The Reverso grande complication à triptyque
Three faces for three dimensions of time
The Watch Quote™ - April 11th, 2006
Jaeger-LeCoultre Reverso grande complication à triptyque
75 years of eternal youth
The history of the mechanical measurement of time stretches across more than 700 years. No wonder, then, that it is full of tales which, in equal parts, give pride of place to particular inventions or people or – naturally enough – to the real heroes of this epic: the timepieces themselves. Some of these stories sound so fanciful as to be the stuff of myth but are nonetheless entirely true. One such concerns a wristwatch which is celebrating its 75th birthday in 2006 but which remains as youthful today as it was on its very first day. Better still, having reached an age by which most wristwatches have long since been consigned to history, the Reverso – the watch in question here – is positively blooming. But we’ll come to that later presently. First, a little introduction. The story of the legendary reversible watch begins long ago in British India, where colonial officers dedicated a large proportion of their spare time to playing the oldest team sport in the world. Polo first appeared more than two thousand years ago in the steppes of Asia before then moving on to seduce the Arab ruling class in Tibet. However, when an English lieutenant rediscovered the sport in India in 1859, polo suddenly became a very British sort of pastime, achieving astonishingly popular in a very short space of time. By the end of the nineteenth century there were already 175 or so polo clubs in the Indian subcontinent.
In some of these, the proud officers exposed not only their best ponies to the rough-and-tumble of matches, but also their watches. Now, at that period an ideological conflict was raging in the horological universe, where the new type of ’wristwatch’ had begun to challenge the traditional primacy of timepieces kept in breast pockets and attached to the body by means of a chain. Sports players in particular seized on the advantage of being able to glance quickly at their wrists in the heat of action, rather than having to reach awkwardly into their jacket pockets to find out the time.
It’s true, however, that these new wristwatches were neither without faults nor drawbacks of their own. Their Achilles heel, so to speak, was their use of crystal glass. Comparatively light impacts and shocks were enough to smash the watch glass, with predictably disastrous consequences for the dial and hands beneath. In hotly contested polo matches, the risks were particularly great. This sad state of affairs came to the attention of César de Trey, a Swiss businessman and distributor of Jaeger and LeCoultre watches who had gone to India in search of new markets. He had just watched a polo match at a club where he had met up with some old friends, when an English officer pushed the wreck of a valuable wristwatch under his nose. Hearing that César de Trey sold high-quality wristwatches, the officer challenged him to find a solution to this recurrent problem. The Swiss businessman listened to his grievances and promised to look into the question. On his return to Europe, he immediately relayed it to the only one of his commercial watchmaking partners he considered equal to the challenge, Jacques-David LeCoultre. The Manufacture in Le Sentier began to develop the first movements destined for use in the Reverso, while the two men contacted a Parisian engineer by the name of René-Alfred Chauvot, who applied himself to the problem with his usual creativity. One possible solution – protective bars across the glass, long known but lacking in elegance and by no means entirely effective – was jettisoned immediately. Only a completely new design could combine the necessary anti-shock function with the elegance demanded by a sophisticated clientele. It was in this context that Chauvot came up with his bold idea, described in the patent application dated 4 March 1931: "a watch capable of gliding in its carriage and turning over on itself completely."
Thus, depending on the activity in which he was engaged at the time, the watch’s owner could choose either to wear it front face up or – during polo matches, for example – to hide the fragile watch glass and instead expose its much tougher steel back. As such the watch’s pivoting case made it possible for it to turn its back on impacts and protect its dial.
Jacques-David LeCoultre and César de Trey were delighted with Chauvot’s idea. The Genevan casemaker Wenger, to whom they showed it, was immediately won over too. The watch with a pivoting case quickly went into production. To distribute the Reverso, Jacques-David LeCoultre and César de Trey founded Spécialités Horlogères, which bought back the patent and was quickly rebaptised Jaeger-LeCoultre.
Much more than a sports watch, the Reverso quickly became a cult object, appearing in its classic rectangular Art Deco version, which was perfectly in tune with the stylistic tendencies of the 1930s. If he chose, the owner could personalise the metallic second side with an engraving or an enamel design. And that’s how it all began for the Reverso, whose story of unprecedented successes reaches new heights in 2006 with the appearance of an entirely unique new model: the Reverso grande complication à triptyque.
