There is no contemporary watchmaker more deeply connected to and profoundly associated with the remontoir d’egalite than François-Paul Journe. Amazingly, his interest in this mechanism started in the early 80s, when he was challenged by the famous watch collector Dr. Eugen Gschwind to create a Tourbillon pocket watch with a remontoir d’égalite to combat against Journe’s friend and mentor, George Daniels. Daniels had created a pocket watch, which featured a 15-second remontoir that was rearmed four times a minute by the cage itself. It was an achievement that Daniels felt no one else could equal. When he found out that a young Parisian watchmaker had created something of equal merit, and that the solution for the remontoir d’égalite might, in fact, be even more elegant, he was, of course, both irritated and intrigued. From there, Journe, the young watchmaker in question, went on to create the very first wristwatch, combining a tourbillon and remontoir d’égalite with his legendary 11/91 timepiece. Before introducing this watch as a subscription piece in 1999, two more prototypes were made — one recently sold at auction for the staggering price of CHF 7,320,000, was numbered, 15/93. The other watch 16/93 is potentially going to go on auction next year.

François-Paul Journe honouring his mentor George Daniels with a special Chronomètre Souverain during an intimate dinner organized by John and William Asprey in 2010

Today, Journe features his legendary remontoir d’égalite featuring his flat, bladed spring on a variety of watches, including his Tourbillon Souverain Vertical, his new version of the resonance as well as on his Chronomètre Optimum, the latter combining it with a version of Breguet’s natural escapement. Yet for many years, the remontoir d’égalite has remained largely overlooked as a complication.

F.P. Journe Tourbillon Souverain Vertical

With the unveiling of the revitalized Urban Jürgensen’s extraordinary UJ‑1, which introduces Derek Pratt’s tourbillon with a cage‑mounted Reuleaux triangle remontoir to a serially produced wristwatch, it seems that the remontoir is finally about to have its day in the sun. For many years, despite being far more historically significant and playing a crucial role in the creation of John Harrison’s H4, the first successful marine chronometer that eventually enabled man’s conquest of the oceans, the remontoir has remained largely overlooked, especially when compared to the far more celebrated regulating device like the tourbillon.

The magnificent Urban Jürgensen UJ-1 recreates Derek Pratt’s Oval pocket watch with his signature tourbillon and cage-mounted remontoir for the wrist

Says watchmaker Bart Grönefeld, “Part of this is that the remontoir is harder to understand. With a tourbillon, you can see the cage turning and you get it — there’s this big device averaging errors caused by gravity. But with the remontoir, you’re talking about something small and often hidden from your eyes, unless you really know where to look. That’s why when my brother Tim and I wanted to create the Grönefeld [1941] eight‑second remontoir, we engineered the remontoir system to be as visible as possible, so that people would understand that there was something very special going on in their watch.”

Grönefeld 1941 Remontoire

But what exactly is going on? To draw a comparison with Greek mythology, Thetis, mother of the great Achilles, dips him in the River Styx, making him invulnerable in all places save the heel that she held him by. The term “Achilles’ heel” thus became a way of pointing out a weakness in a person or system that might otherwise seem all powerful. For those of you familiar with Star Wars lore, Luke Skywalker flies his X‑wing down into the Death Star’s trench and uses the Force to send torpedoes down an exhaust port and into the otherwise invulnerable genocide machine’s reactor core, causing it to explode into smithereens. We later learn that this Achilles’ heel was placed there intentionally by Galen Erso, the Death Star’s primary engineer and a secret Rebel sympathizer, so that it could later be destroyed.

Thetis immersing her son, Achilles, in the River Styx by Antoine Borel, 18th century; in the collection of the Galleria Nazionale, Parma, Italy (Image: Britannica)

In the Battle of Yavin, Luke Skywalker dives into the trenches of the Death Star in his X-Wing before he fires a torpedo towards an exhaust port that would destroy the station — an intentional flaw in the design sabotaged by scientist Galen Erso

Since time immemorial, the primary Achilles’ heel of the mechanical watch has been its power source, known as the mainspring. This is, as the name implies, a massive spring that is coiled up and contained inside what we call the barrel. Winding the barrel tightens the mainspring, allowing it to store potential energy, which is released as it unwinds and the barrel turns. When that happens, it sends energy down the gear train by engaging the pinion of the second, or center wheel, which then engages the pinion of the third wheel, which is similarly geared to the fourth wheel. The fourth wheel completes one rotation every 60 seconds and, as such, is also called the seconds wheel. In a direct drive seconds indicator, the seconds hand is fixed to this wheel. The seconds wheel drives the escape wheel, which sends pulses of energy to the escapement each time it unlocks. Finally, the escapement directs the energy, which comes all the way from the mainspring, to the balance wheel.

As an amusing aside, I asked the disruptive A.I. application DeepSeek to describe the gear train in the voice of an urban teenager. It came up with the following: “These gears are like the squad passing the ball down the court, transferring that energy step by step.” Not totally inaccurate, I have to say.

In a mechanical movement, the torque delivered by the mainspring decreases as it unwinds. This affects the amplitude of the balance wheel, and in turn, the rate of the watch

As you can see, this is a long journey for that energy and it can be lost to various frictions and inefficiencies, such as the imprecise meshing of gear teeth or friction created by pivots. But the problem is that the energy when the barrel is fully wound and when it is close to being fully unwound is sub‑optimum.

The common belief is that the first 20 percent and last 20 percent of power reserve is not ideal, and that the torque sent down the gear train is either too strong or too weak, causing the balance wheel to lose isochronism, leading to inaccuracy in the watch. The reason the power reserve indicator was created and why it is so instrumental in timepieces such as the marine chronometer was not just to provide a reading of energy left in your watch, but also that in the case of a precision device, we would know ideally the sweet spot to keep energy levels at.

Why The Remontoir?

Over watchmaking’s history, several mechanisms have been invented to improve accuracy. One such device is the tourbillon, originally patented by the legendary Abraham‑Louis Breguet to correct for gravity’s erosive effect on the regulating organ, when pocket watches were placed in the vertical position. Yet, while gazing into the microcosm that is Breguet’s whirlwind is a seductive act of micro‑mechanical wonder, it wasn’t the most important contribution to improving accuracy. The application of the tourbillon is actually very limited and only helps watches kept for long periods in the vertical position. In the most accurate timekeepers, such as marine chronometers used by navies to determine longitude at sea, you never see a tourbillon.

The remontoire in John Harrison’s H4 is quite complex. It consists of a detent with 5 arms, a heart cam, a flywheel, a remontoire spring housed in a carrier mounted on the fourth wheel, and a stop wheel with pins located on the hub of the carrier/contrate wheel (Image: Redfern Animation, www.redfernanimation.com)

Instead, taking pride of place in these precision instruments is the remontoir d’égalité, a constant force mechanism that was such a massive contribution to accuracy in modern watches that it allowed mankind to safely navigate the oceans. The result of this was the colonization of much of the known world by European nations that waged war against indigenous people armed with, in the words of Rowan Atkinson’s Blackadder, “sharpened fruit.” For the purpose of this article, we will put aside the residual controversy related to this, so that we might revel at the age of timekeeping accuracy brought on by this invention, and have a better understanding of the historical precedent and global cultural context of its creation.

Most importantly, we will look at the modern brands and watchmakers that have implemented different types of constant force or remontoir d’égalité devices in their wristwatches. You might ask, what is the point of creating a tiny mechanical device that allows these watches to lift their performance gains so significantly, in an era where the most accurate and expensive mechanical watch will never be as accurate as the cheapest electronic device? I would reply it is because the former is an innately human endeavor. We humans are somehow encoded to have a certain sense of awe and wonder for micro‑mechanics. It is for this reason we cannot help but revel at Leonardo da Vinci’s technical drawings, or smile at Jules Verne’s steampunk dread machines. I would posit that the remontoir d’égalité is one of the highest expressions of our human ingenuity.

