Sol Invictus by Cabestan & Marc Alfieri : The First Mechanical Watch in the World to Integrate a Perpetual Winding System Powered by Solar Energy

Jointly developed by Swiss luxury watch maker Cabestan & Marc Alfieri , Sol Invictus is the first mechanical watch in the world to integrate a perpetual winding system powered by solar energy.

This spectacular timepiece incarnates the new generation of exclusive watchmaking : three of the leading names in the industry, Marc Alfieri, Jean-François Ruchonnet and Eric Coudray, worked together to create the unimaginable. Sol Invictus, Invincible Sun, god revered by the Roman Emperor Aurelian, is today the name of this extra ordinary creation.

Marc Alfieri, an avant garde watchmaker, is also a major actor in the large scale deployment of solar panels in France. During a meeting with Jean-François Ruchonnet, this experience led him to the idea of combining the astonishing movement of the Cabestan Winch Tourbillon Vertical, with its chain and fusée, drums and vertical tourbillon, and a rewinding system powered by solar energy at a scale never seen before. The vision was to link the Cabestanʼs micromechanics to miniature photovoltaic cells, store energy and then draw upon it as needed, to electro-mechanically set the time and perpetually rewind the movement.

Marc Alfieri, who installs vast surfaces of solar panels capable of generating 100 megawatts of electricity, adapted this technology to Sol Invictus to produce only 100 milliwatts, or one billion times less power. To achieve this, he worked with lʼINES (lʼInstitut National de lʼEnergie Solaire) who recently developed a revolutionary new technique for producing and treating silicium crystals that can be used to produce highly efficient solar cells that are especially suitable for small surfaces and low luminosity. Sol Invictus will have the honour of being the worldʼs first commercial utilisation of this groundbreaking technology.

Two brushless micromotors are employed, one for rewinding the movement and the other for setting the time. Typically used in the medical industry, they have a diameter of only 1.9 mm and a length of 5.5 mm. A miniature controller regulates and amplifies the electrical charge, manages the two micromotors via a programmable oscillator and assures the direction and the speed of the motors. To activate and deactivate the motors, a twin-blade electromechanical contact is used to open and close the electrical circuit. The result is an amazing system for powering the movement, based on an exciting combination of the latest in solar technology and century old electromechanical know-how.

Jean-François Ruchonnet, working with Marc Alfieri, placed his spectacular vertical Cabestan movement in the center of the timepiece. Perfectly balanced at 12 oʼclock and 6 oʼclock, he added two solar panels mounted in metal frames held in place by cleverly designed pivots. The micromotors and rechargeable lithium-ion batteries are positioned to be discretely visible underneath the solar cells. In the middle of the movement, the twin-blade contact and its glass casing, based on the designs of 19th century scientist Léon Foucault, is eminently visible. The complex mechanism that links the crown to the movement also includes a striking 30 mm long axle that traverses the movement in its width. Finally, the watchcase is inspired by Marc Alfieriʼs designs, but Jean-François Ruchonnet restyled it, giving it an elegantly curved shape, a single curved crystal, a lateral window at 9 oʼclock and a sapphire case back all designed to increase the visability of the incredible mechanism inside.

Eric Coudray had the task of working with Jean-François Ruchonnetʼs design and Marc Alfieriʼs solar energy system, to integrate the technologies used and make sure that Sol Invictus works perfectly. He started by creating an elaborate system that automatically detects when the barillet needs to be rewound. At the end of its power reserve, a magnet automatically moves next to the glass tube containing the twin blade contacts. The magnetic attraction closes the electrical circuit and starts the rewinding sequence. The energy delivered by the motor passes through a set of differential gears before rewinding the movement by acting upon the chain and fusée. Once finished, the magnet is moved away and the contact opens to stop the motor. A separate motor is used to set the time electro-mechanically. The multifunction crown is equipped with a releasable mechanism that enables the owner to rewind the watch both electromechanically and manually, and to set time electromechanically.

For 7000 years, the Sun has been at the center of telling time, but it has never before been harnessed to assure the perpetual functioning of a mechanical timepiece. Sol Invictus breaks with the norms of traditional watchmaking and pushes back the limits of the imagination: the combination of an ingenious idea and a spectacular movement that becomes reality. A work of mechanical art destined for the worldʼs most demanding collectors. The art of watchmaking pushed to the extreme. And a highly successful collaborative effort that is emblematic of the new generation of watchmakers.

Suggested retail price for titanium model is CHF 595,000. Each timepiece will be produced on demand using the materials and configuration desired by its future owner, making each piece unique.

Technical details

Indications
• Hours, minutes, seconds read from three engraved rotary drums
• Power reserve indicator on an engraved rotary drum
• Symbols of the sun used by ancient civilisations engraved on the barrel

Movement
• Fully mechanical movement calibre CAB EC 101 with Swiss anchor escapement
• Mechanical tourbillon mecanique regulated on 6 positions with constant torque provided by the chain and fusee system
• Frequency: 21 600 alt/h or 3 hz
• Breguet balance-spring; geneva stud
• 53 rubies
• Steel chain 160 mm long composed of 235 links and 156 rivets
• Winding and time setting controlled using the crown (manual and Electromechanical) or perpetual winding using the solar power system
• Vertical gear system and differential
• Grade 5 titanium case with lateral window (other materials on request)

Power system
• Miniature perpetual energy solar power system
• Twin solar cells developed using proprietary technology from lʼines (institut National de lʼenergie solaire)
• Automatic electromechanical switch with twin-blade contact activated by magnet
• Lithium-ion batteries
• Programmable controller /oscillator circuitry
• Two brushless DC micromotors for rewinding and time setting

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