The Grand Seiko Kodo Constant-force Tourbillon
The Grand Seiko Kodo Constant-force Tourbillon is Grand Seiko’s first mechanical complication watch. At its heart is a uniquely innovative movement, Caliber 9ST1, which, for the very first time in horological history, combines a tourbillon and a constant-force mechanism as one unit on a single axis.
The watch is named Kodo, or ‘heartbeat’ in Japanese, after the unique motion of the two mechanisms and the sound of the rhythm it makes. The inner tourbillon carriage rotates smoothly as the balance steadily vibrates at 8-beats per second, and the outer constant-force carriage follows its rotation at exact one-second intervals to create a 16th note rhythmic feel.
The components are painstakingly finished by hand using a variety of techniques to endow the overall movement with the quiet yet enduring sparkle that is the hallmark of Grand Seiko. The case is constructed of both Platinum 950 and Grand Seiko’s Brilliant Hard Titanium to achieve a long-lasting beauty.
The award was accepted by Akio Naito (right), President of Seiko Watch Corporation, and Grand Seiko’s movement designer Takuma Kawauchiya (left), who designed and assembled the winning watch. In accepting the award, Akio Naito said, “Everyone at Grand Seiko is incredibly proud of this honor tonight, as Kodo is the first mechanical complication watch from the brand in its 62-year history. I would like to express my sincere gratitude to the members of the jury who recognized this achievement by a team of our engineers and watchmakers, led by Takuma Kawauchiya”
The integration of the two mechanisms
Caliber 9ST1 is complex in its engineering and design but is based on the simple insight that the integration of a constant-force mechanism and a tourbillon as one unit on a single axis would deliver practical benefits. Because there are no wheels or other components between the two mechanisms, there is no loss or change in the torque transmitted from the constant-force mechanism to the balance wheel. This leads to an increased duration of 50 hours for the constant-force mechanism and a more stable amplitude of the balance. Together, these characteristics deliver the very stable accuracy of the movement. In addition, and crucially for Grand Seiko, the volume of the movement could be reduced, allowing the aesthetics of Grand Seiko to be respected and the watch to be eminently wearable and perfectly comfortable on the wrist.
Innovation in precision, beauty and sound
The integration of the two mechanisms creates a dazzling visual effect. The inner tourbillon carriage rotates smoothly as the balance steadily vibrates at eight beats per second and the outer constant-force carriage follows its rotation at exact one-second intervals. The sounds of the escapement and of the once-per-second impulse of the constant-force mechanism harmonize with this regular visual rhythm to create, for both the eye and the ear, a deeply satisfying and re-assuring heartbeat. There is a powerful yet gentle charm to the sound that is set to a 16th note or semi-quaver which is made possible by 9ST1 being the movement with the highest frequency* ever to incorporate a constant-force mechanism.
*As of February 2022, based on Grand Seiko’s research.
The integration of the two mechanisms
Caliber 9ST1 is complex in its engineering and design but is based on the simple insight that the integration of a constant-force mechanism and a tourbillon as one unit on a single axis would deliver practical benefits. Because there are no wheels or other components between the two mechanisms, there is no loss or change in the torque transmitted from the constant-force mechanism to the balance wheel. This leads to an increased duration of 50 hours for the constant-force mechanism and a more stable amplitude of the balance. Together, these characteristics deliver the very stable accuracy of the movement. In addition, and crucially for Grand Seiko, the volume of the movement could be reduced, allowing the aesthetics of Grand Seiko to be respected and the watch to be eminently wearable and perfectly comfortable on the wrist.
Innovation in precision, beauty and sound
The integration of the two mechanisms creates a dazzling visual effect. The inner tourbillon carriage rotates smoothly as the balance steadily vibrates at eight beats per second and the outer constant-force carriage follows its rotation at exact one-second intervals. The sounds of the escapement and of the once-per-second impulse of the constant-force mechanism harmonize with this regular visual rhythm to create, for both the eye and the ear, a deeply satisfying and re-assuring heartbeat. There is a powerful yet gentle charm to the sound that is set to a 16th note or semi-quaver which is made possible by 9ST1 being the movement with the highest frequency* ever to incorporate a constant-force mechanism.
*As of February 2022, based on Grand Seiko’s research.
Two materials in perfect harmony
The case is constructed from both Platinum 950 and Grand Seiko’s Brilliant Hard Titanium to achieve a long-lasting beauty. Some case parts of both materials are mirror polished and others have a hairline finish; both processes are completed by hand by highly skilled craftsmen and women to ensure that, from every angle, a visually pleasing harmony is revealed. The two case materials combine most evidently at the tapered end of the lugs where a small open space between each lug adds a lightness and unique aspect to the overall design.
Light, shadow and space
breathe within the case and there is sufficient space for light to penetrate, through both the front and back of the case, revealing the beauty of the hand finishing. For the same reason, the delicate interplay of light and shadow that is central to the Grand Seiko aesthetic is there to be enjoyed in the subtle shade gradations, angles and textures. Each major component is painstakingly finished by hand using a variety of techniques to endow the overall movement with the quiet yet enduring sparkle that is the hallmark of Grand Seiko.
Two materials in perfect harmony
The case is constructed from both Platinum 950 and Grand Seiko’s Brilliant Hard Titanium to achieve a long-lasting beauty. Some case parts of both materials are mirror polished and others have a hairline finish; both processes are completed by hand by highly skilled craftsmen and women to ensure that, from every angle, a visually pleasing harmony is revealed. The two case materials combine most evidently at the tapered end of the lugs where a small open space between each lug adds a lightness and unique aspect to the overall design.
Light, shadow and space
breathe within the case and there is sufficient space for light to penetrate, through both the front and back of the case, revealing the beauty of the hand finishing. For the same reason, the delicate interplay of light and shadow that is central to the Grand Seiko aesthetic is there to be enjoyed in the subtle shade gradations, angles and textures. Each major component is painstakingly finished by hand using a variety of techniques to endow the overall movement with the quiet yet enduring sparkle that is the hallmark of Grand Seiko.