The Art of Consistency

Now there have been many different solutions to optimize the power coming from the mainspring. One is the fusée and chain. Here, the barrel is connected to a cone‑shaped pulley called a fusée that gradually increases in diameter from one end to the other. The barrel and the fusée are connected by a tiny chain, which is truly a work of micro‑ mechanical artistry of the highest order. As the mainspring unwinds, the chain moves along the helical grooves on the fusée, which guide it from the narrow end to the wide end, changing the effective radius at which force from the mainspring is transmitted. When the mainspring is fully wound and strongest, the chain pulls at the narrowest part of the fusée, providing less mechanical advantage. As the spring weakens, the chain moves to the widest part, increasing leverage. This compensates for the dropping torque and creates a more stable and even power supply.

A traditional fusée and chain consists of a chain with one end connected to the barrel and the other to the fusée, which is a cone that sits on the centre wheel arbor

The first modern timepiece to feature a fusée‑and‑chain mechanism was the A. Lange & Söhne Tourbillon “Pour le Mérite.” In the context of 1994, when this watch was unveiled, it was simply mind‑blowing. Günter Blümlein, the genius behind the brand’s revival, had created a timepiece that miniaturized this mechanism to the size that it could fit in a 38.5mm wristwatch.

A. Lange & Söhne Tourbillon “Pour le Mérite”. As you can see, there are planetary gears on the fusée which serve to maintain power during winding. This is essential in a fusée system, as the fusée rotates in one direction while winding and in the opposite direction during operation, interrupting power flow unless compensated by a differential

Since then the fusée and chain has made its way into the Breguet Tradition Tourbillon, Zenith Academy Georges Favre‑Jacot, the Cabestan vertical tourbillon, and, most recently, in the stunning Ferdinand Berthoud FB RES and FB3 watches.

One very inventive watch featuring a modified version of the fusée and chain is Romain Gauthier’s Logical One that replaces the cone‑shaped fusée mechanism with a snail cam, and uses very cool ruby rollers combined with steel links for the chain. This entire mechanism is arrayed to the left of the Logical One, with the single barrel at the back of the watch fitted with sapphire crystal covers to reduce friction and add visual dynamics. I’ve always found it funny that this timepiece features a power reserve indicator in the back next to the barrel, because one look at the inside of its transparent cover would let you know the state of wind. Winding is achieved with a pusher integrated into the side of the case, which, it must be said, is genuinely fun to use.

The fusée in the Logical One is not a conventional cone but a flat snail cam. This ingenious solution translates the three-dimensional, tapering profile of a classic fusée into a two-dimensional form that preserves the same functional properties. This allows the chain to transmit force in a perfectly straight line, eliminating offset angles and significantly reducing stress on the chain links

Another relatively straightforward mechanism is the Maltese cross stopwork, which limits the turning of the barrel and, correspondingly, the tension of the mainspring. The idea behind this is to only use the ideal part of the power supply. But both of these solutions are attempts to “fix” the variable power coming from the barrel. (Also note that both of these can and have been used together with remontoirs. A good example is the aforementioned Harrison’s H4, the world’s first marine chronometer that combines a fusée‑and‑ chain device with a seven‑and‑a‑half second remontoir d’égalité. But more on that later.)

The stopwork limits how much the chain wraps around the fusée at full wind and also prevents the mainspring from being wound too tightly. By restricting the operational range of the mainspring to its most consistent torque zone, the stopwork helps ensure stable energy delivery throughout the power reserve.

The remontoir d’égalité, on the other hand, removes the balance wheel altogether from the influence of the barrel. Indeed, the only use for the power coming from the barrel is to rewind the remontoir wheel, which in turn tensions the spring that actually delivers power to the balance wheel. That’s right — the remontoir that sits within the gear train is its own mighty autonomous energy source. It is an independent power supply that sits as close to the balance as possible and is the sole organism in the watch that delivers power to it.

This energy source is usually a coiled spring or a bladed spring that is rearmed on a regular interval — anywhere from each beat of the balance, as with Girard‑Perregaux’s Constant Escapement; to one second, as found in the new Urban Jürgensen UJ‑1 tourbillon with cage‑mounted remontoir, and François‑Paul Journe’s Tourbillon Souverain; to intervals of up to 10 seconds, such as in Bernhard Lederer’s Double Impulse Chronometer; to even an interval of every few minutes, such as the four‑minute remontoir found in Greubel Forsey’s Double Balancier.

The Caliber 1403 in F.P. Journe’s second-generation Tourbillon Souverain (TN) has a cut-out on the bridge that showcases the entire remontoire mechanism which relies on a blade spring

The remontoire in Bernhard Lederer’s Double Impulse Chronometer has undergone various refinements since his 2021 prototype. In the Central Impulse Chronometer 39mm shown here, it no longer relies on a Reuleaux triangle on the fourth wheel to control the release of the remontoire. Instead, a flywheel is now locked and unlocked every 10 seconds by a wheel with vertical pillars beneath the third wheel. This is to ensure the remaining train after the remontoire wheel is free from additional friction.

There is, of course, the theory that the longer the interval before a remontoir rewinds, the greater the chance that the delivery of power over that period might diminish slightly as the spring loses tension. While opinions on this may vary, there is still arguably a far greater consistency of power delivery over this much smaller time period, compared to a mechanism that relies directly on the mainspring.

There are, however, sticklers like my friend Bernhard Lederer, who insists that “a remontoir d’égalité is not the same as a constant force mechanism, because force delivered to the balance is not exactly constant.” To him, the only true constant force devices are the Constant Escapements created by the likes of Girard‑Perregaux and Ulysse Nardin that deliver the exact same energy with each impulse of the escapement to the balance wheel.

However, because for more than two decades the terms “constant force mechanism” and “remontoir d’égalité” have been used interchangeably, with apologies to Lederer, I’m going to use them in this way for this article. But I will distinguish Constant Escapements as a different type of system. An additional complication (pun intended) is the fact that there are also constant force mechanisms that rearm and discharge themselves multiple times a second, like the one created by Valérien Jaquet for Jacob & Co. for the Astronomia 4th Dimension.

Remontoirs that Shaped History

Before getting to the wristwatches that feature this amazing innovation, let’s look at the historical examples of this device.

The gravity remontoir was invented by Swiss mathematician, astronomer and clockmaker Jost Bürgi, long before the era of pendulum clocks. These were rewound using a massive weight that would fall a fixed distance over a period of time. Rewinding was thus generated using gravity. But these clocks had varying frictions and mechanical inefficiencies that made power delivery to the oscillator inconsistent. Bürgi’s invention was a second spring that delivered energy and that was also rewound at fixed intervals using gravity. Bürgi’s removal of the oscillator from the direct influence of the power supply would have a major influence on another individual who would introduce a spring remontoir to watchmaking and, in so doing, write one of the most significant chapters in both horological and human history: John Harrison.

Thomas King’s 1767 portrait of John Harrison, located at the Science and Society Picture Library, London

John Harrison’s prize-winning H4, the first true marine chronometer and one of the most important timekeepers ever made

The most famous constant force mechanism in watchmaking history, and the most groundbreaking implementation of a spring driven remontoir is found in John Harrison’s Marine Chronometer H4, with its 7.5‑second remontoir d’égalité. This is indisputably the most historically important use of constant force in human history? Why? Because it gave mankind the ability to finally calculate longitude at sea. Latitude, which is the measurement of how far north or south of the Equator you are, is straightforward and told by observing the height of the Sun at noon relative to the horizon. But determining longitude required something heretofore never achieved — a watch that was so accurate, it would deviate only a few seconds a year at maximum. This was required because the technique for calculating longitude consisted of determining your local time relative to time at a reference point, such as your port of departure.

The remontoir mechanism in John Harrison’s H4 (Image: Redfern Animation, www.redfernanimation.com)

Animated reconstruction of John Harrison’s remontoir mechanism as implemented in the H4 marine timekeeper. (Animation: Redfern Animation, www.redfernanimation.com)

The way it works is this: The Earth makes a full rotation of 360 degrees every 24 hours. Therefore, one hour of time difference equals 15 degrees of longitude. Four minutes of difference equals one degree of longitude. To show you how crucial timekeeping was at sea, that same four minutes’ time difference also equals 60 nautical miles at the Equator. But the challenge was to not only create the world’s most accurate clock or watch, but also one that would prove impervious to the temperature extremes, corrosion and the massive rolling and swaying of a ship on the ocean. There were other very cool elements present in the H4, including a modified verge escapement, diamond pallets, and yes, the previously discussed fusée and chain. But it was really a 7.5‑second spring driven remontoir d’égalité that was the game changer here that allowed Harrison to be the first to create a successful marine chronometer.

