusée-and-chain utilizes a cone-shaped pulley (the fusée) connected to the mainspring barrel by a miniature steel chain. As the mainspring unwinds and its force weakens, the chain pulls on the wider part of the cone, increasing leverage and equalizing the torque output through mechanical advantage.
The execution of these systems requires extreme precision. In a remontoire system, the locking and unlocking mechanism must consume minimal energy while maintaining perfect timing. In a fusée-and-chain system, the chain itself—often consisting of over 500 individual links—must be robust enough to withstand the tension yet small enough to fit within the constraints of a 40mm to 45mm case. The result of a successfully implemented constant force mechanism is a flat torque curve, ensuring that the watch maintains the same rate of accuracy whether it has one hour or fifty hours of power reserve remaining.
History
The quest for constant force dates back to the 15th century, but its refinement is credited to the 16th-century clockmaker Jost Bürgi, who invented the remontoire to improve the accuracy of his astronomical clocks. However, the most significant historical milestone occurred in the 18th century during the race to solve the 'Longitude Problem.' John Harrison’s H4 marine chronometer, completed in 1759, utilized a remontoire to ensure that the motion of a ship would not interfere with the precision required for celestial navigation. Harrison’s success proved that constant force was the key to high-precision portable timekeeping.
In the 19th century, the complication was largely confined to high-precision deck watches and regulator clocks. It wasn't until the late 20th century that the mechanism was successfully miniaturized for the wristwatch. The modern era of constant force began in 1999 with François-Paul Journe’s Tourbillon Souverain. Journe was the first to incorporate a remontoire d’égalité into a production wristwatch tourbillon, setting a new standard for independent horology. Since then, the complication has moved from a niche historical curiosity to a benchmark of technical mastery for brands like A. Lange & Söhne and Girard-Perregaux.
Top makers in 2026
As of 2026, the market for constant force watches is dominated by a handful of manufactures that have mastered the integration of these systems into wearable, reliable movements. F.P. Journe remains the gold standard with the Tourbillon Souverain (Ref. TN). This piece utilizes a one-second remontoire that also provides a 'dead-beat' seconds function. Current secondary market prices for a 40mm platinum Ref. TN hover between $850,000 and $1,100,000 depending on dial configuration.
A. Lange & Söhne offers perhaps the most robust implementation in the Richard Lange Perpetual Calendar 'Terraluna' (Ref. 180.032). The L096.1 movement features a remontoire that ensures the massive energy required to jump the perpetual calendar displays does not disturb the balance’s amplitude. The retail price for the Terraluna in pink gold is approximately $230,000. For those seeking the fusée-and-chain approach, the Ferdinand Berthoud FB 1.3 is the definitive choice. This manufacture specializes in the fusée system, with the FB 1.3 in platinum retailing for roughly $260,000. Finally, IWC has pushed the complication into the 'sport-luxe' category with the Big Pilot’s Watch Constant-Force Tourbillon Edition 'IWC Racing' (Ref. IW590501), priced at $220,000, which integrates the constant force mechanism directly into the tourbillon cage.
Auction Records
The auction market for constant force pieces has seen exponential growth, particularly for early independent examples. At Phillips Geneva Watch Auction: XIV in November 2021, an F.P. Journe Tourbillon Souverain 'Souscription' No. 1—the very first of its kind—shattered records with a hammer price of CHF 3,539,000. This sale solidified the remontoire as a 'blue-chip' complication for collectors.
In May 2023, Christie’s Hong Kong sold a rare F.P. Journe Tourbillon Souverain with a jade dial for HKD 20,335,000 (approx. $2.6 million). Beyond Journe, Sotheby’s handled the sale of the George Daniels Anniversary watch in 2022, which features a remontoire system inspired by Daniels’ own 'Space Traveller' pocket watch. The piece achieved a hammer price of £2,300,000. These records indicate that while the complication is technical in nature, its value is driven by the provenance of the watchmaker and the rarity of the execution.
Buying Advice
Prospective buyers must approach the constant force complication with a high degree of technical scrutiny. First, verify the type of system. A remontoire is generally more reliable for daily wear but requires a watchmaker with specific training for service. A fusée-and-chain is visually spectacular but inherently more fragile; a sudden shock can cause the chain to snap or jump its tracks, which is a catastrophic failure requiring a full manufacture overhaul.
Common red flags include an inconsistent 'dead-beat' second hand (if the watch is so equipped), which suggests the remontoire is not locking correctly. Furthermore, check the power reserve indicator against the actual run time. If the watch stops significantly before the indicator reaches zero, the constant force spring may have lost its tension. Regarding acquisition, the 'grey market' offers significant discounts on brands like IWC or Girard-Perregaux (often 20-30% off MSRP), but for F.P. Journe or A. Lange & Söhne, the Authorized Dealer or Boutique remains the only way to ensure a valid warranty—a necessity for a complication of this complexity.
Alternatives in the Same Spend Range
If the $200,000 to $500,000 budget is available, but the constant force complication is not the primary goal, collectors often look toward Multi-Axis Tourbillons. The Greubel Forsey Double Tourbillon 30° offers a similar level of finishing and mechanical 'theater' but focuses on gravitational compensation rather than torque management.
Another alternative is the Resonance complication, most notably the Armin Strom Mirrored Force Resonance or the F.P. Journe Chronomètre à Résonance. Resonance achieves precision through the synchronization of two balance wheels, providing a different solution to the same problem of chronometric stability. Lastly, for those interested in high-frequency precision without the remontoire, the Zenith Defy Extreme Double Tourbillon provides a 1/100th of a second chronograph at a lower price point (approx. $70,000), though it lacks the artisanal prestige of a constant force movement.
Verdict
The constant force complication is the purist’s choice. It does not offer the visual flamboyance of a minute repeater or the utility of a perpetual calendar; instead, it represents an obsessive pursuit of chronometric integrity. For the collector who values the physics of timekeeping over the aesthetics of the dial, a remontoire or fusée-and-chain piece is an essential acquisition. It is a silent, invisible guardian of accuracy that remains one of the most difficult feats in modern watchmaking.