Complex timepieces that rotate massive bodies are the result of advancements in design and manufacturing technology. Examples include Piaget's "Relatif" and Cartier's "Mystérieuse." The ultimate example is the "Astronomia Regulator," unveiled in 2024. Its mechanism, in which the axis carrying the hours, minutes, and tourbillon, along with the seconds disc, rotates once per minute, is unprecedented.
Since the 2000s, many watchmakers have dreamed of creating complex timepieces that rotate heavy components at high speeds. This timepiece represents the pinnacle of that dream. A 1/6 second constant force mechanism ensures that the heavy regulator and seconds disc rotate once per minute. Manual winding (Cal. JCAM56). 21,600 vibrations per hour. Power reserve of approximately 48 hours. 18K rose gold case (43mm diameter, 18mm thickness). 30m water resistance. Limited edition of 99 pieces worldwide. Price upon inquiry.
Photographs by Eiichi Okuyama
Masamasa Hirota (this magazine), Yukiya Suzuki (this magazine): Interview and text
Text by Masayuki Hirota (Chronos-Japan)
Text & Edited by Yukiya Suzuki (Chronos-Japan)
Edited by Yuto Hosoda (Chronos-Japan)
[Article published in the July 2025 issue of Kronos Japan]
A pinnacle achievement in 21st-century watchmaking technology
Jacob & Co.'s Astronomia, unveiled in 2014, was a remarkably original and indomitable timepiece. After all, four arms protruded from a central axis that rotated once clockwise every 10 minutes, further rotating the hour and minute dials, the tourbillon, and the two spheres.
Initially, the project was spearheaded by independent watchmaker Luca Soprana. The patent for the watch (Swiss Patent 710811), obtained by Jacob & Co. on December 30, 1920, lists Jacob & Co. as the applicant and Luca Soprana as the inventor. The same applies to the twin-axis tourbillon featured in the first Astronomia (Swiss Patent 710836). However, mass production of this watch was impossible in Soprana's small workshop. In contrast, Jacob & Co. chose Concept, a cutting-edge movement manufacturer, as a partner, and together they grew the Astronomia.
As many involved have noted, smoothly rotating a heavy rotating object is difficult in itself. Nevertheless, Jacob added various additional mechanisms to the Astronomia. Having overcome the challenge of weight, Jacob's next challenge was the speed of rotation. Current CEO Benjamin Arabo says that his father, Jacob Arabo, the founder and creator of Astronomia, told him to make the rotating object spin faster.
The completed "Astronomia Regulator" turned out to be an incredibly complex timepiece, with the axis supporting the hours, minutes, and tourbillon rotating once per minute (clockwise), and the seconds disc placed on the base of the movement also rotating once per minute (counterclockwise).
Approximately four years prior to this, Jacob had patented a concept (Swiss Patent 711613) for a mechanism that rotated a massive display unit mounted on the movement's base. This culminated in the "Fleur des Jardins," a watch with a jewel-encrusted mother-of-pearl dial that rotates once every 10 minutes. This is probably the heaviest rotating body Jacob has ever operated. With such strong torque, it would certainly not be impossible to rotate a massive seconds disc at high speed. However, even with strong torque, accurately controlling the seconds display is extremely difficult.
The solution was a new constant force mechanism developed by Concept (Swiss Patent 719508). This mechanism "allows the winding gear to be released each time the balance wheel changes, whereas conventionally the gear is released every second," and the constant force mechanism operates at a rate of one-sixth of a second. The aim is to apply a more stable force to the balance wheel, but the patent document also states that "this additional force between the mainspring and the constant force mechanism can therefore be used, for example, to rotate an animation." This is why the developers emphasized that "without the constant force mechanism that operates at one-sixth of a second, the Astronomia Regulator could not have been realized."
The Cal.JCAM56 uses two barrels to drive various mechanisms. While the mainspring torque is not publicly disclosed, it's certainly not small considering it rotates a massive mechanism quickly and also carries a 1/6-second constant force. Normally, precision ceramic bearings are used to reduce resistance. However, Jacob & Co. has consistently employed ordinary steel bearings. The reason is that "the play (in the bearings) becomes too large, preventing smooth rotation."
In addition, Jacob & Co. focused on reducing the weight of the rotating parts. The massive seconds disc is made of lightweight polycarbonate. Furthermore, titanium is used for certain components of the movement's rotating parts. One might expect that such a large rotating part would negatively affect accuracy, but it achieves a remarkable level of precision, within ±4 seconds even in the vertical direction.
Jacob & Co.'s "Astronomia Regulator" has overcome the difficult challenge of spinning a heavy rotating body as fast as possible. This is probably the ultimate form that the watch industry has reached today.
