The ethereal revolutions of the spherical tourbillon within a swivelling case
La Cote des Montres - March 29th, 2008
Representing a splendid approach to the quest for absolute precision, the three-dimensional motion of the spherical tourbillon fascinates observers by the exceptional speed of rotation of its two carriages, with the inner one completing a full turn in 18.75 seconds, while the outer one performs a more conventional one-minute turn. Universally acclaimed at the time of its launch barely four years ago, this revolution in the tourbillon world now finds an entirely natural aesthetic expression in the Reverso, with its distinctive shape that further highlights the absolute beauty of this peerless technical accomplishment.
When the Manufacture Jaeger-LeCoultre first unveiled this avant-garde innovation in 2004, the Gyrotourbillon I took the watch industry by storm as the first-ever spherical tourbillon. Composed of two carriages mounted on axes set at a 90° angle, this horological microcosm is still the only mechanical device enabling a wristwatch to break completely free from the detrimental effects of gravity on its timekeeping precision.
A tribute to Fine Watchmaking, paid by an outstanding mechanical innovation
Embodying a mechanical marvel in its own right, the spherical tourbillon and the hundred or so parts composing it exercise an irresistible fascination by the complexity, speed and beauty of its three-dimensional motion. Eager to enliven still further the entrancing vision provided by this unparalleled watch mechanism, the designers of the Manufacture decided to enhance its already remarkable visual appeal by adding a touch of colour. To achieve this, they suggested that the technicians perform a daring thermal treatment on one of the most delicate parts of the mechanism, the now famous cylindrical balance-spring with end curves, in order to give it a bluish tint similar to that of the hour, minute and power-reserve hands. And since Jaeger-LeCoultre’s choices are always simultaneously dictated by both functional and aesthetic criteria, the arms of the balance were meticulously open-worked to create a slender elegance that also implies a considerable reduction in weight.
The barrel itself is fitted with a cover and a sapphire crystal so as to reduce friction on the mainspring. The energy it stores is thus entirely available for the movement in order to ensure a respectable 50-hour power reserve. Meanwhile, a subtle device placed on the barrel avoids any risks related to excess or insufficient tension. This means that when the watch is being wound, the system blocks the winding process before the spring becomes overly taut. Conversely, the movement stops before the progressive unwinding is liable to adversely affect the watch’s rating precision.
The extraordinary manually-decorated Jaeger-LeCoultre Calibre 174 is composed of 371 parts. Connoisseurs of fine watchmaking will appreciate the hand-raised and polished interior angles as well as the exquisite rounding off the intermediate carriage bridge. The German silver bridges and mainplate feature file-drawn edges, as well as hand-raised and polished angles. The surfaces are adorned with Clous de Paris, Côtes de Genève, circular graining or satin brushing, all serving to accentuate the graphic strength of this splendid rectangular movement. These ornamental touches create splendid contrasts with the steel mechanisms and the gear wheels coated in yellow gold. Finally, the plate features a screw of which the purpose is liable to remain a mystery for generations of watchmakers, since it will reveal the secret of its function only to micromechanical adventurers prepared to take the time required to grasp the enigma behind the running of this matchless mechanical calibre.
A key feature of the Gyrotourbilon 2
The cylindrical balance-spring with end curves
The second version of the Gyrotourbillon is distinguished by an essential organ: the presence of a cylinder-shaped balance-spring with end curves. This component was invented by English watchmaker John Arnold, who had it patented in 1782. Due to the complexity involved in its production and the difficulties implied by attempts to miniaturise it, this ingenious discovery which guarantees a regular and perfectly isochronous development of the balance-spring was reserved exclusively for marine chronometers and a few generously sized pocket-watches. It thus appeared doomed never to drive a wristworn mechanism. Innovative watchmakers chafed at this regrettable situation, since its rating characteristics are unanimously considered to be infinitely better than those of a flat balance-spring.
Nonetheless, all obstacles and pitfalls, however insurmountable they might appear, inevitably spur the engineers and watchmakers of the Manufacture to decisive action. The latter were able to grasp the opportunity represented by the spherical tourbillon and to present a cylindrical balance-spring nestling at the heart of a wristwatch. Combined with the specific advantages of the spherical tourbillon, this innovation represents a breakthrough in the field of accuracy and paves the way for a level of rating precision that is simply unprecedented on a timepiece designed to follow its wearer’s arm movements.