F.P. Journe Tourbillon Souverain, 1999

The first implementation of a remontoir d’égalité in a wristwatch produced in series was by François‑Paul Journe for his Tourbillon Souverain in 1999. Journe understood that a tourbillon was even more susceptible to the variation in torque coming from the mainspring. Why? Because it was significantly heavier than a normal escapement, balance wheel and spring. Power had to be recuperated by the escape wheel geared to rotating around a fixed fourth wheel and, especially in a tourbillon, it made sense to him.

François-Paul Journe

F.P. Journe Tourbillon Souverain, 1999

He was at the time shuttling between his uncle Michel’s restoration workshop in Paris, and the Musée des Art et Métiers. It was at the museum that he saw the clock with flat‑ bladed remontoir spring that would inspire his one‑second constant force device. Since the wheel that rewinds the spring jumps forward every second, he would eventually, and very logically, add a seconds hand attached to this wheel. No watchmaker of the modern era is more associated with the constant force mechanism than François‑Paul Journe. He has since implemented it in his 30‑second Vertical Tourbillon, the current version of his Chronomètre à Résonance and, in what is my favorite current production Journe watch, his Chronomètre Optimum, which combines his remontoir d’égalité with his modern interpretation of Breguet’s double‑wheeled natural escapement.

Chronomètre à Résonance with dual remontoirs

The remontoir mechanism in the F.P. Journe Vertical Tourbillon

His remontoir departs fundamentally from the more familiar coiled-spring designs. In the Tourbillon Souverain, the remontoir wheel serves to isolate the cage pinion from the direct torque of the mainspring, which would otherwise pass through the fourth wheel pinion. The remontoir wheel is carried on a pivoting lever that rotates around the axis of the cage pinion. One end of this lever engages with the remontoir spring, while the other is designed to lock against a stop wheel. As mainspring torque flows through the train, it causes the remontoir lever to pivot around the cage pinion. This counterclockwise motion deflects the remontoir spring, storing energy, until the opposite end of the lever locks into the stop wheel. At this point, the gear train is blocked and the escapement becomes fully decoupled from the mainspring.

Andreas Strehler Remontoir D’égalité, 2013

For those of you who don’t know Andreas Strehler, he is, behind the scenes, one of the most brilliant technical minds in watchmaking. Through his motto, “Engineer for the brands, watchmaker for the few,” he points out that although he is the technical brain behind a great number of creations in the industry, he is a watchmaker for the rare connoisseurs who recognize excellence and appreciate the mechanical artistry he brings to each piece. His ambition for his remontoir was to create a mechanism that operates independently of the balance wheel’s frequency. His remontoir, which first appeared in 2013, has become one of the most iconic versions of this complication. It is compact and sits on top of the seconds wheel. It is, if I may say so, a work of genius. He explains, “I was inspired by something I saw used in a chiming clock from the 1960s. Because power delivery was extremely variable, depending on whether the clock was chiming, they came up with a solution for a remontoir that operated with a satellite wheel. In their model, it was on the escapement. But I didn’t want to miniaturize the mechanism too much, because the tiny hairspring powering the remontoir would be very fragile.” Instead, Strehler’s remontoir directly powers the seconds wheel and is recharged every second. Here’s how it works.

Andreas Strehler Remontoir d’Égalité

The Strehler remontoir has a star‑ shaped satellite wheel. The points of this wheel rest against a stopping jewel mounted on a lever arm that is attached to the seconds wheel. The satellite wheel is mounted to a satellite arm that sits on the pinion of the seconds wheel, but it is connected through the gear train to the mainspring. Both the seconds wheel and the stopping arm with its jewel rotate smoothly.

Andreas Strehler

A remontoir spring connects the satellite arm and the stopping arm — this spring powers the seconds wheel, which is thus removed from the direct influence of the mainspring. Only the satellite wheel and arm are directly affected by the mainspring’s energy. However, because the stopping jewel blocks the satellite wheel and arm from advancing, they remain locked in place until the seconds wheel continues its rotation. As the seconds wheel turns, it moves the stopping jewel until it releases the satellite wheel, which then jumps forward.

Andreas Strehler debuted the remontoir in the Sauterelle in 2013. It is a highly compact setup in which all components of the remontoir are located on the fourth wheel, which ensures an undiluted energy transfer to the escapement

The satellite wheel turns because it is geared to a fixed track, rotating anticlockwise until it is caught again by the stopping jewel. This happens every time the stopping jewel rotates six degrees, which corresponds to six beats or exactly one second. As the satellite wheel moves, it rewinds the hairspring that drives the seconds wheel, providing consistent energy. And this drama of locking, releasing and rewinding repeats every second, creating one of the coolest micro‑mechanical theaters of interactive mechanism ever created. Smart, no?

IWC Constant Force Tourbillon

One of the most obvious yet often overlooked watches with a remontoir is the IWC Constant-Force Tourbillon, featuring a cage-mounted remontoir. The tourbillon with an integrated remontoir first appeared in the Portugieser Sidérale Scafusia in 2013 and has since found its way into several other models including the Big Pilot’s Watch Constant-Force Tourbillon.

IWC’s complex constant-force tourbillon with a matte black Ceratanium® case and the iconic Big Pilot’s Watch design

Notably, the patent observes that even within its brief cycle, a remontoir spring inevitably loses some tension as it unwinds, so the torque it supplies is not perfectly constant but instead tapers off slightly until it is rewound. This is a significant differentiating factor that sets it apart from other remontoirs.

In this design, the remontoir spring is mounted coaxially with the escape wheel inside the tourbillon cage, positioned between the escape wheel and a rotating tension ring that periodically rewinds it. The same shaft also carries a Reuleaux cam above the escape wheel. This cam drives an anchor, which controls a stop wheel mounted on a separate axis within the cage.

IWC Portugieser Constant-Force Tourbillon

The stop wheel engages a fixed tourbillon wheel on the main plate and periodically locks the rotation of the tourbillon cage. When the Reuleaux cam releases the anchor, the stop wheel unlocks, allowing the cage to rotate by a precise angle. This controlled rotation turns the tension ring, which rewinds the remontoir spring by the same amount each time. Meanwhile, the escape wheel itself is governed by a conventional lever connected to the balance wheel.

To counteract the slight drop in force as the remontoir spring unwinds, it adds a force-balancing mechanism mounted around the same escape wheel shaft. This consists of an eccentric, fixed off-center relative to the shaft, and a balance disk with two arms that rotates around the eccentric. The free end of the remontoir spring is attached to a mobile collet with a pin that presses on one arm of the disk, while the other end is attached to a fixed collet with another pin that bears on the opposite arm. As the spring unwinds and its tension drops, the eccentric layout causes the effective lever arms on the disk to change length, increasing mechanical advantage just enough to offset the loss of force. The result is that the torque transmitted to the escape wheel remains mathematically constant rather than merely approximate.

Greubel Forsey Double Balancier À Différentiel Constant, 2016

One of my favorite watches of all time is Greubel Forsey’s Double Balancier. From a visual perspective, the two inclined balance wheels, with rates averaged through a massive differential tower placed between them, represent one of the most stunning micro‑mechanical universes of all time. The way the differential works is: It has a central input wheel, which is the third wheel in the going train, and two output wheels at its top and bottom in a co-axial stack. Each output wheel transmits power down their respective gear trains. The roles of these wheels are fully interchangeable, enabling it to perform both torque splitting and rate averaging.  But even cooler is that sitting on top of the differential is a spring remontoir that controls the quality of power being delivered to these two output paths and that is rearmed or rewound every four minutes. The top of the remontoir mechanism above the differential tower is a unique four‑ minute rotation indicator that shows the periodic rewinding of the remontoir, giving a visual cue to the complexity of the mechanism in action.

The differential has a coaxial construction, with the input wheel (third wheel)  positioned centrally between two output wheels – one above and one below in the stack.

