====== Spring Drive ======
**Spring Drive** is an electro-mechanical watch movement technology from [[Seiko]] noted for extreme accuracy and timing precision.

===== History =====
Seiko began working on hybrid electronic/mechanical watches in the 1960's. They produced a number of [[electric watch]]es which used a battery and motor for power and a conventional mechanical [[gear train]] and escapement for timing. They also produced the first successful mass-market [[quartz movement]]s, initiating the [[quartz crisis]] and nearly destroying the Swiss and American watch business. Quartz watches use a battery and motor for motive force and a quartz oscillator rather than [[escapement]] for timing, making them extremely accurate and reliable.

In [[1977]], engineers at [[Suwa Seikosha]] invented a method of timekeeping for a mechanical watch using a rotating disc between electro-magnets. This concept differed dramatically from all earlier watch technologies (mechanical, electric, and quartz) in that the gear train is continually in motion, with no stop/start impulses, as is the case for a mechanical escapement, or intermittent movement, as in quartz.

The key to Spring Drive technology is the "tri-synchro regulator", which manages the mechanical energy of the [[mainspring]], the electrical energy generated by the regulator, and the electromagnetic energy used to control the glide wheel. The speed of the glide wheel is measured 8 times per second and compared to a quartz timer, creating a feedback loop to brake the glide wheel or allow it to accelerate. The gear train is constantly in motion at very close to ideal speed, deviating by less than 1 second per day and allowing precise timing.

This concept was continually developed over the following two decades before being announced in [[1997]] and presented at the [[Basel Fair]] in [[1998]]. A Spring Drive [[Credor]] was presented in [[1999]]. The first Spring Drive movements were [[hand winding]], with an [[automatic]] movement arriving in [[2005]].

===== Applications =====
Spring Drive technology is reserved for Seiko's high-end lines [[Grand Seiko]], [[Credor]], [[Galante]], [[Izul]], [[Ananta]], and [[Prospex]]. The Grand Seiko Chronograph is considered one of the most advanced and accurate chronographs in the world, while the Spring Drive [[Credor Minute Repeater]] is a $400,000 [[grande complication]].

Seiko currently produces three Spring Drive movement families 

  * [[Seiko 5R]] - [[Seiko]]
  * [[Seiko 7R]] - [[Credor]]
  * [[Seiko 9R]] - [[Grand Seiko]] and [[chronograph]]

===== External Links =====
  * [[http://watchtime.at/archive/wt_2005_06/WT_2005_06_136.pdf|Seiko's Next Big Thing: Spring Drive]]


{{tag>Seiko Terms}}