Breguet Expérimentale 1: Anatomy Of A Magnetic Escapement
10 min read
In this day and age, it’s impossible to escape magnets. They’re literally everywhere.
Practically, all the things that surround us - from our very dear smartphones, laptops, handbags, and even credit cards, house a magnetic field. And yes, the planet we’re perpetually trying to escape, that too has a giant geomagnetic field.
So, we’re too enveloped in the effects and consequences of magnetism.
In regards to our everyday lives, the omnipresence of magnetism doesn’t pose any real threats, but in context of the objects that form our passion and, in my case bread and butter, the phenomenon has been met with a bit of, let’s say, hostility.
Magnetism has always been a watchmaker’s and a watch’s shadowed adversary, causing an erratic reaction to timekeeping function in case of the latter and as a consequence, a few more hair lost in case of the former.
So, how can one of watchmaking’s most traditional adversaries become the impulse for its future innovations.
The answer will be a technical explanation of the magnetic escapement in Breguet’s Expérimentale 1.
From Enemy To Engine
In the classic narrative, magnetism is simple: expose a steel hairspring to a strong field, the coils stick, the effective length shortens, and the rate runs wildly fast. Generations of watchmakers responded with soft-iron inner cages, non‑magnetic alloys, and, more recently, silicon hairsprings that simply ignore external fields. All of that work assumed one premise: the best magnetic field is the one that never reaches the regulating organ.
Breguet’s Expérimentale 1 inverts that premise. Here, magnetic fields are not an environmental hazard to be excluded, but a deliberately shaped resource, used as the primary medium for locking and impulse in a high‑frequency, constant‑force tourbillon escapement beating at 10 Hz. In a sense, Breguet has taken the problem that defined modern anti‑magnetic watchmaking and pulled it into the heart of the movement as the solution.
The Old Physics: Contact, Friction, Drift
To see what has changed, it helps to restate what has not. In any mechanical watch, the mainspring would like nothing better than to dump its stored energy into the gear train in a few uncontrolled seconds. The escapement’s job is to meter that release into uniform packets, synchronized to the oscillation of the balance.
In the Swiss lever, that metering is done by impacts and sliding contact. The escape wheel teeth lock on ruby pallets, then slide across impulse faces to deliver a push to the balance through the fork and impulse pin. This architecture has two unavoidable consequences:
- Friction and lubrication: Every locking and impulse event consumes energy in sliding contact - lubricants age, surfaces wear, and performance drifts until the next service interval.
- Variable impulse: The magnitude of the impulse depends directly on the torque in the train; as the mainspring runs down, the balance amplitude falls and the rate migrates, even in very good chronometers.
Classical constant‑force solutions - fusées, remontoirs d’égalité, sophisticated stop‑work - attack that second problem by inserting an intermediate energy buffer between the going train and the escapement. They do not, however, eliminate contact in the escapement itself. Breguet’s new system goes after both issues at once.
A Three‑Layer Escape Wheel And A Shaped Field
The magnetic escapement of the Expérimentale 1 starts with an escape wheel that is less “wheel” than stack. There are three coaxial discs:
- Two outer titanium wheels carry continuous magnetic tracks on their inner faces, deposited as rings of rare‑earth material (samarium‑cobalt or neodymium‑iron‑boron) with precisely engineered geometry. (1 and 2 in figure below)
- A central, non‑magnetic “stop wheel” in between provides a mechanically toothed reference layer and participates in locking. (3 in figure below)
Crucially, the magnetic tracks are not segmented permanent magnets glued around the circumference. They are continuous annular bands of constant thickness but variable width. That single design choice - varying the width of a continuous layer - creates what the original Swatch Group patent document for the system describes as “ramps” and “potential barriers” in the field: regions where the repulsive force between track and pallet magnet grows gradually, and discrete locations where that gradient jumps beyond what the train torque can overcome.
The lever, in turn, carries small permanent magnets in what are, to the eye, recognizable pallet bodies. Those magnets are oriented so that like poles face the tracks on the upper and lower escape wheels, producing purely repulsive interactions. The geometry of those interactions - rather than mechanical tooth faces - defines locking, draw, and impulse.
Ramps, Barriers, And The “Magnetic Slingshot”
Think of one pallet magnet hovering over the inner face of an escape‑wheel track. As the train attempts to drive the stack forward, three distinct entities appear:
1: Ramp region: As the magnetic track’s width slowly increases under the pallet magnet, the local field strength and the repulsive force increase smoothly. The wheel continues to advance, but against a rising “magnetic incline,” storing potential energy in the configuration of the field much as a stretched spring stores elastic energy.
2: Barrier: At a specific angular position, the track geometry shifts more abruptly, the patent describes a “barrier of magnetic field with increasing field, whose gradient exceeds that of the ramp.” At that point, the torque transmitted through the train is no longer sufficient to push the system further up the gradient. The escape‑wheel stack simply stops, held in a static equilibrium by repulsive forces alone.
3: Release: Only when the lever is rotated - by the balance acting through the fork and impulse jewel - does the pallet magnet move out of that barrier configuration, allowing the stored magnetic potential to be converted into kinetic energy and transmitted as impulse.
In other words, the wheel is driven towards the barrier by the mainspring, but the barrier itself functions as a non‑contact stop. Energy is accumulated along the ramp and then released into the balance as the lever shifts the relationship between pallet magnet and track. The energy source for impulse is the stored magnetic potential, not the instantaneous train torque.
Hybrid Locking: What Actually Touches What
While all initial coverage and understanding described the system as one with purely magnetic locking and purely contactless operation, subsequent clarification adds an important nuance: the central stop wheel does make brief physical contact with the locking pallet at each drop.