Each output wheel (there are 2 outputs) in the differential has a spring pinned to its spokes, which provides constant tension to the rest of the wheel train

Arnold & Son Constant Force Tourbillon, 2016 and 2025

The finishing and execution of the Arnold & Son Constant Force Tourbillon can be best described as “high‑quality industrial,” featuring no sharp inner angles but showcasing well‑executed machine beveling for its skeletonized movement. Yet the underlying technical construction of the watch remains very impressive.

The caliber A&S5119 in the original Arnold & Son Constant Force Tourbillon launched in 2016

The Arnold & Son Constant Force Tourbillon 11 launched this year recreates the movement architecture of the Breguet No. 169

The movement is fully skeletonized and powered by two barrels. Power flows through the gear train to the remontoir d’égalité, which sits on top of the watch’s seconds wheel. This remontoir operates similarly to the Andreas Strehler design. It features a satellite gear mounted on a rotating planet carrier, which is co‑axial with the output seconds wheel. The satellite includes a star‑shaped locking wheel that is periodically blocked by a stop finger. This stop finger is fixed relative to the output wheel, which is driven by the remontoir spring. As the spring unwinds, it powers the output wheel and escapement, and the stop finger rotates with it. The escapement beats at 21,600 vibrations per hour, or six beats per second, meaning that every sixth beat — exactly once per second — the stop finger advances just enough to release a tooth of the star wheel.

When this happens, the planet carrier is briefly allowed to rotate under mainspring torque. Since the satellite is engaged with a fixed wheel, it is forced to rotate on its axis as the carrier advances, and this motion rewinds the remontoir spring. The satellite is quickly locked again by the next tooth engaging the stop finger. Because the output is driven solely by the remontoir spring and the carrier advances at regular one‑second intervals, the mechanism produces a true deadbeat seconds display, with the carrier making one visible jump per second, independent of torque fluctuations from the mainspring.

How is this connected to the smoothly rotating tourbillon next to the one‑second remontoir? Well, the output wheel of the remontoir mechanism is geared to an intermediate wheel, which in turn drives the toothed perimeter of the tourbillon cage, causing it to rotate. The dynamic interplay between the remontoir‑driven deadbeat seconds mechanism on the left and the smoothly rotating tourbillon on the right creates a captivating contrast.

My only criticism of this watch is that at 46mm wide, it’s rather big in the context of today’s prevailing taste for classic sized watches. And for its near USD 200,000 price tag, the finishing of the inner angles of all four bridges on the front and the back of the watch could be more spectacular. But it is, nonetheless, a visual powerhouse.

This year Arnold & Son introduced the Constant Force Tourbillon 11 which recreates the movement architecture of the Breguet No. 169. After John Arnold’s death in 1799, his close friend and fellow watchmaker, Abraham‑Louis Breguet, paid tribute by incorporating his newly developed tourbillon mechanism into Arnold’s marine chronometer No. 11. This modified timepiece became known as Breguet No. 169. The Constant Force Tourbillon 11 is an incredibly beautiful timepiece with the remontoir mechanism driving a dead seconds indication in an aperture at 4 o’clock on an enamel dial. While the movement architecture, with the tourbillon located on the bridge side at 6 o’clock, is entirely new, it relies on the same remontoir mechanism used in the brand’s original Constant Force Tourbillon from 2016.

A view of the Arnold & Son Constant Force Tourbillon 11, revealing the remontoir spring, satellite pinion with locking star, and the rotating carrier. When the star is released, the satellite rotates against the fixed wheel, causing the carrier to advance and rearm the remontoir spring, which then delivers steady torque to the tourbillon

Grönefeld 1941 Remontoire, 2017

From a purely visual spectacle perspective, I think Bart and Tim Grönefeld’s eight‑second remontoir is one of the most awesome timepieces ever created. Before we dive into the dial side — where their three‑armed flying regulator disperses the otherwise violent energy of the gear train rewinding the remontoir spring, and locks it in place for eight seconds before releasing it again — let’s first take a closer look at the movement side of this stellar timepiece. Says Bart Grönefeld, “The idea came from our grandfather, who used to service all the turret clocks in our town. These all had remontoirs, not to combat uneven torque from mainsprings, because many of these don’t have a mainspring, but to eliminate errors caused by other influences.” The Grönefelds’ movement is very clear, because it shows you just enough to be dazzling to the eye, but also hides some very key elements. Let’s first point out how the system works. The mainspring transmits power through the gear train to a wheel in the center of the remontoir assembly, which is mounted on a steel bridge that has “eight‑second remontoir” engraved in negative relief. This wheel features a small ruby pinion and a differential wheel.

The Grönefeld 1941 Remontoire is equipped with what is perhaps the most complex remontoir in watchmaking today

What is not immediately visible is a coiled remontoir spring that connects the pinion to a drive wheel hidden underneath the assembly. This drive wheel, in turn, is geared to the seconds wheel, and is engaged by the seconds wheel’s pinion. Importantly, the drive wheel is driven only by this remontoir spring. The pinion runs together with the drive wheel for eight seconds.

When the remontoir is released, the pinion rotates counterclockwise to rearm the remontoir spring. When it rotates counterclockwise, the differential wheel — fitted with gear teeth on its outer rim — carries this rim along with it. The differential wheel is designed to only rotate counterclockwise; turning clockwise would lock it in place. Because it is geared to the rim, its counterclockwise motion drives the wheel forward, rewinding the spring and maintaining constant force.

Grönefeld’s eight-second remontoir mechanism

After eight seconds, the ruby pallet on the first arm of the three‑armed lever rotates into position and locks the rim in place again. If you look closely, you’ll notice that during this action, the pallet actually skips every other tooth before locking in place. (More on that shortly.) It’s important to note that the function of this toothed rim is to create the eight‑second interval at which the remontoir spring is rewound. OK, but how exactly does the remontoir get rearmed? Says Bart Grönefeld, “What you don’t see on the front side of the watch is a ruby, which lifts this three‑ armed lever every eight seconds to allow the remontoir spring to rewind. The job of the three‑armed lever is to skip every other tooth on the rim it interacts with.” Why does it skip every other tooth?

The Grönefeld brothers, Bart and Tim

Aha, good question. Grönefeld says, “This was necessary to create an eight‑second remontoir, because the watch is vibrating at 21,600vph. Otherwise, if the palette engaged every tooth, you would have something like a 7.6‑second remontoir.” So, what’s with the spinning three‑ armed regulator on the front of the watch? Says Bart, “That is a kind of flying regulator that disperses the energy from otherwise violent action, when the palette re‑engages the tooth and locks the remontoir in place again. It’s actually very cool, because how much this arm spins also tells you the state of wind for the mainspring. If it’s fully wound, the arm spins a lot as the action is powered by the gear train and the energy is a lot. When the mainspring winds down, it spins a lot less. Incidentally, we use a Maltese cross stopwork to ensure that the mainspring energy is always sufficient to rearm the remontoir.”

OK, returning to the movement side, you’ll see two more pallets. These engage a cam driven by the gear train, which causes the pallet to skip every other tooth and engage the correct one. As mentioned earlier, the drive wheel powers the seconds wheel — though you don’t see it, as it’s hidden on the dial side. This seconds wheel engages the pinion of the escape wheel, which then impulses the balance.

Is this system very complex? Absolutely. Bart Grönefeld laughs and says, “If we had agreed to use a 7.6‑second remontoir, which would have been very close to the speed of the system Harrison used in H4, it would have saved us a lot of parts. But Tim and I wanted it to be eight seconds because, in our perception, this symbolized good luck. Also, we felt eight seconds was the perfect duration. On a one‑second remontoir, you don’t really see a lot. On our watch, it’s a little theater.”

Amusingly, when Hodinkee made its limited edition of the remontoir, they decided to cover this entire mechanism, despite it being the raison d’être for this watch. When asked about this, Grönefeld replies, “Well, it was 2017 and we had announced we would make 188 of these movements. We had sold about 50 and we had concerns about selling the rest. The partnership with them brought a lot of visibility to the project. We even had orders from places like Nepal.” But did he like the idea of covering the flying regulator? Grönefeld replies, “In the end we just did what they wanted.”

