2A0B:5F04:5024:3700:4565:C377:7284:4352: /* Calibers */Added content (specified that the Calibre 9RB2's power reserve indicator is rear-facing, like Calibre 9RA2.

2025-05-04T13:08:44Z

Calibers: Added content (specified that the Calibre 9RB2's power reserve indicator is rear-facing, like Calibre 9RA2.

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{{Short description|Hybrid (mechanical and quartz) watch movement}}
[[File:Seiko Spacewalk.JPG|thumb|300px|The Seiko Spacewalk is a limited edition Spring Drive model, designed specifically for use in space]]
'''Spring Drive''' is a name given to a series of [[Movement (clockwork)|watch movements]] produced by [[Epson]] in [[Shiojiri, Nagano|Shiojiri]]. The concept of using a mainspring to power a quartz timing package was first conceived in 1977 by Yoshikazu Akahane (赤羽好和) at [[Suwa Seikosha]]<ref name=creator>{{cite web |url=https://www.japantimes.co.jp/news/2018/03/26/business/time-passes-beautifully-elegant-high-quality-watch/ |title=Time passes beautifully on elegant, high-quality watch |date=26 March 2018 |website=japantimes.co.jp |publisher=[[The Japan Times]] |access-date=11 April 2019}}</ref> (now a part of Epson after a 1985 merger).<ref name=epson-history>{{Citation | contribution-url = http://global.epson.com/company/corporate_history/milestone_products/35_spring_drive.html | contribution = Seiko/Credor Spring Drive | title = Milestone Products | publisher = Seiko Epson}}</ref> Specified to one second accuracy per day,<ref name = gs>{{cite web |url=https://www.grand-seiko.com/us-en/about/movement/springdrive |title=spring drive movement about |website=grand-seiko.com |publisher=[[Grand Seiko]] |access-date=11 April 2019}}</ref> the movement uses a conventional gear train as in traditional mechanical watches, but rather than an [[escapement]] and [[balance wheel]], instead features Seiko's ''Tri-synchro Regulator'' system in which power delivery to the watch hands is regulated based on a reference quartz signal.<ref name = gs />

Commercially released in 1999,<ref name=epson-history /> the movement is found in watches distributed by the [[Seiko|Seiko Watch Corporation]], including its '''Credor''', '''Grand Seiko''', '''Presage''', and '''Prospex''' brands.

==Mechanics==
The Spring Drive uses a conventional [[mainspring]]<ref name = gs /> and [[Barrel (horology)|barrel]]<ref name = gs-history>{{cite web |url=https://www.grand-seiko.com/us-en/about/history |title=HISTORY - ABOUT - Grand Seiko |website=grand-seiko.com |publisher=[[Grand Seiko]] |access-date=20 October 2019}}</ref> along with automatic and/or stem winding to store energy, just as in a mechanical watch.<ref name = gs /> However, the [[escapement]] and [[balance wheel]] in mechanical watches is replaced by Seiko's ''Tri-synchro Regulator'' system, a [[phase-locked loop]] wherein a rotor, which Seiko refers to as a "glide wheel", is powered by the mainspring barrel via a [[stator]]. The glide wheel in turn powers a reference quartz crystal and accompanying [[integrated circuit]] which controls an electromagnetic brake which then regulates the rotational speed of the glide wheel itself.<ref name = gs />

The glide wheel is intended to rotate eight times per second; the rotational speed is sampled once every rotation and a variable braking force is continuously applied to maintain that target frequency. As the glide wheel directly powers the seconds hand of the watch, this results in a true continuously sweeping second hand – in contrast to the beats per time motion resulting from the back-and-forth movement of traditional mechanical watches or the tick of typical quartz watches.<ref name = gs />

