The Girard-Perregaux Constant Escapement is now integrated into the movements that will animate the new models in the brand's Haute Horlogerie collection. Based on the prototypes presented in 2008, it has taken five years of development and refinement to realise this concept in a new movement. The name of Constant Girard, besides being one of the historical figures of the Maison, takes us back to a notion of mechanical watchmaking that has subjugated creators since the dawn of time: constant force. The brand's aim was to achieve this through an entirely innovative approach. To assess the problem and truly understand the scope of the innovation, it is necessary to remember a few basic concepts. At the heart of a mechanical watch is the regulating organ, which regulates the flow of energy received by the barrel to animate the gear train and the rotational speed of the hands. The classic image is that of a tap controlling the flow of water. The main factor is not so much the speed of the beats of this heart, the frequency selected, but their regularity. The waltz can be three-stroke, four-stroke, even a thousand-stroke, but the essential thing is that it maintains the beat throughout the duration and to the end. Various systems were invented before the famous Swiss anchor escapement became established in wristwatches. However, it suffers from one defect: it can only return the energy it receives from the barrel, which diminishes with the passage of time. This energy, which defines chronometric precision, is too strong at the beginning and insufficient at the end, like a machine running out of steam. A curve, which both tickles and annoys watchmakers, illustrates the phenomenon: the amplitude of both the angle of rotation of a balance wheel and a pendulum, which diminish their movement at the end of the stroke. The principle of a constant-force escapement is that the energy of the barrel is returned from the escapement to the regulator (balance) in a constant manner. To achieve this, the idea was to integrate an intermediate device into the escapement, consisting of an extremely thin ribbon that constantly accumulates energy up to the threshold of instability and then transmits it fully and instantaneously before restarting the cycle. The phenomenon is known as buckling, which is the transition from the state of compression to the state of bending. Energy specialists speak of inflamed ribbons. Here, the ribbon, which is made of silicon, is the thickness of a sixth of a hair. It plays the role of a micro-energy accumulator. With this ribbon at the point closest to its state of instability, an infinitesimal amount of energy - a micro-pulse given by the balance (less disruptive than in the anchor escapement) - is sufficient for it to move from one stage to the next, using this movement to revive the balance and compensate for the variable energy of the barrel, releasing the same amount of energy each time. Unlike other systems that propose a constant force provided by an average, this is a true constant-force escapement because the force is instantaneous and continuous. It is, in fact, perfectly measurable by laboratory analysis methods. The designers chose a double, symmetrical construction. This is not for aesthetic reasons, but as a matter of balancing the forces at the centre of the balance, avoiding a concentration of constraints at this point, thus ensuring a completely free point of rotation. The one-piece band is fixed at both ends and plays a decisive role in closing the contact point where the micro-impulsion is exerted that will trigger it instantaneously. Behind a relatively simple principle lies the need for absolute precision in manufacture, which would have been impossible before the use of silicon and the advent of new component production techniques such as deep engraving (DRIE). The partnership with the CSEM (Swiss Centre for Electronics and Microtechnology) in Neuchâtel was decisive. Experienced watchmakers and physicists performed complex calculations to determine the characteristics of the band and other factors influencing the yield point. In the end, the structure of the device comprising the ribbon is monolithic. The latter is as if in virtual levitation and suffers no friction except for the moment of the impulse and the bending of the belt. The belt's energy is transmitted directly to the balance. Since the ribbon is the key element of the Constant Escapement, its natural vibration was favoured when choosing the frequency: 3 Hz (21,600 vibrations per hour) for the magic to work. But the future remains open and some tests have already been carried out at other frequencies. However, the challenge is not the high frequency. To accommodate this exceptional movement, with its original and innovative escapement, the case had to live up to the engineering masterpiece by enhancing it, without hiding it. With the Haute Horlogerie Constant-Force Escapement collection, the first model of the Constant-Force Escapement is distinguished by its resolutely technical and contemporary design while respecting the brand's codes and its creative tradition. The movement is housed in a comfortable 48 mm round white gold case with a rounded caseband. To offer maximum visibility to the escapement, its butterfly wings and its vibrating ribbon in its median axis, the hours and minutes are positioned in an off-centre dial at 12 o'clock. The latter is enclosed between two power reserves that make up the double barrels. The linear power reserve appears at 9 o'clock. The entire lower part of the watch is reserved for the Constant Escapement, towards which all eyes converge and which brilliantly occupies the main stage, beating at a frequency of 3 Hz, 21,600 vibrations per hour. Visible beneath the anti-reflective sapphire crystal are the three bridges, the brand's emblem, which play their structural role in an unprecedented arrangement. This hand-wound calibre is no more than 8 mm thick, while the case housing it is 14.63 mm. The movement is visible through the sapphire glass back with 6 safety screws, through which one can admire the remarkable three-dimensional construction of an exceptional movement from a different angle. Equipped with a hand-sewn alligator strap with a folding clasp, the model is offered in a non-limited edition as it will become part of the Girard-Perregaux Haute Horlogerie collection.
Girard-Perregaux Constant Escapement L.M. (Luigi Macaluso)
Technical specifications
White gold case
Diameter: 48.00 mm
Bezel: circular satin-brushed interior
Glass: domed anti-reflective sapphire
Crown: white gold with engraved GP logo
Dial: silvered grené with rhodium-plated applications
Hands: dolphin
Back: sapphire glass, closed with 6 screws, hand-engraved inscriptions
Water resistance: 30 metres
Girard-Perregaux movement MVT-009100-0007
Mechanical hand-wound
Calibre: 17½ ''
Frequency: 21,600 alt/hour - (3 Hz)
Power reserve: approx. one week
Rubies: 28
Number of components: 271
Functions: hours, minutes, central seconds, linear power reserve
Black alligator strap
Folding buckle
Reference : 93500-53-131-BA6C
