Grand Seiko Constant Force Tourbillon. Yay?


Grand Seiko Constant Force Tourbillon

Grand Seiko makes as good or better a watch as any mainstream Swiss watchmaker (cough Rolex cough). Grand Seiko makes timepieces that put some high horologists to shame (who shouldn’t be smoking weed in the first place). The Japanese watchmaker’s oeuvre now includes the Grand Seiko Constant Force Tourbillon, the world’s first constant force tourbillon. How great is that? . . .

Well, the T0 (that’s a zero not an “o”) is Grand Seiko’s first tourbillon, their first constant force mechanism and their first constant force tourbillon. Given the ticking sound the movement makes (via a ceramic stop wheel), it’s also their first hip-hop beat track.

Seiko spent seven years developing the T0. The resulting technical accolades are completely lost on John Q Public. Well, not completely. Simply put, the Grand Seiko Constant Force Tourbillon is the world’s most accurate mechanical watch.

Hang on. Make that the world’s most accurate disembodied mechanical watch movement. Also note: the T0’s tourbillon is not the key to this accomplishment.

Grand Seiko Constant Force Tourbillon front

If you leave a disembodied watch movement on a shelf with the dial vertical, gravity exerts a measurable effect on the escapement and balance wheel.  Mounting those bits in a rotating cage cancels out gravity’s influence and improves accuracy. Not by much, but some.

What blessing does a tourbillon bestow upon a wristwatch, aside from bragging rights, a huge price tag and the horological equivalent of a circus side show ? Nothing much, accuracy-wise, veering dangerously close to “none.”

The attitude of a wristwatch changes frequently from vertical to horizontal depending on the wearer’s hand movement. The effect of a tourbillon is small compared to the change in rate resulting from changes from vertical to horizontal, and vice versa.

Not to put too fine a point on it, the Grand Seiko Constant Force Tourbillon’s world-beating accuracy is down to other stuff.

As an English major from a minor university, I’m not qualified to provide a technical analysis of the T0’s innovations. Click here to read The Robb Report’s not entirely boring explanation, or here to read Grand Seiko’s longer, less jargon-filled story of the T0’s genesis.

Grand Seiko Constant Force Tourbillon top view

Bottom line: Grand Seiko claims the T0 is accurate to less than half a second a day.

That’s 1.5 seconds more accurate that the 3230 movement found in Rolex’s recently released Superlative Chronometer-rated Submariner – which has the disadvantage of being an actual watch, rather than a disembodied movement.

Grand Seiko 9R Spring Drive movement

The Grand Seiko Constant Force Tourbillon is significantly less accurate than Grand Seikos’ own 9R Spring Drive movement, accurate to one second per month.

And considerably less accurate than the Longines Conquest V.H.P.  and Grand Seiko’s own 60th Anniversary Quartz. Both [actual] watches are accurate to five seconds a year.

That’s not to take away the enormity of GS’s latest accomplishment. The Grand Seiko Constant Force Tourbillon is a technological tour de force. But to what end? Here’s their take on the movement’s raison d’être.

Seiko Observatory Competitions movement

The T0 is just a concept creation, but it is far more than that. As the Observatory Competitions significantly developed the performance of Grand Seiko, the pursuit for higher accuracy and the watchmaking technologies including movement finishing of T0 contributed to refining the revolutionary mechanical caliber, 9SA5. T0 shows a brilliant future for Grand Seiko rather than simply showcasing its exceptional technological expertise.

Got it! Lessons learned from this project inform Grand Seiko’s other products.

Meanwhile, the short-sighted horological press and single-minded collectors keep asking the crass if entirely obvious question: when will the  GS stuff the T0 into a watch? Will there be a Godzilla edition?

T0 bits and pieces

OK, that last one is me.

Anyway, I’m kinda bummed by the Grand Seiko Constant Force Tourbillon. I thought GS was above messing around with antiquated time-telling technology, of which the tourbillon is the poster child.

Takuma Kawauchiya, Product Development Dept. of Seiko Watch Corp.

Then again, I’d sell a kidney for a Grand Seiko pocket watch – a timepiece that would make good use of the T0’s update on Breguet’s spinny thing and provide a larger canvas for GS’s insane level of craftsmanship.

In any case – and I bet Grand Seiko eventually puts the T0 into an awesome case – hats off to Takuma Kawauchiya. For whatever reason, the Japanese horologist moved the backwards-looking ball forwards. And that’s saying something. What, I’m still not entirely sure. But something.


  1. I think it’s difficult to get a quartz timer at better than +/-15 sec per month without some sort of temperature management solution. Nice to see a mechanical watch movement approach that level of precision!

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