==History==
The design was first conceived by Yoshikazu Akahane at [[Seikosha|Suwa Seikosha]] in 1977<ref name=creator /> and [[patent]]s were applied for it in 1982;<ref name=epson-pdf>{{cite web |url=https://global.epson.com/company/corporate_history/milestone_products/pdf/35_spring-drive.pdf |title=Seiko/ Credor Spring Drive |website=global.epson.com |publisher=[[Seiko Epson]] |date=December 1999 |access-date=20 October 2019}}</ref> in total, no fewer than 230 patents have been applied worldwide for this movement.<ref>{{cite web |url=https://www.indiatoday.in/business/story/seiko-launches-limited-edition-watches-91692-2012-02-02 |title=Seiko launches limited edition watches |publisher=[[India Today]] |date=2 February 2012 |access-date=20 October 2019}}</ref> Initial development was hindered by the high energy consumption of the reference quartz crystal and integrated circuit<ref name=epson-pdf /> making a watch with a then-target 48-hour power reserve impossible;<ref name=bredan>{{cite web |url=https://www.ablogtowatch.com/history-seiko-spring-drive-movement/ |title=The Amazing History & Functionality Of The Seiko Spring Drive Movement |first=David |last=Bredan |date=5 February 2017 |access-date=20 October 2019}}</ref> another attempt in 1993 was also unsuccessful for the same reason.<ref name=epson-pdf /> It was not until a third attempt in 1997, using a quartz crystal and integrated circuit with energy consumption approximately one one-hundredth that used in the initial attempt in 1982,<ref name=bredan /> that a Spring Drive watch with sufficient power reserve was deemed feasible.<ref name=epson-pdf /> Over 600 prototypes were produced during development.<ref name=creator /><ref name = gs /><ref name=ssd>{{cite web |url=http://www.seikospringdrive.com/brochure/pdf/all.pdf |title=Seiko Spring Drive The Quiet Revolution |website=seikospringdrive.com |publisher=[[Seiko|Seiko Watch Corporation]] |access-date=20 October 2019}}</ref>

The Spring Drive movement was announced publicly in 1997 and presented at the 1998 [[BaselWorld|Basel Watch Fair]].<ref name=creator /><ref name=ssd/> In 1999, the first production models were made available in Japan as limited edition, manual-wind watches in both the '''Credor''' and '''Seiko''' brands.<ref name=epson-history /><ref name=epson-pdf /><ref name=ssd/> The first non-limited model was released in Japan in 2002.<ref name=epson-pdf />

The 1st spring drive automatic-wind movement of Grand Seiko was released in September 2004, the reference number is SBGA001.{{Citation needed|date=August 2023}}

The first [[automatic watch|automatic-wind]] Spring Drive model was released in 2005,<ref name=ssd/> and coincided with the introduction of the Spring Drive movement to markets outside of Japan.<ref name=ssd/>

==Calibers==
[[Image:Seiko Spring Drive 5R86 parts.jpg|thumb|right|200px|The parts of the 5R86 Spring Drive caliber]]
Established in 2000 within Seiko Epson's facility in Shiojiri, the Micro Artist Studio is responsible for the production of Spring Drive calibers that are particularly advanced in terms of technical and aesthetic craftsmanship. The studio manufactures movements used in Credor's complicated watches, such as the Sonnerie and Minute Repeater, as well as in the Grand Seiko Masterpiece Collection.<ref name="wc210624">{{cite web|url=https://www.webchronos.net/iconic/39405/|archive-url=https://web.archive.org/web/20241114185030/https://www.webchronos.net/iconic/39405/|script-title=ja:クレドール／マイクロアーティスト工房編|language=ja|publisher=web Chronos|date=21 June 2024|archive-date=14 November 2024|access-date=20 April 2025}}</ref><ref name="mic081124">{{cite web|url=https://www.grand-seiko.com/us-en/worldofgrandseiko/manufacture/microartiststudio|archive-url=https://web.archive.org/web/20241108051358/https://www.grand-seiko.com/us-en/worldofgrandseiko/manufacture/microartiststudio|title=The Micro Artist Studio|publisher=Seiko|date=|archive-date=8 November 2024}}</ref>

Early models, manual wind and 48h power reserve:

* '''7R68''' : 30 jewels, date.
* '''7R78''' : 30 jewels, date.
* '''7R88''' : 30 jewels, date.
* '''7R99''' : 32 jewels.

Current [[Caliber (horology)|calibers]] with standard features. Time accuracy: monthly rate within ±15 sec (equivalent to a daily rate of ±1 sec), and power reserve (72h) indicator. (Exceptions apply to some models.)