Now that the remontoir has been discontinued, there are innumerable requests for its revival. When asked if he and Tim might consider doing an updated version, Grönefeld replies, “I could tell you but then I would have to kill you.”

Greubel Forsey Différentiel D’égalité, 2018

Incredibly, the technology underlying this amazing timepiece was first presented all the way back in 2009 as part of Greubel Forsey’s Experimental Watch Technology (EWT) program, which also yielded varying forms of horological dopeness, including escapements made of synthetic diamonds that require no lubrication. The theory underlying the Differential d’Égalité is that even a one‑second remontoir doesn’t deliver perfectly consistent pulses of energy to the escapement with each beat of the balance. Instead, the tension in the remontoir spring varies over the course of its cycle, causing the torque delivered to the escapement of a 3Hz watch (six beats per second) to be stronger on the first impulse and gradually weaker by the sixth impulse as the spring unwinds. (Other brands have addressed this issue with constant escapements, where the impulse delivered to the balance is itself regulated by a spring mechanism — but more on that later.)

Greubel Forsey Différentiel D’égalité

A sketch of Greubel Forsey’s Différentiel d’Égalité movement

Co-Founders Stephen Forsey (left) and Robert Greubel (right)

Stephen Forsey explains that the Differential d’Égalité overcomes this in the following way: “Power flows down the gear train to two output paths. The energy is distributed evenly between them by the differential mechanism. One seconds wheel sends impulses to the escapement. The other output path sends energy to a jumping seconds indicator. Over the course of the watch’s six beats per second, based on its 3Hz frequency, the differential ensures that the quality of power to the escapement remains consistent by varying the torque of the output path to the jumping second, which has no effect on this indicator.”

Andreas Strehler Trans-Axial Remontoir Tourbillon, 2018

To me, the Trans‑Axial Tourbillon is a work of absolute genius. But before we get to it, let’s clear up something. When the Kodo Constant Force Tourbillon was first launched, it claimed to be the very first to place its remontoir on the same axis as the tourbillon cage. It was not, and Grand Seiko has stopped communicating that, because it was Strehler’s Trans‑ Axial Remontoir Tourbillon that was the very first to achieve this.

Andreas Strehler Trans-Axial Tourbillon

Strehler’s watch has a very interesting construction. Instead of placing the remontoir to the side of the tourbillon, it places it underneath the tourbillon, meaning that power comes from the watch’s two mainsprings to a large gold drive wheel known as the “petite moyen,” or intermediate wheel, which powers the pinion of the remontoir assembly — more specifically, the pinion of the satellite arm and wheel, which is the only element that is under the direct influence of the mainspring.

An explosion view of Andreas Strehler’s Trans-Axial Tourbillon with the remontoir mechanism located beneath the cage. Attached to the base of the cage is a lever with a stopping jewel which locks and unlocks a star wheel that is attached to a satellite arm which sits on the cage pinion. As the lever rotates along with the tourbillon cage, the tip of the jewel slides past one tooth of the star wheel, releasing the remontoir spring, allowing the star to rotate forward by one step until the next tooth of the star contacts the jewel.

The remontoir has been effectively flipped upside down: the remontoir spring is positioned between the satellite arm and the base of the tourbillon cage. The spring, which is recharged every second, powers the rotation of the cage. As the cage turns, it drives the escape wheel around a fixed fourth wheel, which in turn impulses the balance wheel. The result is an incredibly intelligent integration of the remontoir and tourbillon into a single assembly.

Grand Seiko Kodo Constant Force Tourbillon, 2022

Launched in 2022 and winner of that year’s GPHG Chronometry Prize, the Kodo Constant Force Tourbillon was an absolute revelation. In principal, it is not dissimilar from the remontoir d’égalité that was created by Andreas Strehler. But its execution is, in fact, quite different. From what I understand, this mechanism was independently conceived by its creator Takuma Kawauchiya. It’s also worth mentioning that Kawauchiya and Strehler share a mutual respect and have a very friendly relationship that underscores the collaborative spirit within the horological community.

How does the Kodo work? Instead of a satellite arm, as you have in Strehler’s remontoir, you have an entire dual‑cage system. The outer cage, driven directly by the gear train, houses the remontoir spring and features a C‑shaped steel ring with a pallet jewel. This pallet jewel is in contact with a fixed ceramic stop wheel, which functions like a stopping mechanism, regulating the release of energy to the main tourbillon cage. The inner (main) tourbillon cage is under the power of the remontoir’s auxiliary spring, which is rearmed every second. It is only the remontoir spring that provides direct power to this primary cage.

Grand Seiko Kodo Constant Force Tourbillon SLGT003

How does that happen? Well, the tourbillon cage is smoothly rotated once every 60 seconds by the remontoir spring, which connects it to the outer cage. While it does this, the outer cage stays in place, held by the locking action of the C‑shaped steel ring with pallet jewel interacting with the fixed ceramic stop wheel. As the tourbillon cage turns, the pallet jewel disengages from the stop wheel, allowing the remontoir cage to advance and recharging the remontoir spring.

The power of the mainspring wants to drive the outer cage, but it can’t while it is locked in place. When it is released, this cage jumps forward by one increment, recharging the remontoir spring until it is once again locked when the pallet jewel engages the next tooth of the stop wheel. In so doing, the outer cage rewinds the remontoir spring, which then provides consistent torque to the inner tourbillon cage. The really cool thing here is how both cages in the system interact with each other, with the outer cage leaping to catch up with the inner tourbillon cage over and over each second like two dancers interacting on a stage. Accordingly, the outer cage is fitted with a jeweled indicator on one of its arms to act as a deadbeat seconds indicator.

Meanwhile, the inner tourbillon cage drives the escape wheel around the fixed fourth wheel. So, it would not be correct to say that the one‑second remontoir here directly drives the escape wheel, as in the Pratt/Gafner model (which will be detailed later), but that it drives the cage, which in turn drives the escapement, which impulses the balance wheel. Clearly, every effort was made to keep every component in this assembly as light as possible, hence the ultra skeletonized escapement wheel created with MEMS (Micro‑Electro‑Mechanical Systems) technology. The end result is a watch that is not only a work of technical brilliance, but also extraordinarily beautiful to watch.

In the Grand Seiko Kodo, the remontoir cage houses the tourbillon on the same axis

Bernhard Lederer Central Impulse Chronometer, 2022

There are a lot of reasons why I love Bernhard Lederer’s Central Impulse Chronometer. Its twin 10‑second remontoir d’égalités are just one reason. Let’s begin with the fact that Lederer is obsessed with escapements and is making a series of watches dedicated to the great “Masters of Escapement.” The first escapement he decided to tackle was George Daniels’ Independent Double Wheel Escapement. This was, in turn, inspired by Breguet’s natural escapement that was designed to operate without lubrication and featured two wheels and an impulse lever between them.

Bernhard Lederer in his Saint-Blaise atelier

Now, several watchmakers today, including Kari Voutilainen and Laurent Ferrier, have utilized the natural escapement concept in their watches. But to Lederer, there is one major issue with this: the natural escapement, rather than two wheels, actually needs four wheels to function, with the two escape wheels and the two drive wheels taking power from the train and allowing them to interact. He explains, “You need 16 times more energy to the whole system to get this to function properly.” Instead, Lederer opted for the system created by George Daniels, which was used in his famous pocket watches like the Space Traveler, where each wheel is powered by its own barrel and gear train. This allowed Daniels, as Lederer explains, to “invent a system to accelerate the two wheels without having to connect them through additional wheels.”

Bernhard Lederer Central Impulse Chronometer 39mm

While there are several improvements made by Lederer to get the Independent Double Wheel Escapement to function in his Central Impulse Chronometer, one key innovation was the use of two remontoir d’égalités, each sitting between the third and fourth wheels of the respective gear trains. The two remontoirs are rearmed every 10 seconds, with one rearming first and the other following five seconds later. The key to the remontoirs is they allow perfectly symmetrical energy delivery to each of the escape wheels, ensuring uniform pulses to the balance wheel. Such constant force is particularly important when the torque from the mainspring diminishes. He explains that, at low amplitude, “the liberation of one wheel can provoke the teeth of the active escape wheel to slip in front of the impulse‑taking pallet — which is on the balance staff — and then you miss one, maybe two escape wheel teeth; it will impact precision. For me, this was a real problem.”

