9R Spring Drive

Spring Drive is a unique watch technology. It generates energy like every other luxury mechanical watch but combines this with an electronic regulator to deliver a level of precision that no mechanical watch can match.

The development of Spring Drive was possible because Grand Seiko is one of the very few manufacturers with mastery of both electronic and mechanical watchmaking.

MECHANISM

Bringing together mechanical
and electronic watchmaking for the best of both worlds.

The two key elements behind the function of any watch are its power source and its time control system.

Spring Drive is a unique movement that combines the high torque of a mechanical watch with the high precision integrated circuit (IC) control system of an electronic watch.

Power source Control system
Mechanical watch Mainspring
High torque
(motive force driving the watch)
The wound-up mainspring exerts force to turn gears at a set speed as it unwinds, while the speed control and escapement mechanism consisting of the balance, pallet, and escape wheel govern overall precision. While precise. even the most accurate Grand Seiko models cannot compete with the accuracy of a quartz watch, with a daily rate of +8/-1 seconds.
Quartz watch Battery
Lower torque compared to
a mechanical watch
The battery sends electricity to a quartz oscillator, whose precise vibrations are detected by an integrated circuit (IC). The IC then moves the gears forward by exactly one second. The precision control of the IC allows for a high standard of accuracy, with Grand Seiko quartz models achieving a yearly rate of ±10 seconds.

MECHANISM

Powered by the mainspring

Spring Drive is powered by a mainspring, just like all other mechanical watches. This traditional way of generating power allows the watch to be entirely autonomous, with no need for a battery or other power source.

Winding the mainspring by turning the crown or by moving the wrist stores energy which is then transferred to gears and used to move the watch hands as the spring unwinds over time.

By taking advantage of the high level of torque afforded by the mainspring, the caliber needs no other power to move the long, wide hands in the smooth glide motion that is Spring Drive’s signature.

MECHANISM

Tri-Synchro Regulator

The core challenge for the team in the development of Spring Drive was energy generation and management. The solution lay in the creation of the Tri-Synchro Regulator, a device that generates a tiny electrical pulse from the motion of the mainspring and converts it into the power needed to activate a crystal oscillator and an electronic brake. The oscillator transmits a precise reference signal to the IC which applies a magnetic brake to maintain the revolution speed of a glide wheel at exactly eight revolutions a second. This precision is transferred through a gear train to the hands which display the time to a precision of ±1 second per day.

As its name suggests, the Tri-synchro Regulator uses three types of energy to regulate the moving parts and establish synchronicity:

  1. Mechanical power, from the mainspring
  2. Electrical power, creating a reference signaling via an IC/quartz oscillator
  3. Electromagnetic power, to apply a brake via a rotor/stator.

These three forces work in harmony to regulate the way the spring unwinds and to make possible the precise movement of the second hand.

TRI-SYNCHRO REGULATOR
1. MECHANICAL POWER

Generating electrical power from the unwinding mainspring

Spring Drive uses a system identical to that of a pedal-powered bicycle light to generate electrical power. A rotor connected to the end of the gear train acts together with a stator wound by wire to generate power. In a Spring Drive watch, the rotor, or glide wheel, makes eight full revolutions every second, generating a slight electric current.

TRI-SYNCHRO REGULATOR
2. ELECTRICAL POWER

Transmitting a precise signal through a quartz crystal oscillator

The electrical power generated by the glide wheel is used to activate a quartz oscillator and IC.
The quartz oscillator vibrates at exactly 32,768 Hz, transmitting a precise reference signal to the IC.

TRI-SYNCHRO REGULATOR
3. ELECTROMAGNETIC POWER

Applying the brake to control speed

The IC compares the reference signal from the quartz oscillator with the revolution speed of the glide wheel, and intermittently applies a magnetic brake when it detects that the glide wheel is operating too fast. This regulation of the glide wheel is transmitted to the gear train, ensuring that the watch hands move with precision.

CRAFTSMANSHIP

Master craftsmanship in assembly and adjustment

Spring Drive combines the best elements of both mechanical and electronic watches. While three-hand versions have over 200 components, versions with more functions, such as the Spring Drive chronograph have well over 300, all of which are assembled by hand.

The application of lubricating oils ensures the smooth interaction of all the components and there are no fewer than 80 lubrication points in the three hand caliber and 140 in the chronograph. The oils are applied by hand and both time and great skill are required to ensure that that the oils are applied with precision.

Design plans are based on tolerances down to the one hundred of a millimeter. The final adjustments and refinement of the components are completed by hand, because no machine can match the skills of our craftsmen and women – watchmakers whose superior craft gives rise to the extreme precision of Spring Drive.