The first watch to have three faces
Conventional wristwatches sometimes have two faces. However, moving between them is awkward and involves taking the watch from your wrist. That isn’t the case, of course, with the Reverso: a simple pivoting gesture is all it takes to pass from front face to back. And vice versa. In 1994, the Reverso Duo opened itself up to the wide world. Its first face displayed the traveller’s local time while the second remained anchored to his reference time. With a simple turn of the case, its cosmopolitan owner could obtain all the information he might need in the midst of his travels. The 1996 Chronographe Rétrograde explored other possibilities, diversifying its talents. Its front face indicated the time while its back face was dedicated to a chronograph function with a 30-minute retrograde counter.
Now, the Reverso grande complication à triptyque has arrived to overturn all conventions once more. Only the legendary reversible watch the Reverso could dream of combining three dials on a single wristwatch. And such a dream could only have been made reality, after more than three years of research and development, in a workshop whose extraordinary skills with horological complications are the fruit of long decades of patient application.
The precise division of time
Time is always with us. Our lives ineluctably have to sumbit to it – which explains mankind’s attempts through the ages to master it and measure it in as precise a manner as possible. Indeed, there is evidence that even the very earliest human civilisations attempted to seize time, this most precious of all commodities which runs its course steadily and evenly, without emitting even the smallest sound. The recurrent phenomena caused by the transit of the Sun and Moon across the celestial vault have always provided us with certain natural and readily observable units of time: the year, the lunar month and the day. But in order to adapt time to the exigencies of civil life, more frequent divisions are required: hence the addition of other units such as hours, minutes and seconds. These are all artificial, of course, and, considered in the context of mankind’s history on Earth, extremely recent. It was only in the middle of the fourteenth century, for instance, that the first mechanical clocks, the oldest and surely the most important invention of our epoch, started to divide the day into 24 hours of equal length.
The first clocks to carry minutes probably only appeared at the end of the fifteenth century. Seconds, the secunda diminutiva pars of the hour, followed at the end of the sixteenth century. The appearance of the second hand marked the onset of a ruthless struggle to make mechanical timepieces as precise as possible.
It was on the high seas that precision clockmaking had its baptism of fire at the end of the Middle Ages, when the discovery and conquest of the planet was a top priority for men of power and ambition. The success of ocean crossings depended in large part on sailors being able to determine their exact position at sea. In this, knowledge of the exact time played an important role, and was every bit as important as having enough water under the ship’s keel. Determination of the geographical latitude by the position of the stars posed no great difficulties. Calculating the longitude, on the other hand, was a much trickier business, and required, as soon became clear, clocks that could continue to run, in as precise a manner as possible, on the local time in the last port of known meridian throughout the voyage. Since the Earth takes exactly one day to make a complete revolution about its axis, time can be used to calculate geographical longitude, with precise measures of time corresponding to the distance between longitudes.
The first precision instrument created to fulfil this function was made in 1759 by an English carpenter named John Harrison. Between November 1761 and January 1762, the H4 chronometer made an 81 day passage aboard ship. At the end of the voyage, it showed an error of barely 5 seconds – and Harrison pocketed the prize offered by the British Parliament.
The feat was much discussed and – naturally enough – inspired emulators. Skilled clockmakers began to design instruments of great precision for use by sailors, the famous marine chronometers. The division of time into predefined and universally adopted units was carried out by means of a mechanism essentially consisting of a balance, a balance-spring and an escapement. The latter element is responsible for carrying out two quite different and delicate tasks: in the first place, it maintains the constancy of the vibrations of the balance and balance-spring by finely dosing the transmission of energy from the barrel; in the second, the escapement stops the uncontrolled action of the geartrain. It therefore carries out at one and the same time jobs requiring both precision and force.
