Grand Seiko’s best-ever
mechanical movement

A high beat movement with an 80 hour power reserve

In 1998, the creation of the 9S mechanical movement opened a new chapter in the Grand Seiko story. In 2020, the sixtieth anniversary of the first Grand Seiko, the pages turned again with a new high beat mechanical caliber, 9SA5 which, in its design, technology and functionality represents an advance just as important as the first 9S. Nine years in development and deploying all the skills and experience that Grand Seiko has gained over the past 60 years, 9SA5 is the finest mechanical movement that Grand Seiko has ever created.
Speaking about the early days of the project, Caliber 9SA5’s designer, Hisashi Fujieda, recalled “Our aims were to achieve high accuracy and long-lasting performance, and to bring about a revolution in mechanical watches.”
Fujieda described the nine year process that started with the conception of this aim and lead to its realization.

Inspired by the bravery of those who went before

Fujieda was in charge of the design of the new hairspring for Caliber 9S65 and based his ideas around his past experience with this and other Grand Seiko mechanical movements, notably Calibers 9S85 and 9S86.
“Around 2009, when we developed Caliber 9S85, we started wanting to go further, to innovate,” Fujieda says. “The design ideology of constantly striving to develop technology and mechanisms ahead of their time had stayed with us from the Daini Seikosha days and we were always on the look-out to discover the building blocks needed to create a new mechanical movement that would capture the essence of Grand Seiko.” Fujieda's inspiration came from looking back at the drawings for Caliber 4520, the 10-beat movement in the manual winding 45GS that had been created in 1968. “Caliber 4520 had a gear train that was different from most designs of movements at that period,” Fujieda says. He saw that, even then, his predecessors had not simply emulated previous designs when creating Grand Seiko mechanical watches but had taken the risk of innovation, a realization that encouraged him to develop a pioneering spirit in his own design philosophy. “Looking at those drawings gave me confidence in what I was feeling; it was the push I needed to translate my thoughts into concrete actions.”
Fujieda and the other members of the Movement

Design Division set out to discover how they could make real, practical advances in the basic qualities of a mechanical watch. They conducted a preliminary but deep investigation as their first step toward that end. From 2009 to 2011, they focused their attention primarily on the underlying technology of the movement. Over the same period, Fujieda embarked on his own course of independent study and analysis of every aspect of mechanical watches, from the design and structure of their movements to their exterior and more. “I went beyond studying the functional design elements and devoted extra attention to the finer points of the movement, including its appearance,” Fujieda says. In 2015, the team was ready to proceed with a development project that encompassed the movement, the exterior components and the watch as a complete whole. It was an all-embracing, “from the ground up” development process.
“We took plenty of time to develop a solid understanding of the underlying elements. That was the key to our achievement of the absolute ideals we sought.” Fujieda’s determination to make a completely new movement, coupled with his team’s unflagging efforts in support of his vision, resulted in the creation of Caliber 9SA5, a Grand Seiko movement that is entirely worthy of the 60th anniversary and one that opens a new chapter in the Grand Seiko story.

The pairing of a new Dual Impulse Escapement and twin barrels results in improved performance.

Caliber 9SA5 has both a long power reserve (80 hours) and a high precision rate of +5 to -3 seconds per day. Two innovations make these advances possible. First, a new Dual Impulse Escapement dramatically improves the efficiency of the driving force transmitted to the balance. Second, the use of twin barrels enables the mainspring to store more energy and extend the power reserve. The pairing of these innovations results in consistent accuracy and a power reserve that is 45% longer than that of the existing Grand Seiko high beat Caliber 9S8 series.
Fujieda dedicated the greater part of his energy to developing the Dual Impulse Escapement. An escapement comprises an escape wheel and a pallet fork and is the critical component of a mechanical watch as it and the balance determine the accuracy of the watch. The escapement of the conventional 9S movement uses reciprocal motion to deliver impulses indirectly from the escape wheel to the balance through the pallet fork. In contrast, the Dual Impulse Escapement of Caliber 9SA5 delivers the impulses in the conventional way in one direction of the reciprocal motion, but bypasses the pallet fork in the other direction, delivering the impulses directly from the escape wheel to the balance. Thus, the Dual Impulse Escapement transfers energy from the mainspring to the balance more efficiently.
Back in 2011, the team had first used Micro Electro Mechanical System, MEMS, a technology for the manufacture of high precision, lightweight parts and this system has long proven its worth in Grand Seiko’s mechanical movements, being used successfully for the pallet fork and the escape wheel in all 9S movements.

The twin barrels

MEMS was again central to the creation of the escapement of Caliber 9SA5. The team designed numerous escapements, analyzing and testing them while changing conditions such as the number of teeth on the escape wheels. They finally discovered that the Dual Impulse Escapement structure enabled them to achieve greater efficiency than any conventional escapement. The design of the escape wheel with a single layer of teeth keeps its moment of inertia low while enabling the direct transfer of impulses to the balance, but there are still just two pallets on the pallet fork as with previous 9S movements. “The simplicity of the new design made the entire movement lighter, resulting in roughly 20% greater efficiency than in the Caliber 9S8 series,” Fujieda says. “It is no exaggeration to say that the new structure was the key to achieving a long power reserve with a 10-beat movement.”
Generally, the higher the frequency of the balance, the heavier the balance and pallet fork and conventional wisdom dictates that, with the additional weight, the escape wheel and the pallet fork cannot catch up with the balance and the transmission efficiency decreases as the transmission power decreases. With the use of MEMS technology, it was possible to make a high precision, lightweight escape wheel and pallet fork for Caliber 9SA5 that delivers high efficiency and consistent operation.
The twin barrels secure all the energy needed to move the large balance, delivering more consistent accuracy than a conventional balance with a high moment of inertia. The team also re-designed the structure of the gear train so that fewer wheels are on the same layer as the barrels. This makes best use of the available space.