Lederer’s latest remontoir, featured in the CIC 39mm, localizes all of its components on the third wheel, which features pillars acting as a stop wheel. Coaxially mounted is the remontoir wheel, connected via a spiral spring and geared to a pinion carrying a flywheel. During operation, the flywheel rests against a pillar, locking the remontoir wheel in place. As the third wheel continues to rotate, it moves the pillar out of the way, releasing the flywheel and allowing the remontoir wheel to rotate. The spring then unwinds, delivering constant torque to the downstream gear train. The cycle ends when the flywheel strikes the next pillar, halting the remontoir wheel and beginning the spring’s re-tensioning phase.

The release mechanism is positioned directly on the same axis as the remontoir spring, allowing the remontoir to be triggered precisely at the point where energy is introduced.

Lederer points out that in the 2018 Charles Frodsham Double Impulse Chronometer, which also uses this style of escapement, danger is averted by simply stopping the watch after around 36 hours. He describes this solution as akin to addressing the symptoms but not the underlying problem. The real solution came with the use of his twin remontoirs, a testament to his deep understanding of watchmaking know‑ how.

George Daniels’ 15-second Remontoir, 1975

George Daniels is best remembered for inventing the Co-Axial escapement, but just as significant was his role in preserving the art of mechanical watchmaking through some of its darkest decades. Above all, Daniels embodied a philosophy of horology rooted in precision, elegance, and craftsmanship of the highest order. While many of his achievements have rightly taken their place in the modern canon, some remain in the shadows. Among them is the remontoir, which he installed into a tourbillon pocket watch of his own making in 1975.

Dr George Daniels

Daniels saw in the remontoir a kind of mechanical idealism, a solution that existed not out of necessity but out of a commitment to horological excellence. In his book Watchmaking, he wrote, “The use of the remontoir is by far the best method of smoothing the power supply, but it is complex and costly to make. For this reason, watches with remontoirs are very rare and this, combined with their attractive action, gives them a special place in the affections of the connoisseur of mechanics. The fact that the mechanism is quite unnecessary merely adds to its charm.”

The watch in question is equipped with a one-minute tourbillon with a 15-second remontoir, double barrels with an annual calendar disc and an equation of time cam mounted over the barrel bridge, a screw differential for the power reserve indicator, and a reversed spring detent escapement.

George Daniels’ tourbillon remontoir pocket watch created in 1975. It features a silver engine-turned dial with sectors for the Equation of Time and the state of winding

It has a one-minute tourbillon with a 15-second remontoir, twin barrels with an annual calendar disc and an equation cam mounted on the barrel bridge, a screw differential for the power reserve and a reversed spring detent escapement

The remontoir spring is mounted on the fixed fourth wheel, physically positioned beneath the tourbillon cage. The third wheel in the going train powers both the cage pinion and a remontoir train that is unlocked by the tourbillon cage itself. The lower cage of the tourbillon is designed with four evenly spaced protrusions, one every 90 degrees. Each protrusion carries a small pin. As the tourbillon cage rotates, completing one revolution every 60 seconds, each pin trips a pallet jewel on the tip of a lever once every 15 seconds.

The tourbillon cage has four protrusions, each carrying a small pin that trips a pallet jewel on the tip of a lever. A secondary lever attached to it then releases the remontoir train to power the remontoir spring located beneath the tourbillon cage

This lever is rigidly fixed to a second lever. When the tourbillon pin lifts the primary lever, the motion directly affects the second lever, whose end releases the remontoir train. This allows the remontoir gear train to rotate and rewind the remontoir spring. This clever use of the rotating tourbillon cage essentially uses the motion of the cage itself to control the rewinding of the remontoir spring. To manage the speed of rewinding which could otherwise occur too quickly, there is a fly governor at the end of the remontoir train. As the remontoir mechanism is spread across several stages – with the spring located beneath the tourbillon and the release occurring upstream in the remontoir train – its operation, together with the tourbillon cage that governs the release, should make for an engaging visual spectacle.

Daniels employed a remontoir in his work only twice – once in this watch, and again in a tourbillon pocket watch with a Co-Axial escapement that remained unfinished at the time of his death.

Roger W. Smith’s 15-second Remontoir, 2000

Roger Smith, one of the greatest living watchmakers and the sole apprentice to George Daniels, once created a 15-second remontoir in a pocket watch known simply as No. 3.

Roger W. Smith

It was commissioned by his very first client in 1997 and was only the third watch he produced under his own name, following his inaugural creation, a tourbillon pocket watch with a spring detent escapement, and his second, an extraordinary perpetual calendar tourbillon, also with a spring detent escapement, which would go on to fetch $4.9 million at Phillips in 2023.

Completed in 2000, No. 3 was, by contrast, deceptively modest. A time-only pocket watch with dual barrels, a power reserve indicator, and a Peto cross detent escapement, it forwent the tourbillon in favor of a 15-second remontoir.

The remontoir spring, along with a control wheel shaped as a four-pointed star, are located beneath the fourth wheel in the going train. Power flows from the third wheel to the pinion of the fourth wheel, which drives the escape wheel as usual. Simultaneously, power is also transmitted from the third wheel pinion to a separate remontoir train that includes a stop wheel and a fly governor.

The four-pointed star wheel completes one full revolution every minute and is responsible for unlocking the remontoir mechanism and rewinding the remontoir spring every 15 seconds. When one point of the star engages the release lever, it unlocks the stop wheel, allowing the remontoir spring to be rewound by the going train. The fly governor moderates the speed of the rewinding action, ensuring that the spring is tensioned smoothly and without shocks that could disturb the timekeeping.

Once rewound, the stop wheel immediately locks the remontoir train again, holding the freshly tensioned spring in place. The remontoir spring then unwinds over the next 15 seconds, delivering a steady torque to the escapement.

The control wheel triggers the unlocking and rewinding of the remontoir spring every 15 seconds, while the stop wheel immediately locks the remontoir train again, ensuring that the rewound spring delivers a steady force to the escapement until the next cycle.

Derek Pratt/Robert Gafner Reuleaux Triangle 1-Second Remontoir D’égalité

There is one legendary watchmaker whom I associate with the remontoir as closely as François‑Paul Journe. The difference is that, unlike Journe, he never placed the mechanism inside a wristwatch, instead focusing on pocket watches made under his own name and during his tenure as technical director of Urban Jürgensen from 1982 to 2005. I refer, of course, to Derek Pratt and his Reuleaux triangle Remontoir d’Égalité unveiled in 1981, which is my single favorite design for a constant force mechanism. Why? Well, first of all, it is mounted onto the cage of the tourbillon and acts on the escape wheel. There is a theory that the closer you place the constant force mechanism to the balance wheel, the better the performance, as power generated by its very small spring is not robbed by the friction of traveling through multiple gear wheels.

Derek Pratt’s signature remontoir, in which the mechanism is mounted directly on the escape wheel

In other words, placing the constant force mechanism close to the balance wheel reduces power loss and maximizes efficiency. And probably the ultimate examples of this principle are the constant escapements created by both Girard‑Perregaux and Ulysse Nardin which deliver six precise impulses of energy per second at their 21,600vph or 3Hz vibrational speeds. However, so far, these escapements can only be crafted using silicon. As someone who loves old‑ school watchmaking, my preference is for mechanisms made using traditional materials. That’s why, to me, the series‑ produced Derek Pratt tourbillon with cage‑mounted remontoir d’égalité — first realized by Urban Jürgensen and Kari Voutilainen — is simply the ultimate expression of constant force dopeness. Let me explain why.

The design of Pratt’s remontoir d’égalité is based on a remontoir created by Robert Gafner at the watchmaking school in La Chaux‑de‑Fonds in the 1930s. It features a Reuleaux triangle and a fork. A Reuleaux triangle is a curved triangle with a constant width. It can perform a complete rotation within a square while at all times touching all four sides of the square. However, although it covers most of the square in this rotation process, it fails to cover a small fraction of the square’s area, near its corners. Notably, it has the smallest possible area of any shape that can maintain constant contact with all four sides of a square during rotation.