It’s not surprising, then, that the makers of marine chronometers paid particularly close attention to this part of their mechanisms. The detached escapement, developed from the idea that the balance should be allowed to vibrate with the greatest freedom possible, was found to be best-suited to carrying out this complex combination of operations. Unlike the well-known anchor escapement, which intervenes at each vibration, the energy-dispensing impulse acts only once per complete vibration and in the briefest manner possible. The lever escapement can be considered a particularly successful variation on the detached escapement and as such is found in numerous Swiss-made marine and pocket chronometers.
Until now, however, wristwatches have had no choice but to do without the benefits of detached escapements. Because of the way they are constructed, impacts on the mechanism cause a perceptible ‘gallop’ in classical detached escapements which translates itself into a forward acceleration of the second hand and – obviously – runs counter to the exigencies of optimal timekeeping.
On the front, civil time, regular and ultra-precise
Jaeger-LeCoultre’s master watchmakers have just removed this anomaly. After carrying out extensive research into materials and the geometry of chronometers, they have created a new detached escapement which is perfectly adapted for use in wristwatches. The ellipse isometer escapement is based on well-established principles of construction, but manages to eradicate the disadvantages usually associated with them.
A careful look reveals that this new ensemble consists of four elements: the escape wheel, the roller, the blocking-lever arm and the blocking-lever. How the unit functions is comparatively easy to understand: the long blocking-lever arm along with a short but wide balance weight is fixed in the usual way by two pins. A spiral-spring ensures that its tip rests with a light but effective pressure on the flat surface of the ellipse and thus stabilises the blocking-lever arm. The ellipse blocks the movement of the escape wheel called for by the barrel. If the balance turns in the opposite direction to the hands, the roller’s impulse face misses the escape wheel by an infinitesimal distance of around two hundredths of a millimetre. Of course, the unlocking-pin, fixed upright on the roller, imparts a motion to the pallet of the blocking-lever, but it slides on the sloped surface without provoking any specific action. As such, the balance can move freely oscillate to the farthest point of its course. It then turns in the horary direction. At a certain moment, the unlocking-pin meets the flat surface of the pallet, which provokes a slight lateral displacement of the blocking-lever. Hence, the escape wheel benefits from a moment of liberty and begins to turn. One of its 15 teeth then immediately enters into contact with the vertical back part of the impulsion jewel and transmits to the balance the impulsion to keep it in motion. In the meantime the blocking-lever has repositioned itself and the next tooth of the escape wheel comes up against it.
Because of a high operating frequency of 21,600 vibrations per hour, the process finds itself back at its starting point every third of a second. The glucydur balance, which has an increased moment of inertia of 11.5 mg x cm2, has ten fixed gold screws and four adjustable ones to regulate the oscillation length. The variable-inertia balance wheel allows the balance-spring to beat freely without hindrance from index pins, which are superfluous in this configuration.
Jaeger-LeCoultre would never have been able to realise this masterpiece using only conventional materials. So that the ellipse isometer escapement can function perfectly in all positions and withstand impacts, the blocking-lever arm and the escape wheel are made of monocrystalline silicon. Years of research have gone into its application. It is extremely light, very hard, anti-magnetic and corrosion- resistant. The blocking-lever arm weighs scarcely 1.7 thousandths of a gram. Apart from its geometric characteristics, this new escapement has the further advantage of requiring no lubrication.
Still on the front, a titanium minute tourbillon
On traditional marine chronometers clockmakers used cardan suspensions to ensure that the balance and balance-spring always oscillated horizontally, thereby eliminating the negative influences of terrestrial attraction. Pocket- and wristwatches are different, however. This is where the tourbillon mechanism, invented in 1801, comes in: it imparts a regular rotary motion to the balance, balance-spring and escapement. As a result, the imprecisions caused by gravity cancel one another out in the course of each complete rotation of the cage. Tourbillons are most effective when used in conjunction with a detached escapement. Until now, this exceptional combination remained the privilege of clocks that were so rare they could hardly be afforded. Where wristwatches were concerned, the combination of tourbillon and detached escapement remained a utopian dream. But now, with the arrival of the Reverso grande complication à triptyque, a revolution is under way. Its manually wound movement, the Calibre Jaeger-LeCoultre 175, includes a minute tourbillon of an ethereal lightness, whose titanium filigree cage weighs just 0.08 grams. Counting its balance and ellipse isometer escapement as well, the weight of this world first still only comes to 0.29 grams. The cage, which also drives a fine second hand, turns on itself in a round aperture on the hour dial. This is where the hour and minute hands and the day/night indicator also appear. Its creators deliberately chose an eccentric location for the balance with screws so as to make it possible for the wearer to view the functioning of the ellipse isometer escapement. Each day, it delivers its impulse force with absolute precision 259,200 times. That’s 94 million impulses per year. Any further commentary would be superfluous.
