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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Grand Seiko Spring Drive is powered by a wound mainspring, but it uses a quartz oscillator and electronic control to regulate the movement. The mainspring supplies the energy; a quartz timing reference and electromagnetic brake govern its rate. That hybrid arrangement is why the seconds hand glides continuously instead of ticking.
How does Grand Seiko Spring Drive work?
The mechanism combines a conventional mechanical energy source with electronic timekeeping and electromagnetic regulation. Grand Seiko’s official explanation describes the process this way:
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- The mainspring stores and supplies energy. Winding the crown or the automatic oscillating weight winds the mainspring. As it unwinds, it drives the gear train and hands, and turns the glide wheel. Grand Seiko says the mainspring is Spring Drive’s power source; the movement has no battery or separate motor.
- The glide wheel generates electricity. A coil around the glide wheel converts its rotation into a small electrical current. That current powers the integrated circuit (IC) and quartz oscillator.
- The quartz oscillator provides a timing reference. The oscillator vibrates at 32,768 Hz. The IC compares its reference signal with the glide wheel’s rotation.
- An electromagnetic brake regulates the wheel. When needed, the IC applies the brake to control the glide wheel’s speed. That regulation passes through the gear train to the hands.
In short, Spring Drive is mainspring-powered and electronically regulated. The mechanical train transfers the mainspring’s energy, while quartz timing and the IC help control the rate. Grand Seiko’s Spring Drive overview describes the seconds hand as moving in a “uniquely smooth and silent glide motion.”
Is Spring Drive mechanical or quartz?
It has elements of both, so either label alone is incomplete. Spring Drive gets its energy from a mechanical mainspring and uses a gear train to move the hands. But it does not rely on a traditional balance wheel and escapement to regulate time: a quartz oscillator, IC and electromagnetic brake regulate the glide wheel instead. It is not battery-powered; Grand Seiko’s 9R65 instruction manual states, “No motor or battery is mounted.”
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- Three-fold clasp with push button release
- Dual-curved sapphire crystal
- Power reserve display on the back
- Power resrve Approx. 72 hours(3 days)
The distinction is useful when comparing watch types: the power source tells you where the energy comes from, while the regulator tells you how the movement controls its rate. In Spring Drive, those roles are handled by different parts of the same system. Grand Seiko notes that movement construction and components can differ by caliber, so details should not be assumed to be identical across every 9R movement.
Why does the Spring Drive seconds hand glide?
The electromagnetic regulation controls the glide wheel’s rotation continuously rather than advancing the hands in discrete ticks. Because the gear train transfers that steady motion to the hands, the seconds hand appears to sweep smoothly around the dial. The continuous glide is a result of how the movement is regulated, not a separate motor driving the hand.
How do the 9R65 and 9RB2 compare?
The 9R65 and 9RB2 illustrate two different published accuracy specifications within Grand Seiko’s Spring Drive range. The figures below are manufacturer specifications, not independent test results.
| Movement | Grand Seiko stated accuracy | Approximate power reserve | Winding and distinguishing details |
|---|---|---|---|
| 9R65 | ±15 seconds per month (±1 second per day), according to Grand Seiko’s current specification page; no publication year is displayed. | 72 hours, according to Grand Seiko’s current specification page; no publication year is displayed. | Self-winding with manual winding; date, power-reserve indicator and hacking. Grand Seiko calls it its “most standard” 9R movement. |
| 9RB2 U.F.A. | ±20 seconds per year (approximately ±3 seconds per month). Grand Seiko says its comparison is based on its research as of April 2025. | 72 hours, according to Grand Seiko’s current specification page; no publication year is displayed. | Self-winding with manual winding; temperature-compensating IC, vacuum-sealed oscillator package and a regulation switch for after-sales adjustment. |
| 9RA family | No matched accuracy figure is stated in the cited Grand Seiko pages. | Approximately five days, according to Grand Seiko’s current Evolution 9 explainer; no publication year is displayed. | Grand Seiko describes Dual-size Barrels and temperature correction as design features. |
9R65: the established 72-hour example
Grand Seiko specifies the 9R65 as self-winding with manual winding, with approximately 72 hours of reserve and accuracy of ±15 seconds per month (±1 second per day). Its U.S. caliber page lists the SBGA211 among the models using this movement. See Grand Seiko’s 9R65 specifications and model list; listed models and prices may vary by market and over time.
9RB2 U.F.A.: a tighter published accuracy specification
Grand Seiko specifies the 9RB2 U.F.A. at ±20 seconds per year, or approximately ±3 seconds per month, with approximately 72 hours of reserve. The annual-accuracy comparison is qualified by the brand as based on its research as of April 2025. Its 9RB2 caliber page describes a temperature-compensating IC and a vacuum-sealed oscillator package. These are published brand specifications, not a claim about results from independent testing.
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Grand Seiko introduced the U.F.A. designation in an announcement dated April 1, 2025, describing it as a new era in the brand’s Spring Drive history. Read the dated announcement.
9RA: a longer-reserve branch
The 9RA2 and 9RA5 extend the range in a different direction: Grand Seiko describes them as five-day Spring Drive movements. The brand identifies Dual-size Barrels and temperature correction as features of the family. Grand Seiko’s Evolution 9 explainer discusses the 9RA family and the five-day reserve.
The figures above do not establish equivalent case dimensions, finishing, servicing needs or wearing performance across the calibers. They are a comparison of the specific attributes Grand Seiko publishes for these movements.
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Where Spring Drive comes from
Grand Seiko says development took more than 20 years from initial conception to completion, and that the 9R Spring Drive was introduced in 2004. The company says the movements are manufactured and hand-assembled at Shinshu Watch Studio in Shiojiri, Nagano Prefecture. Its historical overview traces later developments including a chronograph, the Micro Artist Studio 9R01 and 9R02, the five-day 9RA2 and 9RA5, and the 9RB2 U.F.A. introduced in 2025. Grand Seiko’s Spring Drive history provides the brand’s account of that development.
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