Grand Seiko Spring Drive
In 1977, a young engineer at Seiko by the name of Yoshikazu Akahane had a dream. This dream was to have the perfect, everlasting watch. A watch with the aesthetic beauty and craftsmanship of a mechanical, but the accuracy of quartz. This dream lead to an over 28 year mission that included over 600 prototypes, 230 patents and a relentless dedication to perfecting his dream.
The concept for the Grand Seiko Spring Drive was born with the idea of a bicycle coasting down a hill, using a brake to slow its speed. Akahane envisioned this concept in the regulating mechanism for Spring Drive. Solely powered by a mainspring, using no battery or motor, the regulating of the mainsprings unwinding would be magnetically controlled compared to the traditional rapid rocking back and forth of a balance wheel. The balance wheel rocking back and forth is reliant on the hairspring, which is very sensitive and easily affected by shock, magnetism and temperature. In Spring Drive, as the mainspring unwinds, it will power the gear train moving the hands as in a traditional mechanical. Instead of providing energy to the escapement (balance wheel, hairspring, escapement gear and pallet fork), the energy goes to a series of speed increasing wheels and a rotor (glide wheel). As this rotor turns from the unwinding of the mainspring, it generates electricity through an ultra precisely wound coil (that helps eliminate power loss), providing electricity to power a quartz oscillator and IC. Only 25 nano-watts of electricity are used to power these two items. The IC regulates the speed of the rotor by applying and releasing an electro-magnetic brake and compares the accuracy of the electric signals from the crystal oscillator and the spinning speed of the rotor (glide wheel), therefore the speed of the unwinding of the mainspring. This regulating mechanism is known as the Tri-Synchro Regulator. In turn, Spring Drive achieves quartz like accuracy of only +/- 15 seconds per month, and because the gliding wheel only rotates in one direction, it is a continuous and smooth motion, but also alleviates the friction and collision found in a traditional mechanical. This is reflected in the gliding motion of the second hand as well as extended service intervals.
Grand Seiko received its first Spring Drive caliber in 2004 under the label 9R. Today, the 9R calibers are expressed in the 3 hand 9R65 with 276 parts and 30 jewels, the GMT 9R66 with 296 parts and 30 jewels, and Chronograph GMT 9R86 with 416 parts and 50 jewels. All of these pieces feature a faster and more efficient winding system called the "Magic Lever" (introduced by Seiko in 1959) and Seiko's proprietary Spron 510 mainspring alloy which gives these pieces a 72 hour power reserve, even on the chronograph variant 9R86 when the chronograph is in use. The 9R86 also uses a vertical clutch and column wheel for optimal performance of the stopwatch feature. These elaborate calibers are manufactured and hand assembled at Shinshu Watch Studio in Shiojiri, in the Nagano prefecture of central Japan. The Grand Seiko Spring Drive is one of the best of all possible worlds.