On the back, sidereal time
So much for the face of the watch concerned with recording the exact time of day. The second face of this mechanical wonder is dedicated to astronomical observation. The fascinating starry sky unquestionably plays its part in timekeeping – when it isn’t covered with clouds. On the Reverso grande complication à triptyque, of course, no such veil exists. This is one sparkling spectacle that is always visible, no matter what time it is or what the meteorological conditions are like outside. A disc in an oval aperture in the dial, adjusted for the northern or southern hemisphere depending on where the watch’s owner lives, represents the angular displacement of the distant celestial bodies and the constellations.
This is no easy task, since sidereal time has its own particularities. The sidereal day is the time that elapses between two successive transits from the vernal equinox point to the meridian from the place of observation. The vernal equinox point is in fact an imaginary point which cannot be observed directly and which corresponds to the beginning of spring.
Expressed another way, the sidereal day is almost equal to the time necessary for the Earth to make a complete revolution about its axis. To be precise, the sidereal day is 3 minutes 56 seconds shorter than the mean solar day. All the same, it is also divided into 24 (sidereal) hours. Expressed mathematically, that means that a sidereal second lasts exactly 0.99726957 of a solar second. These are details that Jaeger-LeCoultre’s watchmakers could hardly ignore. And that’s why the Reverso grande complication à triptyque contains a mechanism designed to transpose the mean solar time into sidereal time. The disc of the celestial bodies and constellations therefore completes a turn every 23 hours, 56 minutes and 4 seconds.
Still on the back, a totally new zodiacal calender
Also represented on the second dial are the twelve signs of the zodiac. To explain the disc’s function we first need to consider briefly the most important star: the Sun. We all know that our year is defined by the time it takes the Earth to to make a complete journey around the Sun. But we could equally talk about the Sun’s apparent journey around the celestial sphere taking the Earth as our reference point. In astronomy, the tropical year begins at the vernal equinox point, which corresponds to the spring equinox, when day and night are of equal length. The tropical year lasts some 365.242 mean solar days or, expressed in more conventional terms, 365 days, 5 hours and 49 minutes. This imaginary solar voyage follows what is called an ‘ecliptic’ course. It comprises 360 degrees and is divided into the twelve houses of the zodiac. In relation to the celestial equator, an imaginary extension of the terrestrial equator, the Sun’s path runs at an angle of 23 degrees and 27 minutes. Under normal circumstances, the Sun enters the constellation of Pisces on 21 March. At this time, it finds itself directly above the terrestrial equator, such that the days and nights are of the same length. It then continues its journey in the direction of the northern hemisphere. At the beginning of Taurus, the Sun’s path crosses the celestial equator. Three months later, when it reaches the tropic of Cancer on 21 June, the Sun is at its maximum distance from the celestial equator. This point in the constellation of Gemini is called the summer solstice. Afterwards, the Sun directs itself again towards the south and the celestial equator. It crosses the latter on 23 September when it reaches Libra. The journey south in the direction of the tropic of Capricorn ends with the winter solstice on 21 December. At this time, the Sun enters into the house of Sagittarius before again setting out on its path towards the north and a new crossing of the celestial equator. The Sun reaches the latter around 21 March, when the spring equinox completes the tropical year.
In astronomy there are 88 constellations, of which only twelve bear the names of the signs of the zodiac. As any astrologer knows, there’s a big difference between the constellations and the signs of the zodiac. The constellations are simply groups of stars which are moving slowly west of the signs of the zodiac as established by Ptolemy in AD 200. Because of the precession, a minimal but constant shifting of the terrestrial axis, the Sun is now always to be found in the preceding sign of the zodiac. For instance, it is in Leo during the sign of Virgo. Eighteen hundred years ago the situation was quite different. When the signs of the zodiac were first given their names, the Sun was indeed to be found in the sign of the zodiac corresponding to that of the constellation of the same name. Thanks to the gyroscopic movement of the terrestrial axis, this will again be the case in around 24,000 years.
