Which Seiko automatic movement is the best? – Part II

The ‘best Seiko watch movement’ saga continues…

So far, we spoke about the 6R and 7S families of Seiko’s mainstream automatic watch movements and drew a bit of a comparison between the two. Their designs in their lineages stay pretty much the same; it’s their build and material quality that got enhanced over time.

Now we move onto other newer movements: The 4R35 family. We will skip their predecessor the 4R15/4R16 movements, for the 4R35 was introduced to bring improvements upon them in terms of manual hacking and winding options.

The 4R35 was introduced in 2010. It found way into a varied number of watches, irrespective of style. While on one hand you’ll find it nested within something as sophisticated as the Seiko Presage Automatic Zen Garden; on the other, you’ll find it among serious outdoor pieces (this Seiko Prospex Automatic Japan Made is a good example); some as extreme as the Seiko Prospex Turtle Save The Ocean Automatic.

Other closely related members of this family are the 4R36 (a Seiko-only version of the caliber NH36), 4R37, 4R38 and 4R39, all released in 2011. The entire 4r3x family operates at 21,600 vph, all featuring sweep hour, minute, and second hands. The Cal. 4R71 was introduced in 2018 and is similar to the 38 technically but was created for skeleton watches.

Points where they differ:

  • 4R37 and 4R39 get 24-hour sub-dials.
  • The 4R35 and 4R37 feature date windows as opposed to the 4R36 with both day and date within a single window.
  • The 4R35 (A) has 23 jewels. The 4R36, 4R37, 4R38 and 4R39 got 24. Later, it was revised and was given one extra jewel. This is Caliber 4R35B.
  • The 6R15 has a different mainspring, barrel and adjustment lever, which gives it a -15/+25 accuracy and a 55h power reserve. For the 4R series, -35/+45 seconds and a 38–42 h power reserve are averages. Both can be tuned to match COSC standards, but not for very long.

What about Spring Drive? Isn’t it mechanical, too?

Long answer: All Spring Drive movements are automatic and a small number of them are hand-wound spring drives. It is the only movement that expresses the natural and continuous flow of time.

Short answer: Almost completely mechanical; still, supremely accurate.

The Spring Drive is one of the most discussed and debated movements in the world today, for the mystery that resides in it. It is mostly associated with Grand Seiko, but is found in many other very high-end Seiko models apart from the Ananta and the Galante. The success and fame of the Spring Drive is radical, though surprisingly, only a handful among those who bought it actually understands how it works.

An oversimplified description of its working principles would say that Spring Drive combines the accuracy of quartz with mechanical beauty. Does that sound like Kinetic? Read on…

The Spring Drive movement is something altogether new in its concept; not just a rotating mass generating its running power mechanical automatics alike. It has no fundamental dissimilarity with mechanical movements save one tiny, critical point. The escapement has been replaced with a tri-synchro regulator, the thing that controls (the flow of the mechanical, electrical and electro-magnetic energies the mainspring generates. The regulator gets its name for the three diverse forms of energy it deals with.

The regulator’s one-way motion is inherently more stable and durable and thereby, highly precise (+1 second/day). Its seconds-hand runs perfectly smooth and it runs with an absolute silence, since there is no escapement. The circular, uni-direction rotation of the glide wheel imparts the hands their unique glide-motion.

Spring Drive has a l..o..n..g power reserve (72 hours) that delivers smoother than any; thanks to the new generation mainspring made from a special, in-house,high-elasticity alloy – the Spron 510. It is also highly resistant to heat and corrosion and winds faster, too! It’s the Magic Lever that boosts its efficiency for automatic winding. Compared to the Swiss-style winding-system, Magic Lever is minimalist; using fewer parts for the same task. It’s a 1959 Seiko invention that’s been reworked for the SPRING DRIVE; now, it’s fitted directly to the rotor’s shaft. Result? Greater efficiency, shorter winding period and a longer power reserve.

Want more info? Find it here.

Working of the Spring Drive

In simple words: The power from the mainspring is transmitted via a gear train to the Tri-synchro regulator, which controls the speed at which the glide wheel rotates, by electromagnetic braking. It also converts a small part of the transmitted energy into electricity. This powers the Spring Drive crystal by generating a magnetic force to regulate the speed of the glide wheel.

From here, ideally, we should go to the Spring Drive Chronograph movement. But it will take some time before we return with details about this perfect platform for luxury chronographs.

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