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Blancpain - The L-evolution Tourbillon Grande Date

Blancpain The L-evolution Tourbillon Grande Date

Is the dial really the ideal place for all indications? Blancpain proposes a unique and better answer for the power reserve.


Lettres du Brassus  - No 10 Jeffrey S. Kingston  



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Tradition or logic? Over the nearly three centuries of fine watchmaking, certain design standards, or if you are a business consultant, business practices, have evolved and cemented themselves in place. None more than the placing of all watch indications on the top surface of the dial. Glance at the face and there they are, no matter how many hands or disks it takes to do the job of displaying all of the complications reposing beneath the surface. Traditional, yes. But is it always logical? Certainly for many indications not only is it logical to put the display on the face of the dial, but it would be nonsense to do otherwise. Do you seriously want to mount the case that hour and minute not be immediately readable on the face? 

In fact, as the exception that teaches the rule, one or two independent watchmakers have produced watches that actually hide the display of time forcing the owner to “do something” to extract hour and minute, or worse, have proposed timepieces that dispense altogether with any hour-minute indication. So consigning these horological aberrations to the trash bins where they deserve to reside, what tradition teaches about watch displays is almost always fully supported by logic.

But not 100% of the time.

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Take the power-reserve indication. Without question this is one of fine watchmaking's grand complications. The power-reserve complication shows the degree to which the watch is wound, or said more practically, the amount of wind left in the main spring barrel before the watch will be unwound and stop. Particularly for a timepiece which is not worn every day, it fulfills the vital purpose of informing the owner of the state of wind of the watch and whether there is imminent peril of the watch winding down. But once the watch is strapped onto the wrist, particularly an automatic watch, is there really any purpose of placing the display of the state of wind on the surface of the dial? Logically, all the owner or user requires is for the watch to show whether or not there is a need to take action to wind the watch before putting it on the wrist, at which point the automatic winding mechanism will take over. Similarly, when the watch is taken off the wrist, it is useful and logical to have information on the state of wind to know whether the watch will continue running until the next time when the owner plans to wear it.

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With this understanding of how owners will put a power-reserve indication to practical use, does it really make sense, or said another way, is it logical to place the display on the dial? The times when the indications are the most important are when the watch is placed on the wrist and when it is taken off. So while tradition teaches that power-reserve indications are to be placed on the dial, logic points to a different solution. The vital purpose of the complication can be completely fulfilled if the display is on the back of the watch, and if it is placed there then needless complication can be removed from the dial, increasing the readability of all of the other dialside indications.

This is precisely the thinking that led Blancpain to the design of the L-evolution Tourbillon Grande Date Réserve de Marche sur Masse Oscillante. But Blancpain's analysis did not stop there. As it reasoned that the power reserve should be placed on the back of the timepiece, the designers saw an opportunity to engineer a solution which had never before been achieved. Why not place the powerreserve indicator on a movement element intimately tied to this display, the winding rotor? Of course that is logical; the power reserve shows the state of wind and the winding rotor is the component that performs the winding function.

Much more is involved, however, than mere placement of power-reserve subdial on the winding rotor. Because the winding rotor most decidedly is not fixed in position, oscillating over 360 degrees of rotation, any display placed upon it would be both difficult and annoying to read if its subdial were mounted solidly on the rotor and thus remained in a fixed position relative to the rotor itself. How pleasurable would it be to try and extract the reserve information if the rotor were in an inverted position and carrying an inverted indication with it? Therefore, Blancpain decided early on that the power reserve subdial would itself have to rotate to keep its dial and hand in a constant vertical position so as to facilitate readability.

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What emerged from this world first placement of the power-reserve hand and dial on the winding rotor was a system far more complex than a traditional display. It is useful to think of Blancpain's innovative system as having four principal elements: i) a differential; ii) the drive gearing for the power reserve hand; iii) the drive gearing for the dial, and iv) a clutch which operates when the watch is fully wound.