The extraordinary complexity of the spherical tourbillon
Embodying a major step forward in the history of mechanical horology, the spherical tourbillon offers wristwatches the same advantages that the classic Breguet tourbillon had brought to pocket-watches. Since the late 18th century, the tourbillon mechanism has freed watch movements from the influence of gravity on the regulating organ and its adverse effects on precision. This prodigiously designed mechanism serves its true purpose in a pocket-watch, which generally sits upright in a waistcoat pocket. However, the usefulness of a traditional tourbillon is far less obvious in a wristwatch, which is usually worn in a horizontal position. This particular situation requires the watchmaker to perform adjustments in several positions in order to determine a satisfactory average rate.
Through its conception and its construction built on two axes set at a 90° angle, the spherical tourbillon is the only device that compensates for the effects of gravity in all positions. Nonetheless, actually producing it called for the use of ultra-light high-tech materials in order to create a mechanism able to simultaneously drive the rotation of both carriages. Their speeds of rotation are so fast – one turn per minute for the outer carriage and one revolution in just 18.75 seconds for the inner carriage – that the balance maintains constant amplitude, whichever way it is oriented. For the first time in watchmaking history, the exactness of a watch is thus entirely independent of the position of the timepiece itself. Loyal to the uncompromising principles that govern each of its decisions, Jaeger-LeCoultre refused to take the easy path to achieving this result by reducing the size of the balance or the frequency of its oscillations. In order to guarantee infallible accuracy, the Reveros Gyrotourbillon 2 is equipped with a large gold balance that is fairly insensitive to vibrations or shocks, has an inertia of 12.5 mgxcm2 and imperturbably oscillates at a rate of 28,800 vibrations per hour. In an ultimate touch of luxury and in order to avoid any alteration in the rating in case of impacts, adjustments are made by means of gold inertia-blocks arranged around the rim of the balance.
An absolute Reverso
For a new dimension in time measurements
In terms of its horological functions, the Reverso Gyrotourbillon 2 displays the time by means of two flame-blued steel hands moving over an off-centred sapphire subdial. A fine engraving on the wheel to the left of the dial enables one to read off the time on a 24-hour scale. Meanwhile, the seconds are indicated by a blue index that is actually part of the outer tourbillon carriage.
On the back, a hand integrated within the movement indicates the power reserve on a sector-shaped bridge. Nonetheless, at the very moment when a Jaeger-LeCoultre watch appears to have revealed its essential characteristics, a new element consistently overturns the global view that an attentive observer is struggling to gain. For this particular model, in order to house the manually-wound Calibre 174, the engineers of the Manufacture had to design an entirely new swivel case that nonetheless complied with the inimitable DNA of the Reverso. By the very nature of its operating principle, the spherical tourbillon calls for a thicker type of envelope in order to operate in perfect freedom and security. After making countless prototypes based on highly complex crystals and spheres cut from sapphires, technicians and designers finally managed to accommodate the thickness of the tourbillon within an apparently classic case and sapphire crystal. Representing the height of refinement, this case is even equipped with a bolt inspired by the system used on the Reverso grande complication à triptyque, in order to prevent any inadvertent opening of the watch. The case is water-resistant to 30 metres and fitted with an integrated leather strap ensuring exceptional comfort on the wrist. As befits such a prestigious watch, the Reverso Gyrotourbillon 2 will be issued in a strictly limited platinum edition of 75.
Nonetheless, any watchmaking devotee will soon forget the subsidiary features of the Reverso Gyrotourbillon 2 and simply turn his gaze over and over to the extraordinary vision afforded by Jaeger-LeCoultre Calibre 174 and the captivating revolutions of the spherical tourbillon as it exercises its truly irresistible force of attraction. As the absolute Reverso, the Gyrotourbillon 2 embodies a unique accomplishment that could only emerge from a Manufacture that has allied traditional know-how with an indomitable spirit of innovation for the past 175 years. This timepiece, boasting a degree of precision on the wrist that breaks entirely free of the power of gravity, illustrates the creative strength that nurtures the countless transformations of the Reverso, the watchmaking icon appearing in consistently reinvented and perpetually fascinating new forms of expression.