The sequence is as follows:
- As the escape wheel stack advances into the next position, the tooth of the central stop wheel meets the locking pallet and halts its motion.
- The pallet then recoils a minute distance under repulsive force from the “step” at the thick end of the magnetic ramp on the outer wheels - this recoil creates a small, but real, clearance between pallet and stop‑wheel tooth.
- That repulsive lateral component simultaneously presses the lever against its banking pin, providing what Breguet describes as the “magnetic equivalent of draw” - the force that keeps the lever positively locked until the balance unlocks it.
During impulse, therefore, there is no sliding contact between pallet and stop wheel - the lever is already slightly separated, and energy transfer is purely magnetic. The stop wheel’s job is to define a precise, repeatable geometric locking point and to suppress the tendency of repulsive fields to behave like springs - ring magnets bouncing on a shaft rather than settling cleanly.
The escapement is thus hybrid: mechanical at the instant of lock, magnetic during draw and impulse. That hybridization is what makes the system both geometrically well‑defined and effectively frictionless at the critical stages of energy transfer.
Constant Force By Geometry, Not By Spring
The constant‑force character of the Expérimentale 1 arises directly from the ramp‑and‑barrier geometry. The mainspring’s role is simply to drive the escape wheel up the ramp until it reaches the barrier, whether the torque is high (fully wound) or low (near the end of the 72‑hour reserve from four parallel mainsprings), the system always comes to rest in the same angular position.
Because:
- The stopping point is fixed by the barrier gradient, not by available torque.
- The magnetic configuration at that point, and therefore the stored potential energy, is invariant with respect to mainspring state.
Every cycle therefore begins from the same energy state and delivers the same impulse to the balance. The escapement has become a transducer: it converts variable mechanical input from the train into a fixed quantum of magnetic potential, and then reconverts that into a fixed mechanical impulse to the balance.
This is conceptually similar to a remontoir d’égalité, which interposes a small spring between the going train and escapement and charges it to a fixed deflection every cycle. The difference is that Breguet’s system uses a shaped magnetic field as the “spring” and does so without introducing additional wheels, pinions, and friction surfaces in the transmission path.
Architecture At 10 Hz
All of this happens at a balance frequency of 10 Hz or 20 vibrations per second, which places extreme demands on timing accuracy, inertia management, and energy supply. Breguet addresses those demands with several architectural choices:
- A tourbillon carriage with the magnetic escapement integrated, geared via an intermediate wheel so that the cage still makes one revolution per minute and can serve as a seconds display.
- Four mainsprings arranged as two barrels in series, each barrel containing twin springs acting in parallel on the same drum and separated by sapphire disks to avoid inter‑coil friction, yielding 72 hours of reserve at 10 Hz.
- Extensive use of non‑magnetic and amagnetic materials - Breguet’s silicon hairspring, non‑magnetic alloys in the carriage, and carefully shielded magnetic tracks - to ensure that the fields that matter are only the ones the system itself generates.
The result is a tourbillon whose escapement not only runs at an extremely high beat rate, but does so with a guaranteed maximum daily deviation on the order of one second - a figure that’s historically reserved to the best laboratory‑grade chronometers, not wristwatches.
Magnetism In Context: From Anti‑Magnetic To Magnetic
Breguet’s solution does not exist in a vacuum. The company’s own history with constant‑force devices goes back to Abraham‑Louis Breguet’s experimental escapements and his early remontoirs in marine chronometers. More broadly, modern watchmaking’s engagement with magnetism has followed two parallel tracks:
- Defensive: soft‑iron inner cases in early anti‑magnetic tool watches, then non‑magnetic alloys and silicon, culminating in movements rated to thousands of gauss without inner cages.
- Active: Seiko’s Spring Drive, which uses a pair of electromagnets and a quartz reference to brake a glide wheel magnetically, is an obvious example of magnetic regulation in a hybrid mechanical–electronic context.
The Expérimentale 1 is the first wristwatch to exploit static magnetic fields as the working medium of a fully mechanical escapement that is both constant‑force and effectively frictionless at impulse. It is neither an anti‑magnetic watch in the traditional sense nor a mechatronic regulator, instead, magnetism has become one more classical energy domain that can be shaped, quantized, and used in the same spirit as a steel spring or a gravity‑driven remontoir.
Why It Matters?
On paper, the practical gains are impressive but not strictly necessary in a world of thermocompensated quartz. A CHF 320,000, 75‑piece experimental Breguet that keeps time to within a second a day does not threaten the smartwatch on your wrist. Its significance lies elsewhere.
First, it demonstrates that the physics of mechanical timekeeping were not exhausted by the Swiss lever plus hairspring template. By recasting locking and impulse as a problem in field geometry rather than tooth profile, Breguet has opened a new design space: magnetic ramps and barriers, hybrid locking schemes, and field‑based “draw” are now tools available to anyone capable of manufacturing at the required tolerances.
Second, it reframes magnetism not as a contamination to be excluded but as a design parameter to be harnessed. That is a conceptual shift on the order of the adoption of silicon, and it arrives, appropriately, from a manufacture that traces its lineage to Abraham‑Louis Breguet’s original workshop.
Finally, it reminds us that haute horlogerie’s highest calling is not utility but ingenuity. To spend a decade turning the arch‑enemy of the mechanical watch into the medium of an entirely new escapement is, in the best sense of the word, anachronistic. It is also precisely the kind of anachronism that keeps the field alive: not as a technology competing with quartz, but as a laboratory where 18th‑century problems are still being attacked with 21st‑century physics.
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