Manual-winding Spring Drive
Caliber 9R02
The Cal. 9R02 is a manual-winding Spring Drive movement crafted by the Micro Artist Studio. The movement’s power reserve of approximately 84 hours is realized through its Dual-Spring Barrel and the unique Torque Return System.
The Dual-Spring Barrel achieves a greater power reserve by housing two long and thin mainsprings in a single barrel. This allows the movement to remain compact and to deliver greater power, all while avoiding the loss of energy efficiency that two barrels might involve. The two mainsprings unwind simultaneously, generating a high level of torque.
The Torque Return System is a unique mechanism that optimizes the high torque of Spring Drive to use energy more effectively and extend the power reserve. When the mainspring has been fully wound and the torque output is at its highest, a portion of its power is not needed to maintain precision and is in effect wasted in a normal movement. The Torque Return System uses this energy to rewind the mainspring, increasing the power reserve.
Specifications
| Winding mechanism | Manual winding |
|---|---|
| Accuracy | ±1 second per day (±15 seconds per month) |
| Power reserve | Approximately 84 hours |
| Number of jewels | 39 jewels |
| Features | -Torque Return System
-Dual-Spring Barrel -Power reserve indicator |
What makes 9R Spring Drive special?
Spring Drive, one of the great innovations in modern watch making history, regulates a spring-driven movement with state-of-the-art electronic technology that functions without batteries or other external power source. Its sole power source is a mainspring, which drives a series of gears. A rotor, connected to the end of these gears, generates a small electrical charge that activates an electronic circuit and quartz oscillator. Its accuracy is unprecedented for a watch wound by a mainspring. The development of the 9R Spring Drive movement was possible only because Grand Seiko is one of the few manufacturers with expertise in both mechanical and electronic watches.