Derek Pratt

Why is this interesting? Well, in 1981, Derek Pratt achieved something that even the mighty Abraham‑Louis Breguet was never able to do, and that was to integrate a constant force remontoir directly into the tourbillon. (Breguet patented the remontoir d’égalité in 1798 and the tourbillon in 1801.) Today this has also been achieved by François‑Paul Journe and it’s worth taking the time now to understand how he and Pratt delivered constant force to their tourbillons. In Journe’s case, his constant force mechanism delivers power to the wheel that drives the pinion of the tourbillon cage. The mechanism rewinds itself every second and, notably, it is actually this wheel that the seconds hand on his deadbeat seconds watches is fixed to.

Derek Pratt Oval pocket watch

In contrast, Pratt’s design uses a constant force mechanism that sits in two parts on top and below the escape wheel itself, and is mounted to the tourbillon cage. Just from a pure micro‑mechanical perspective, the complexity of this is simply crazy. On top of the escape wheel is a Reuleaux triangle and a fork shaped like an open square. The system includes an anchor with two pallets. Below the escape wheel is the remontoir stop wheel with three spokes and three teeth on its outer rim that interact with the pallets. Between the remontoir wheel and the escape wheel is a tiny spring, which is the sole energy source in the entire movement that powers the escape wheel. What happens is that as the escape wheel turns, spring tension is released from this spring. But the remontoir stop wheel is under the influence by the gear train and wants to turn. It doesn’t because it is locked into place by the Reuleaux triangle’s constant contact with the fork.

Each time the Reuleaux triangle rotates, it allows the tooth of the remontoir wheel, which is locked against the remontoir pallet, to disengage. As the tooth is released, the remontoir wheel moves forward, changing the position of the anchor so its second pallet catches the next tooth of the remontoir wheel. This moment of freedom releases the energy of the gear train, which turns the remontoir wheel by 120 degrees and rewinds the spring. Super dope, right? If you’ve just shouted out, “Hell yeah!” I am in agreement. Pratt’s ultimate evolution of this design was the incredible double remontoir on double wheel escapement on his tourbillon prototype watch, which he entered in the 1997 Breguet Prize.

Ironically, Derek Pratt himself never constructed a wristwatch using his signature Reuleaux triangle remontoir d’égalité. At the moment, there are three brands that use this system in wristwatches combined with a standard, i.e. non‑tourbillon, format balance wheel: the Derek Pratt watch made by Luca Soprana, the Lang & Heyne Friedrich II Remontoir models and the Ferdinand Berthoud Chronomètre FB 2RE. All three executions are pretty damn magnificent to behold. But as of 2025, there is one watch that now expresses the ultimate execution of this amazing accomplishment, and that is the mind‑ blowingly epic, magnificently decorated, technically brilliant Urban Jürgensen UJ‑1 designed by Mister Kari Voutilainen for Alex and Andy Rosenfeld.

Urban Jürgensen UJ‑1

Kari Voutilainen and Alex Rosenfield

Ferdinand Berthoud FB 2RE Fusée-And-Chain And Remontoir D’égalité, 2020

My favorite wristwatch using the Pratt/ Gafner type of remontoir by far is the Ferdinand Berthoud FB 2RE, which pairs the remontoir with a stunningly finished fusée and chain. The question you might ask is, is this like a man wearing both suspenders and a belt? Well, actually no, because some of the most famous marine chronometers including Harrison’s H4 use both the fusée as well as a constant force mechanism. The architecture of the Ferdinand Berthoud FB 2RE is one of the most beautiful I’ve ever seen, with a layout that is simultaneously unconventional but magnificent to behold.

The Ferdinand Berthoud Chronomètre FB 2RE features all three constant force devices: a stopwork, fusée-and-chain and a remontoir

At the top of the movement, you have the barrel and the fusée-and-chain that links them together. The massive balance wheel sits on an arrow‑shaped bridge in the center of the movement, which reminds me a bit of the Charles Frodsham watch. At the very bottom of the movement, you have two bridges facing each other. One holds the remontoir anchor (or pallet fork), while the other holds both the escapement and remontoir wheels. Watching them interact, exactly as I’ve described above in the section on Derek Pratt, is one of the most spectacular sights in modern horology. But it is the movement design and the level of finish that elevates this timepiece to the realm of the horological gods. Also, as it is the very first serially produced wristwatch to feature a fusée-and-chain combined with a remontoir system, it is worthy of significant historic status.

Saxony Style: Lang & Heyne Friedrich II Remontoir, 2022

One watch that flies very much under the radar but is cool as hell is the Lang & Heyne Friedrich II Remontoir. Checking out the movement, the first thing you’ll see is that as opposed to the Berthoud or Pratt watch, here, the gear train is visible. Lang & Heyne has some exquisite finish and you can see the polished “wolf’s teeth” on the barrel and ratchet wheel. A beautifully designed bridge retains the jewels set in chatons, which are, in turn, fixed with heat‑ treated purple screws for every wheel in the train.

Lang & Heyne Friedrich Ii Remontoir

A steel‑capped bridge holds the escape wheel and the remontoir wheel, while a small dedicated steel bridge holds the remontoir anchor. These interact with the huge balance wheel that’s fitted to a Saxon‑style hand‑engraved cock with a pinion riding in a large synthetic diamond. While, typically, a Saxon‑style watch would have a three‑quarter plate, the bridge here was created to give the owner an unencumbered view of the remontoir mechanism. Also note that while, in principle, it is inspired by the Derek Pratt/Robert Gafner constant force mechanism, the Lang & Heyne is very much its own design featuring ruby pallets that the Reuleaux triangle rotates within. Another cool touch is that on the dial side, the seconds hand is filled with lume so that you can tell it’s deadbeat even in the dark.

Derek Pratt Remontoir D’égalité By Luca Soprana, 2023

Luca Soprana currently has the rights to make watches under the name “Derek Pratt” and has, accordingly, created this watch. Actually, I should say he took over from a longstanding project that had many notable names connected to it, and to his credit, was able to successfully bring it to life. Here, you have twin suspended barrels, a sexy open‑worked bridge that seems to be a reference to the open‑worked bridge that he used for the twin barrels of his pocket watch movements, which have been featured on the vintage watch platform, www. lifeonthewrist.com.

Derek Pratt Remontoir d’Egalité by Luca Soprana

In contrast, as Soprana’s watch actually has suspended barrels, this bridgework seems to be primarily decorative. There is a big jewel fitted to it that, I presume, is for the first wheel of the gear train, hidden on the opposite side of the plate. These hidden gear train designs are very much in vogue at the moment, popularized by brands such as MB&F. The balance wheel is just under the two barrels, and the escape wheel and remontoir anchor are on two separate bridges similar to the Berthoud watch.

One individual whom we should mention is Stewart Lesemann, a longtime friend of Soprana who, incidentally, was also one of the watchmakers who helped to rescue MB&F’s Max Büsser when the new owner of STT returned him a box of parts for his HM1 instead of the completed movements. Lesemann was very much involved in the development of the Derek Pratt Remontoir d’Égalité with Luca Soprana.

Urban Jürgensen Uj-1 Tourbillon With Remontoir D’égalité, 2025

I’ve written about the Urban Jürgensen UJ‑1 watch in much greater detail here. Nonetheless, I must reiterate the historic significance of this timepiece. It was Derek Pratt, the technical director of Urban Jürgensen from 1982 to 2005, who united the remontoir with the tourbillon by mounting the constant force mechanism directly onto the cage and co‑axial with the escape wheel. His great achievement was not just his technical capacity to achieve this, but also that, from an aesthetic perspective, it was simply sublime to look at. This mechanism is featured in many of his pocket watches and the majority of the tourbillons he created for Urban Jürgensen. It is also the central technical device in his most famous timepiece, the legendary Oval Pocket Watch. Importantly, as Pratt was unable to finish this watch due to illness, its legacy was passed to Kari Voutilainen, the only man he trusted to complete this project.