* '''5R64''' : 32 jewels, date, small seconds hand.
* '''5R65''' : 30 jewels, date.
* '''5R66''' : 30 jewels, date, GMT.
* '''5R67''' : 30 jewels, Moon Phase indicator.
* '''5R77''' : 30 jewels, Moon Phase indicator.
* '''5R85''' : 49 jewels, date, Chronograph, '''Izul'''.
* '''5R86''' : 50 jewels, date, GMT, Chronograph, '''Spacewalk'''.
* '''7R06''' : 88 jewels, manual winding, '''Sonnerie'''. (Produced by the Micro Artist Studio)<ref name="wc210624"/>
* '''7R08''' : 44 jewels, manual winding, '''Eichi I'''. (Produced by the Micro Artist Studio)<ref name="wc210624"/>
* '''7R11''' : 112 jewels, manual winding, '''Minute Repeater'''. (Produced by the Micro Artist Studio)<ref name="wc210624"/>
* '''7R14''' : 41 jewels, manual winding, '''Eichi II'''. (Produced by the Micro Artist Studio)<ref name="wc210624"/>
* '''9R01''' : 56 jewels, manual winding. Power reserve 8 days (192h). Monthly rate within ±10 sec (±0.5 sec per day).<ref name="gs9r">{{cite web|url=https://www.grand-seiko.com/us-en/collections/movement/springdrive|archive-url=https://web.archive.org/web/20250403122950/https://www.grand-seiko.com/us-en/collections/movement/springdrive|title=9R Spring Drive|publisher=Seiko|date=|archive-date=3 April 2025|access-date=3 April 2025}}</ref> (Produced by the Micro Artist Studio)<ref name="mic081124"/>
* '''9R02''' : 39 jewels, manual winding. Power reserve 84 hours.<ref name="gs9r"/> (Produced by the Micro Artist Studio)<ref name="mic081124"/>
* '''9R15''' : 30 jewels, date. Monthly rate within ±10 sec (±0.5 sec per day).<ref name="gs9r"/>
* '''9R16''' : 30 jewels, date. GMT. Monthly rate within ±10 sec (±0.5 sec per day).<ref name="gs9r"/>
* '''9R31''' : 30 jewels, manual wind.<ref name="gs9r"/>
* '''9R65''' : 30 jewels, date.<ref name="gs9r"/>
* '''9R66''' : 30 jewels, date, GMT.<ref name="gs9r"/>
* '''9R84''' : 41 jewels, date, Chronograph.<ref name="gs9r2">{{cite web|url=https://www.grand-seiko.com/instructions/html/GS_9R_ja/AGFISYjlvuuait|archive-url=https://web.archive.org/web/20230112234339/https://www.grand-seiko.com/instructions/html/GS_9R_ja/AGFISYjlvuuait|title=製品仕様（ムーブメント）|publisher=Seiko|date=|archive-date=12 January 2023|access-date=3 April 2025}}</ref>
* '''9R86''' : 50 jewels, date, GMT, Chronograph.<ref name="gs9r"/>
* '''9R96''' : 50 jewels, date, GMT, Chronograph. Monthly rate within ±10 sec (±0.5 sec per day).<ref name="gs9r"/>

Current calibers with higher power reserve and higher accuracy. Time accuracy: monthly rate within ±10 sec (equivalent to a daily rate of ±0.5 sec) and power reserve (5 days) indicator.<ref name="gs9r"/>

* '''9RA5''' : 38 jewels, date.
* '''9RA2''' : 38 jewels, date. Rear power reserve indicator.

Current caliber with highest accuracy. Time accuracy: annual rate within ±20 sec (equivalent to a monthly rate of ±3 sec) and rear power reserve (3 days) indicator.<ref name="gs9r"/>

* '''9RB2''' : 34 jewels, date.

==Notes and references==
{{reflist}}

{{Seiko}}

[[Category:Watches]]
[[Category:Epson]]
[[Category:Seiko]]
[[Category:Timekeeping components]]
[[Category:Japanese inventions]]

[[de:Seiko#Spring Drive]]

Spring Drive - Revision history

2A0B:5F04:5024:3700:4565:C377:7284:4352: /* Calibers */Added content (specified that the Calibre 9RB2's power reserve indicator is rear-facing, like Calibre 9RA2.