THE DIFFERENTIAL

The winding barrel of a watch, which is typically composed of a drum, a mainspring coiled around a shaft (generally referred to as the “arbor”) and a cover, has two principal modes of action: the storing of energy from the winding of the watch and the release of energy to the running train of the watch. For winding, there is a ratchet wheel fixed to the barrel's shaft that is in turn connected to the crown for manual winding and, in the case of a self-winding watch, engaged with the automatic gear train.

For the delivery of energy to the running train of the watch, the barrel's drum via a wheel solidly fixed to it is engaged with the running train of the watch that, of course, passes through intermediate wheels to the balance/escapement. The power-reserve system has to be connected to both of these principal components of the barrel, that is the ratchet (for the winding of the barrel) and the barrel (for the running of watch). The reason is obvious: if the power-reserve hand is to display the state of wind of the barrel, it must take into account not only the unwinding of the barrel as it delivers energy to the running of the watch, but as well the winding of the barrel as either the winding rotor or crown rewinds it. If you are mechanically inclined, the description of a system which must combine two different inputs from two gear trains should suggest to you the use of a differential. That is exactly what Blancpain has done, utilize a differential to combine the inputs from the unwinding and winding sides of the mainspring barrel.

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DRIVE GEARING FOR THE POWER-RESERVE HAND

Attached to the axis of the differential is a pinion. This pinion, A, turns both clockwise and counterclockwise, as the barrel winds or unwinds. Basically, the drive train for the hand serves to transfer the rotation of this pinion A, which of course is the power-reserve indication, to a position on the winding rotor. This is done via a train of four gears. Diagram 1 shows this drive train. Pinion A is connected to wheel B whose large diameter serves to span across the winding bridge of the watch and to deliver the rotation to the center of the movement. Wheel B is connected to a double thick wheel C which is located at the center of rotation of the winding rotor. One more wheel is required to reverse the direction of rotation and that is pinion C2 which is engaged with the second half of the center wheel C. The pinion C2 is engaged with wheel D, upon whose axis the power-reserve hand is mounted.


DRIVE GEARING FOR THE POWER-RESERVE DIAL

The object of the dial drive train is to maintain the power-reserve dial in a constant position as the winding rotor which carries it rotates. This is accomplished via a gear train which starts with fi xed wheel E. As the winding rotor rotates, it carries around with it a pinion, F, which is engaged with the fixed wheel. That pinion, F, operates as a reverser gear and, in turn, engages wheel G, upon which is mounted the power-reserve dial. The result is that, as the winding rotor turns, the power-reserve dial turns in the opposite direction, at the same speed, so as to maintain a constant orientation. 

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There is one additional subtlety associated with the maintenance of a constant orientation of the power-reserve dial. As the winding rotor turns, it is also carrying around with it the wheel D, upon which is mounted the power-reserve hand. The rotation of the winding weight, therefore, would cause the hand itself to turn in an opposite direction as wheel D moves relative to wheel C, which does not turn with the winding weight. However, even though the power-reserve hand rotates opposite the direction of movement of the winding weight, as the power-reserve dial also rotates in the same direction as the hand, the indication of the hand on the dial will remain unchanged.

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THE CLUTCH

There is one additional complication which arises from the mounting of the power-reserve indication on the winding rotor. Blancpain's movement designers had to address the problem of a fully wound barrel for this system that rotates with the winding rotor even when the barrel is full. At full wind, the hand comes up against a stop, which is the rim of an applied marker, H, which is mounted on the dial. But as the hand is connected through its gear train to the differential and further as its gear train would continue to rotate with the winding rotor, Blancpain devised a clutch system, I, to disconnect the hand and its associated wheel, D, from its train when the watch is fully wound. This protects the movement from damage as the hand's gear train would otherwise continue to turn against a system which is fully wound. Not only does the rim of the applied marker, H, function as a stop for the hand at full wind, it serves to cover the mounting assembly for the winding rotor creating the illusion of a oscillating weight that is turning in space.

The L-evolution Tourbillon Grande Date Réserve de Marche sur Masse Oscillante is offered in both red-gold and white-gold versions.

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