The constant-force mechanism based on fusee and chain is a rare type of horological artifact, the very existence of which in modern watchmaking evokes as much raised eyebrows as pure admiration. Next to some of its modern peers featuring silicone parts or hi-tech springs the fusee-and-chain may seem like a horse carriage in the middle of a 10-lane highway. Yet, its aesthetic appeal and almost weird antique charisma are extremely compelling.

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The chain-and-fusee of Chronométrie Ferdinand Berthoud FB1

What’s the chain-and-fusee mechanism?

While the chain-and-fusee constant force mechanism does remain extremely rare in modern watchmaking, from time to time some top brands dare to equip their flagship-level pieces with it. At the very core, this mechanical oddity is meant to improve the precision, just like any constant force mechanism. But if in most similar cases, we are talking high-tech developments, the latest patents or at least a fancy design or exotic materials, this principle of equalizing the given power to the balance wheel has not changed much for several hundred years. And of course going such a complex route instead of regular tuning your balance and escapement is more about a poetic touch rather than necessity. As we all know there’s ton of chronometer-certified watches around with far more simple regulation systems.
Romain Gauthier Logical One

Chain reaction: How does it work?

The mechanism has got its name from the French word fusée – yarn on the spindle. Due to the conical part with a special groove on which a chain or a string is attached, the design slightly resembles a weaving loom. It is widely considered that Leonardo da Vinci was the first, or at least one of the first engineers, to adapt this principle to horology needs. Unlike pendulums, delivering the same amount of energy to the wheel train regardless of the winding rate, the mainspring of a pocket watch or a wristwatch provides different amounts of energy on maximum and minimum tensions, no matter how perfect is your oscillator – and don’t forget, the chain-and-fusee came to use in times when the timekeeping was far from perfect. A chain or a string connected to the winding barrel is wound on a cone of ever-decreasing rings. As a result, the fusee resists the spring stronger during full tension and easier during its last working hours. Thus, neutralizing the possible error.
Zenith Academy Georges Favre-Jacot

Purpose or aesthetics?

Obviously the mass production of such mechanism has never been in question. The required level of skill, the amount of manual work, and the final cost automatically narrowed the range of its happy owners. Add here the miniaturization issues, and  you’ve basically got the picture of why nowadays only top watchmakers dare to experiment with the fusee in wristwatches. The delicate nature of any top-tier complication is another issue. While there’s definitely some extra collectable value involved, the seasoned connoisseurs – and you don’t end up with such a piece accidentally – might be too cautious for messing with such a whimsical antique technologies. When a thin metal chain that can easily be pulled through a needle’s eye is attached to continuously moving objects, you don’t get the most durable element in modern watchmaking, right?
Breguet Tradition 7047
However, the research in the field of reliability doesn’t stand still. Several years ago the independent Swiss brand Romain Gauthier came up with the Logical One watch featuring the patented chain mixing the metal elements with the artificial rubies. It minimizes friction and potential wear, and does not require lubricants at all. And the best part – being perfectly visible right from the dial side it’s a real feast for the eyes.
Chronométrie Ferdinand Berthoud FB1

The chain-and-fusee renaissance

We’ve previously mentioned the rarity of chain-and-fusee constant-force mechanism in the modern market. Well, bearing in mind it was nearly absent for the whole XX century, the today’s status quo still feels quite a comeback. The recent Chronométrie Ferdinand Berthoud Carburised Steel Regulator victory in Chronometry category of Grand Prix d'horlogerie de Genève following the Chronométrie Ferdinand Berthoud FB1 taking the Grand Prix in 2016 proves that this technology is still too early to be dismissed. The movement of the still produced FB1 consists of 1120 parts, 790 of which comprise the fusee and the 28-cm chain. How can anyone not love something that thought-out! For the greater effect, the guys at Ferdinand Berthoud even managed to fix the whole construction to the mainplate from one side only, like a flying tourbillon. 
Cabestan Winch Tourbillon Vertical
The mighty Zenith Academy Georges Favre-Jacot, released several years ago in celebration of the brand’s 150th anniversary also proudly shows the fusee directly on the dial side, crowning it with two nicely decorated bridges. Another stunning example utilizing the classical aesthetics is Breguet Tradition 7047 with its asymmetrical open-worked dial. But rich tradition does not limit the chain-and-fusee within the dressy niche. The creative watch rebels can use it too, and the Cabestan Winch Tourbillon Vertical perfectly illustrates it. The aggressive ultra-modern design has no hands at all, the moving disks display time and power reserve. Yet, there’s a place for the familiar cone connected with a chain. In such an environment, the old system looks nothing like a grandpa's heirloom, but rather a gadget from a fantastic future.
The chain of the Romain Gauthier Logical One