The Urban Jürgensen UJ-1 is a re-creation of Pratt’s Oval pocket watch

Says Kari Voutilainen, “One of the defining experiences of my career was completing the assembly and finishing of the masterpiece Urban Jürgensen Oval Pocket Watch, which Derek Pratt had begun to work on in 1982 but was unable to complete after he became ill. This extraordinary timepiece, which recently achieved a record price at auction, embodies everything Urban Jürgensen stands for — chronometric excellence, uncompromising craftsmanship and an innovative spirit.”

It is fitting that the Oval Pocket Watch is the direct inspiration for the UJ‑1, which becomes the very first series‑ produced timepiece to feature Pratt’s tourbillon cage‑mounted remontoir d’égalité. From a perspective of movement architecture, with its stunning hanging barrel and single black‑polished steel bridge bisecting the movement and forging a dramatic horizontal line across the movement, it is stunning to behold. It is without a doubt in my mind that the UJ‑1 will be one of the most historically important timepieces of the modern era, thanks to its rich lineage and sumptuous execution.

The Constant And Anchor Escapements

We’ve discussed the different types of remontoir d’égalités used in wristwatches today. To summarize, there are three types: the model using a flat‑bladed spring created by François‑ Paul Journe; the Derek Pratt/Gafner model, which is most poignantly expressed by the Urban Jürgensen UJ‑1 tourbillon with remontoir d’égalité; and the Andreas Strehler‑designed remontoir d’égalité with its satellite wheel and stopping jewel. There is, of course, also the wonderful Kodo‑style remontoir with two tourbillon cages. All of these are amazing but all are one‑ second remontoirs, meaning that their springs are rearmed each second before they release energy through the seconds wheel to the escape wheel. As Stephen Forsey points out, the energy during this one second over each impulse to the escapement is, in fact, variable as spring tension changes with each beat. So, is there a solution to provide even pulses of energy directly to the balance wheel?

This was a question that plagued Rolex watchmaker Nicolas Déhon back in 1996. Déhon was commuting by train when he had an epiphany while absentmindedly flicking his ticket between his fingers. A blade spring, kept slightly flexed between two fixed points could, like his train ticket, be made to snap back and forth, delivering a predictable pulse of energy each time. If the bit of cardboard between his fingers could be transformed into a source of energy for the balance, it might be the answer to the constant force riddle. The process of development began, and though Déhon and Rolex were able to cobble together a prototype, and even took out a patent for this constant force escapement (granted in 1999), its design was still slightly ahead of its time. The materials needed to build a reliable and effective version were not available.

By 2008, Déhon had taken his idea to Girard‑Perregaux, which enthusiastically embraced it and, under the leadership of Stéphane Oes, finally saw the Constant Escapement through to fruition. The key to its success was the introduction of silicon, that hard, fatigue‑resistant material used by more and more watch companies, mainly for balance springs. The 1999 prototype used a two‑piece metal alloy design, which ultimately proved to be its weak point. The 2008 GP version used a one‑piece frame, lever and blade spring made from silicon by means of photolithography. Déhon remained at GP long enough to see his inspiration tick to life, and Oes then spent the next four years with his team refining it and making it fit into a watch. That watch is the Constant Escapement.

The original Girard-Perregaux Constant Escapement

Though it may seem confusing at first, the basic principle is simple. As the balance swings, it passes through a tiny fork which is attached to the impulse lever. In doing so, it causes the S‑shaped blade spring to “snap” from one S‑curve to its opposite. As it does so, it delivers energy to the balance. Once the balance has cleared the impulse lever, one of the curved faces of one of the two escape wheels makes contact with a jewel on the impulse lever, and the curve begins to push the S‑curve back towards the previous shape — but before it can actually snap back, the lever is arrested, as one of its locking jewels makes contact with one of the escape wheel teeth. The blade spring is now armed and ready to snap to its opposite configuration as the impulse jewel trips the lever.

In 2023, Girard‑Perregaux created a refined version of the Constant Escapement watch that features seven new patents and 14 less parts, according to the brand. The resulting timepiece, the Neo Constant Escapement, was impressive but plagued by one major challenge. That was its 45mm in diameter size. At this size, the watch was somewhat out of step with the prevailing taste for more classic dimensions, even when it comes to highly complicated technical timepieces. The problem relates to the size of the Constant Escapement’s architecture that takes over the entire bottom half of the watch. Is it possible to create an escapement with the same efficiency but in a far more compact size? Well, the answer to this is clearly yes, because it has already been achieved by Girard‑Perregaux’s sister company, Ulysse Nardin.

The self-starting Neo Constant Escapement

Ulysse Nardin had a massive headstart on the rest of the watch industry when it comes to silicon technology. Why? Because it was a pioneer in the material, becoming the first Swiss brand to implement it for the escapement wheel in its legendary watch, The Freak. This eventually led to its creation of a company called Sigatec, which really is light years ahead of anyone else when it comes to silicon technology. In 2014, just one year after Girard‑Perregaux unveiled the Constant Escapement, Ulysse Nardin launched its Anchor Escapement, which pretty much does everything the GP escapement does but in a much more compact manner. It consists of a circular silicon frame with two buckled blades attached to the anchor. Even cooler, this system works in conjunction with a superb silicon escapement wheel and silicon balance wheel with a metal rim. The resulting escapement is impervious to magnetic fields, requires no lubrication, is much more mechanically efficient than a Swiss anchor escapement and so small it can even be placed inside of a tourbillon, which Ulysse Nardin has already done to spectacular effect in the amazing yet totally ignored UN Anchor Tourbillon, one of the most important timepieces in recent memory that no one paid any attention to.

Ulysse Nardin Anchor Escapement

That brings up the question, “If these escapements achieve better constant force results than spring remontoirs, why are they somehow less exciting or popular?” The answer, to me, is that spring remontoirs remind us of classic watchmaking. They are, in essence, like building the world’s most beautiful woodhull sailboats out of traditional materials. From a performance perspective, they are not fast at all, but they are about human beings expressing the very highest level of craftsmanship and technical innovation within tradition boundaries. Once you introduce silicon, which can be created into any hyper complex form at almost any size, you create a kind of hybridization of technical and modern watchmaking, which somehow doesn’t create the same romance as a traditional watch — at least, that’s my take on it.

But as you read earlier, Andreas Strehler first got inspired for his remontoir d’égalité from a mechanism built on an escapement wheel. So, is it possible that we will see traditional spring remontoirs that operate at a sub‑second rewinding state? It seems so, yes. In fact, according to Valérien Jaquet, this is already something he has implemented in the Jacob & Co. Astronomia 4th Dimension; however, as I’ve yet to see this mechanism up close, I cannot yet report in detail.

A. Lange & Söhne And The Constant Force Mechanism

If there is any one major brand that you could closely associate with the constant force device, it would be A. Lange & Söhne, a brand whose ascendance in the 20th century can be attributed to the genius of a man who brought it back to life following Germany’s reunification — Günter Blümlein. This all started, of course, with the amazing Pour le Mérite Tourbillon, which was one of the timepieces unveiled at the 1994 press conference relaunching the manufacture. You can only imagine how blown away the audience was when they saw a tourbillon driven by a barrel featuring a fusée and chain. Says the amazing Carole Forestier‑Kasapi, the current Technical Director of TAG Heuer who was working at Renaud & Papi, alongside Andreas Strehler, when they were tasked with creating this device, “The challenge of making the fusée and chain for a wristwatch‑sized timepiece was absolutely crazy, but we got there in the end.”

Lange would use spring remontoirs in watches such as the Lange 31, with 31 days of power reserve and a single spring barrel. The obvious benefits in a watch where the quality of power from the mainspring might deviate over this time period are obvious. Lange also used a remontoir‑type constant force mechanism in the Richard Lange Perpetual Calendar. It appears to utilize a Pratt/Gafner‑style Reuleaux triangle that is rearmed every 10 seconds for 14 days of power reserve. The Zeitwerk uses a 60‑second remontoir to aid in the digital jump of its time‑telling function. The Richard Lange Jumping Seconds uses a five‑star pinion on an escape wheel with flirt (six oscillations per second), in combination with remontoir d’égalité.

Richard Lange Perpetual Calendar

The remontoir mechanism in the Richard Lange Perpetual Calendar

Zeitwerk Date

Remontoir mechanism in the Zeitwerk