Dual Impulse Escapement

The overcoil and the Grand Seiko Free-sprung Balance

The team designed anew the other Caliber 9SA5 component that plays a critical role in determining the accuracy of a mechanical watch, the hairspring. To determine its optimum shape, they established a new analytical technique for predicting accuracy that enabled them to test over 80,000 different designs in search of the optimal shape before they arrived at the distinctive overcoil. Fujieda explained the importance of creating this new analytical technique for accurately predicting the accuracy of the hairspring from its shape. “It was impossible to use the existing theory on the ideal shape of hairsprings to make predictions about the impact of minuscule differences in their shapes. It took two years of trial and error to finally establish the new analytical technique, and only then did the search for the ideal hairspring shape start in earnest.”

Fujieda was determined to explore every possibility, no matter how unlikely some may have seemed. In search of the optimal shape for maximum accuracy, he studied every type and shape of spring in order to fully understand their performance characteristics before finally deciding upon this distinctive overcoil shape. Attention then turned to the balance. Caliber 9SA5 features a free-sprung balance that does not have a regulator to control the pace of the watch. “The lack of a regulator makes the entire watch more durable because its accuracy is less likely to suffer due to it being dropped or subjected to other impact,” Fujieda explained. Removing the regulator might have made it more difficult to adjust the isochronism, but Fujieda’s analysis revealed the principle that, under specific circumstances, the isochronism can be changed by rotating the stud that anchors the terminal of the hairspring. “Applying this principle to the structure we used gave us the ability to adjust the isochronism despite the lack of a regulator in the free-sprung balance.”

Grand Seiko Free-sprung Balance

The decisions to use the overcoil and Grand Seiko Free-sprung Balance presented challenges in the manufacture, assembly and adjustment of the components, but solutions were soon found in the skill and experience of the Grand Seiko team. Engineers were appointed to develop new jigs for shaping the outer terminal of the hairspring and adjusting the moment of inertia of the balance wheel. The entire arsenal of advanced manufacturing technology as well as the assembling and adjusting skills of the craftsmen and women of the Grand Seiko Studio Shizukuishi were deployed to overcome these challenges.

A slimmer profile and lower center of gravity

Although Caliber 9SA5 delivers enhanced functionality, it is 1mm, or 15%, slimmer than Caliber 9S85, thanks to the innovative horizontal layout of the barrels and gear trains.
The slimmer movement allowed the team to reduce the thickness of the watch case, making it very comfortable on the wrist. They also positioned the crown lower in the case to allow the watch to sit more easily.

“The position of the crown changes the center of gravity of the watch,” Fujieda explained. “The nearer the center of gravity to the wrist, the more secure the watch feels when it is worn.” Fujieda measured the distance from the bottom surface of the movement to the center of the crown to find the optimal crown position, and discovered it to be 45% to 50% of the thickness of the entire watch. “We achieved that enhanced comfort and feeling of stability by positioning the crown as close to the case back as possible, lowering the center of gravity of the watch.” Ingenuity even went into the way the Caliber 9SA5 crown feels when it is wound. It has the same solid and responsive feel as a manual winding watch. “We used MEMS technology to develop a new shape sliding wheel spring with a frame,” Fujieda says. “We attached it to the winding mechanism to make the automatic movement feel just like a manual winding watch.”

Creating elegance with inspiration from the scenery of Shizukuishi

The Caliber 9SA5 design team put their creativity to the test to make the movement as aesthetically pleasing as it was technically advanced. The design of the bridge is immediately striking. It has a gently curving outline that is inspired by the shape of Mt. Iwate and a bend in the nearby Shizukuishi River that runs past the Grand Seiko Studio Shizukuishi where the watch is made. “I was involved in the design from the conceptual stage and devoted energy to figuring out how to most elegantly position the components,” Fujieda recalled. The decision to use a flat bridge reduced the gap between it and the oscillating weight. “The most challenging part was fitting all those components into the small amount of space allotted by the flat bridge.”

Craftsmanship played a vital role in the finishing of the movement. The utmost attention to detail went into designing the movement and its finish so as to create the subtle brilliance that is at the heart of the Grand Seiko aesthetic. Fujieda was particularly concerned with softening the overall impression created by the play of light over the movement. The matte finish sides of the movement mute the light while the faceted ridge lines and edges of the bridge and the sides of the screw holes create a sparkling light that changes with the viewing angle, bestowing Caliber 9SA5 with the Japanese sense of beauty that the Grand Seiko Style requires. Furthermore, widening the bridge partition eliminates the strong effect of shadows, lending depth to the gradation between light and dark.

The surface of the bridge is graced by an undulating wave pattern modeled on the ripples of the water on the Shizukuishi River and the top surfaces of the wheels are individually finished with delicate patterns, revealing the depth of the craftsmanship that lies within every 9SA5 movement.
Fujieda and the design team worked on each aspect of every single step of the watchmaking process, from designing to manufacturing, assembling and adjusting the components and making the complete watch. “There is value in expending that kind of effort, the same value that lies in achieving accuracy and practicality, and in pursuing the beauty of the watch,” Fujieda says.
“I believe that value is conveyed beyond the bounds of time from the wearer of the watch to others, and I intend to continue pressing forward on the strength of that belief.”
Caliber 9SA5 is the result of the persistent spirit of inquiry and exploration exhibited by Fujieda and the other talented engineers at the Grand Seiko Shizukuishi Studio. With its innovation and its craftsmanship, this new movement points the way forward towards the future of Grand Seiko.

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