The Reason
Influenced by the original design of the Tourbillon with Three Gold Bridges pocket watch, this timepiece represents one of the stages in the evolution of the most important model in Girard-Perregaux’s history.
Its DNA has been directly inherited from the original pocket watch but with the addition of multiple technological advancements. The miniaturisation is the first element to be considered given the original large size of the pocket watch it’s based on.
Functions
An automatic winding, minute Tourbillon calibre with central minutes and hours indication.
A subtle and almost hidden element that differentiates this calibre from the original is the automatic mechanism driven by a rotor weight running concentrically with the barrel. The automatic train set between the rotor and then back to the ratchet wheel, winding the mainspring in the barrel can be seen on the back of the movement.
The design of the bridges remains faithful to the original pocket watch, with the arrow-headed bridges, and the three dimensionalities of the overall construction.
Technical Specifications
Case material 18ct white gold. Case diameter 44 mm with sapphire glasses. Water-resistance 3 atm. Calibre diameter 36.60 mm, height 8.40 mm. Frequency 21,600 Vph – (3 Hz). Number of components 310, Jewels 31, Oscillating weight platinum micro-rotor. Power reserve minimum 60h.
Today, the relevance of reducing the physical size of complications compared to their pocketwatch origins is overlooked, due to their frequent presence in the market place. It is made possible due to the technological advances in machining surrounding us, but this has also pushed watchmakers to work on another level of scale complexity.
A variation between the wristwatch and the pocket watch is the escapement. The original housed a pivoted detent escapement, which is not suitable in a wristwatch, it is not self-starting and risks stopping when the watch receives impacts during wear. The Swiss anchor/lever escapement replaces this.
The case back is fixed to the centre by 6 white gold screws. A silicon seal is sandwiched on the inner surface of the case back, pushing against the case centre to assure the case back remains water-resistant.
Full view of the movement still in the case. The movement is fixed into the case by two casing clamps.
To the right of the image is the automatic train and steel ratchet wheel fixed to the barrel arbor. To the left is the going train driving the watch.
The movement removed from the case (the crown and stem returned to their normal position in the movement).
No dial is present in order to emphasize the design and value of the movement whilst the watch is being worn.
The gold bridges are emphasized in this execution by the simple matt finished rhodium plated main-plate. On the original pocket watch the movement was in effect hidden behind the case back and only viewed when the two case backs were opened.
To view the movement from the dial side the hands were inverted in position to the original watch, traversing the movement and showing the hands on top of the bridges. This required designing the motion work, the wheels that drive the hour and minute hands, and locating them on the back of the watch.
The hands removed from the movement.
Removing hands from any watch is a delicate operation regardless of the dial. Here the process is more fragile, removing highly finished gold Dauphin hands without deforming them or scratching the mirror finish on the gold bridges.
The mirror finished, faceted Dauphin hands removed from the watch.
The Tourbillon bridge removed, revealing the cage.
The gold bridges are held in position by 4 steady pins and 2 large screws. The additional 4 small screws hold the top part of the bridge onto their pillars of the same shape as the ends of the arrow shaped bridges.
The cage removed from the movement revealing the gold coloured ‘fixed’ wheel screwed onto the main-plate that drives the escape-wheel pinion as the cage turns.
The Tourbillon cage removed. The blued steel index acts as a seconds hand. Although there is no dial, the time can be manually checked as the index points vertically every minute.
The centre bridge removed.
The skeletonised upper wheel acts as the barrel wheel driving the centre wheel pinion, even though the actual barrel with mainspring is hidden in its centre. The platinum micro-rotor can be seen through the skeletonised sections of the wheel.
The Girard-Perregaux name and ‘Automatic’ are both hand engraved.
The barrel bridge removed.
Close-up, lateral view of the barrel wheel driving the centre wheel pinion.
Lateral view showing the barrel under the top wheel, that in-turn sits in the centre of the rotor.
The barrel removed from the movement.
To the right, the ratchet wheel that is fixed to the barrel arbor underneath the movement.
The small rose coloured wheel partially hidden under the banana shaped bridge meshes with the steel pinion fixed to the rotor weight, driving the automatic mechanism.
The ball race for the rotor weight has ceramic instead of steel balls, not requiring lubrication, running quieter and producing less friction than the steel counterpart.
The barrel and rotor assembly removed showing their integration together.
An elegant solution resulting in an integrated micro-rotor that does not disrupt the overall aesthetics of the watch and retains a movement with conventional proportions but emphasizing the large three gold bridges.
The three bridges removed. The top one for the Tourbillon cage, centre bridge for the centre wheel and the lower bridge covers the barrel assembly.
The softer the material the more difficult it is to achieve a flat mirror polish. Hardened steel by comparison, is much easier to polish to the same result achieved here.
Close up of the gears under the main bridge on the back of the movement.
The setting mechanism to the left of the image, to the right the pinions that manually wind the barrel mainspring.
The rear bridge also acts as the cover plate for the motion work, the pink jewel in the centre limits the movement of the minute wheels vertically.
The large wheel drives the Tourbillon cage pinion driving the cage.
The rear bridge removed showing two trains of wheels.
Top right- automatic train leading to the barrel, the jewel set lever acts a click for the train preventing the train unwinding.
The automatic ratchet wheel and its jewelled click.
Recto-verso of the rear bridge.
The pinion at the bottom of the image is fixed to the Tourbillon cage.
The majority of the rear mechanism removed (but, in this image the going train is still in place).
A selection of wheels from the two trains.
Summary
The model shown here is a stepping stone in the evolution of this series. The changes made in this watch vary from technological, to design. The integration of the rotor into the same space as the barrel, the execution of the automatic train almost hidden on the back plate once assembled. The overall simplicity emphasising the Three Gold Bridges is cleanly and strongly executed but hold close to elements that make it clearly recognisable as Girard-Perregaux.
GALLERY
In the grid below are both images used in the description of this page plus more. Please click on the image to enlarge and see in full.
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