TECHNOLOGY

A seconds hand that moves in glide motion

Because all the motion within a Spring Drive movement is in one direction, the seconds hand moves in glide motion. Just like time itself, the seconds hand moves continuously and silently with no tick or shudder and the beautiful, natural ow of time is expressed in every movement that it marks.

TECHNOLOGY

Bigger and bolder watch hands

While quartz movements benefit from high precision, their lack of torque makes moving thicker watch hands impossible.

In contrast, mechanical movements enjoy higher torque allowing for larger hands that reach right to the edge of the dial, but cannot match the level of precision of their quartz counterparts.

Spring Drive combines the precision of a quartz watch with the torque of a mechanical watch, to make possible a watch with both the long hands and the high precision that Grand Seiko demands.

TECHNOLOGY

The most accurate spring-driven chronograph in history

Thanks to the glide motion of the chronograph second hand, the Spring Drive Chronograph measures elapsed time exactly and not just to the nearest part of a second. With column wheel and vertical clutch systems for exact button operation, the Spring Drive Chronograph times up to 12 hours, with a precision of one second a day.

History

In 1977, Yoshukazu Akahane, a young watch engineer, decided to attempt the seemingly impossible, the creation of an ‘everlasting’ watch. His aim was a traditional watch, powered by a mainspring, that would deliver the one-second-a-day precision of which the company’s electronic watches were already capable. 28 years and 600 prototypes later, he realised his dream and Spring Drive was presented to the world. In 2007, and in the spirit of Akahane’s relentless pursuit of perfection, the Grand Seiko Spring Drive chronograph was born.

More

Movement Comparison

Movement Accuracy Power reserve Number of jewels Features
Spring Drive 5 Days
Caliber 9RA2
(Automatic with manual winding)
±10 seconds per month (±0.5 second per day) Approximately 120 hours (5 days) 38 jewels -Offset Magic Lever
-Dual-size Barrels
-One-piece Center Bridge
-Power reserve indicator
Spring Drive 5 Days
Caliber 9RA5
(Automatic with manual winding)
±10 seconds per month (±0.5 second per day) Approximately 120 hours (5 days) 38 jewels -Offset Magic Lever
-Dual-size Barrels
-One-piece Center Bridge
-Power reserve indicator
Manual-winding 8-Day Power Reserve Spring Drive
Caliber 9R01
(Manual winding)
±0.5 seconds per day (±10 seconds per month) Approximately 192 hours 56 jewels -Power reserve indicator
-Quick correction function of time difference
Manual-winding Spring Drive
Caliber 9R02
(Manual winding)
±1 second per day (±15 seconds per month) Approximately 84 hours 39 jewels -Torque Return System
-Dual-Spring Barrel
-Power reserve indicator
AUTOMATIC SPRING DRIVE 3-DAY CHRONOGRAPH GMT
Caliber 9R96
(Automatic with manual winding)
±0.5 second per day (±10 seconds per month) Approximately 72 hours 50 jewels -Power reserve indicator
-Dual time function with 24-hour hand
-Quick correction function of time difference adjusting to a calendar
-Stopwatch function
Automatic Spring Drive 3-Day Chronograph GMT
Caliber 9R86
(Automatic with manual winding)
±1 second per day (±15 seconds per month) Approximately 72 hours 50 jewels -Power reserve indicator
-Dual time function with 24-hour hand
-Quick correction function of time difference adjusting to a calendar
-Stopwatch function
Automatic Spring Drive 3-Day GMT
Caliber 9R66
(Automatic with manual winding)
±1 second per day (±15 seconds per month) Approximately 72 hours 30 jewels -Power reserve indicator
-Dual time function with 24-hour hand
-Quick correction function of time difference adjusting to a calendar
Automatic Spring Drive 3-Day
Caliber 9R65
(Automatic with manual winding)
±1 second per day (±15 seconds per month) Approximately 72 hours 30 jewels -Power reserve indicator
-Date display
Manual-winding Spring Drive
Caliber 9R16
(Automatic with manual winding)
±0.5 second per day (±10 seconds per month) Approximately 72 hours 30 jewels -Power reserve indicator
-Dual time function with 24-hour hand
-Quick correction function of time difference adjusting to a calendar
Manual-winding Spring Drive
Caliber 9R31
(Manual winding)
±15 seconds per month(±1 second per day) Approximately 72 hours 30 jewels -Dual-Spring Barrel
-Power reserve indicator
Automatic Spring Drive 3-Day
Caliber 9R15
(Automatic with manual winding)
±0.5 second per day (±10 seconds per month) Approximately 72 hours 30 jewels -Power reserve indicator