skyeriding
900
My theory based from my observation. Interestingly, there is another brand which does something similar. And, another brand that missed that opportunity.
May 13, 2017,15:34 PM
But before we get into that, lets simplify with a different example, to make it easier to understand.
You can skip this whole section if you want to get straight to the point:
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Imagine a normal chronograph with a balance wheel at 2.5Hz, or 5 beats per second. This means that the chronograph has a precision of 0.2 seconds as the smallest timescale it can measure. A normal chronograph is "stopped" when the clutch (either horizontal or vertical) disengages, so the main geartrain stops powering the chronograph seconds hand at that instantaneous moment.
So in theory, why can't I simply take that basic 2.5Hz movement, gear it up many times to get a higher "precision" when the clutch releases? A normal chronograph seconds hand takes 60 seconds (naturally) to revolve once around the dial. What if I gear it up say, 60 times, so it flys around super fast, once a second?
The immediate answer is that the ticking of a watch isn't "smooth", because of the escapement. If you attach this gearing system to the seconds hand, you get something similar to a "foudroyante" hand. A foudroyante is a feature/complication on some watches where the seconds hand completes one revolution on a dial/subdial per second. A good example is the JLC Duometre. If you notice, the seconds hand moves in quick, segmented "steps" , matching the beatrate of the balance wheel of course. This is an "impulse" step as the escapement releases by the pallet fork - it is not a linear smooth rotation of the balance wheel.
Now, there is one brand however that did it. You guessed it - FP Journe. Namely, the Centigraphe.
The Centigraphe works by having a foudroyante chronograph seconds subdial - by having a "clutch" connected and geared to the escapement wheel of the watch. It is a 3Hz watch, but it has a foudroyante chronograph seconds subdial and is advertised to measure 1/100 of a second. It times this higher precision by having a vertical clutch of sorts disenganging this foudroyante even whene its halfway through the "impulse" of the ticking, which gives readings in between the 3Hz. Technically speaking, this is not 100% accurate as the foudroyante still "stutters" around, not a smooth continuous sweeping motion to match the linear scale of the 1/100 markings on the dial. This kind of mechanism is only technically 100% accurate if you have a perfectly smooth sweeping seconds hand.
Hence in theory, there is one brand that has missed on that opportunity. Who?
Seiko.
Grand Seiko makes spring-drive chronographs. As a quick recap, you will know that spring-drive works by having a "glide-wheel" which is essentially a flywheel that is regulated by electromagnetic braking. Therefore, this is the closest you can get to a purely "analog", smooth continuous sweep of seconds hand without any impulse or steps. Furthermore, they make a chronograph. In theory, if you gear up this chronograph seconds hand, you can get near unlimited precision - only dictated by how fine the markings you have on the dial!
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Back to the Montblanc. The Montblanc works in the same principle as the FPJ Centigraphe, but in a slightly different manner. At least, this is how I think it works!
Pay attention to this snapshot below:
What you see is that this is a 10-toothed gear. This is likely a foudroyante of sorts - it spins at a really high speed, "geared up" 10x of the chronograph seconds hand running at 1/100 of a second. Therefore, we obtain 1/1000th of a second.
When the chronograph is stopped, the column wheel rotates from the actuation of the stop pusher. This causes the "jaws" surrounding the 10-toothed gear to fall inwards, thus stopping this 10-toothed gear. Under this gear, is quite likely a retrograde cam of sorts. At the same time, the column wheel also coordinates another lever that forces the 1/1000s hand to mash against this retrograde hand, thus only giving the actual 1/1000s time reading when the chrono is stopped.
It is also quite likely somewhere within the geartrain, the gears are allowed to "slip", such that the sudden jolt of the jaws braking the 10-toothed gear will not cause any significant backlash/jamming of the rest of the mechanism.
Again, in theory it is not 100% perfect due to the tiny, miniscule "impulses" of the 1/100s escapement. However, for all practical purpose the 1/1000s is near-impossible for us to verify due to human limits. Thus its somewhat like a game of roulette - just depends on where the jaws land between those 10 teeth!
As an aside, I find it interesting this movement came out years ago - in the form of the TimeWriter II Chronographe Bi-Fréquence 1,000. But perhaps its a little obscure... At the same time, brands like Tag Heuer also does these high-frequency, 1/100s chronographs. I wonder who did them first, Richemont or LVMH? Or is it a collab?
Regards,
skyeriding