Future owners of a Reverso grande complication à triptyque can afford to ignore these astronomical niceties, however. In fact, their watch indicates at one and the same time the zodiacal calendar around the circumference of the dial and the position of the constellations in the aperture of the celestial horizon.
The Sun comes, the Sun goes away again
Days and nights of roughly equal length exist only at the equator. Everywhere else, they have different durations, except on the equinoxes of 21 March and 23 September. Because of the aforementioned ecliptic and the Earth’s elliptical orbit, the Sun rises earlier and sets later during the summer months than in the winter months. It’s common knowledge that the north pole remains untouched by the Sun’s rays for six months in winter while the Sun is busy lighting the south pole. Afterwards, exactly the opposite happens. And there are also the days when the Sun attains its highest or lowest point when it reaches the tropic. All these phenomena repeat themselves year in, year out. Beyond that, there exists an almost infinite variety of times at which the Sun is seen to rise and set; clearly, these alter from place to place.
The latter phenomenon consists of highly complex and detailed material that has traditionally been beyond the capacities of wristwatches to record: nothing is beyond the Reverso grande complication à triptyque, however. On its astronomical dial, two small hands illustrate the time at which the sun is due to rise and set each day. In order to be able to offer such information, each watch has to be regulated individually by means of a cam specifically calculated for the place of residence of its owner.
Equation of time
The movement of the Earth around the Sun describes an elliptical orbit. In addition, the Earth’s axis is slightly inclined. The upshot is that the lengths of true solar days vary. Between the longest and shortest days of the year, there is a difference of exactly 30 minutes and 45 seconds. Since such variations are ill- suited to the requirements of everyday human life, some ingenious minds invented the concept of mean time, which has 24 hours of equal length. This is what is shown on the front dial of the Reverso grande complication à triptyque. The difference between mean and true time, known as the equation of time, is at its greatest on 11 and 12 February (+14 minutes 24 seconds) and on 3 November (-16 minutes 21 seconds). Four times a year, on 15 April, 13 June, 1 September and 25 December, the mean and true solar days coincide exactly. On the Reverso grande complication à triptyque a cam takes account of these particularities. It is driven by the watch’s movement and completes one revolution per year. Its form physically represents the differences between mean and true time; another, no less ingenious mechanism detects the equation of time from the cam’s width at any given point and transmits its value to a hand crowned with a sun. The latter moves across a circle segment on the astronomical dial and allows the wearer to read the true moment of the solar zenith without having to bury himself in arid astronomic tables. Jaeger-LeCoultre is never satisfied with half-measures. It’s a question of honour.
In the carriage, a perpetual calendar
The Reverso grande complication à triptyque, a timepiece that specialises in astronomical phenomena, is a lot more than a standard wristwatch. One feature remains to be described. In addition to the true and mean solar time, sidereal time and sunrise and sunset times, it also has a calendar, a crucial function in our world. After a long search for a suitable location for it that would offer maximum legibility, Jaeger-LeCoultre’s team suddenly thought of the Reverso’s carriage. There are good reasons why the carriage has never been used before. In the first place, making a secure transmission between the pivoting case, in which the movement carries out its work, and the carriage is an extremely delicate task. However, once an objective has been defined, means to achieve it can usually be found. The key role here is played by an extraordinary system of levers which comes into action once a day. It is made up of three separate parts. The first is in the watch’s movement itself. It is continually activated by the hour wheel and has an autonomous barrel of its own. At precisely midnight, a lever descends into the notch of a snail cam. This instantly liberates the energy stored up in the barrel and enables it to release an actuator from of the case, which pushes back the upper tip of a lever in the support, and then activate another actuator in the carriage. The latter in turn acts on the ultra-flat calendar movement, barely 1.7 mm high, and advances the retrograde date, the day of the week, the month and the moon-phase disc by one position, instantly and simultaneously. Of course, the watchmakers have programmed the calendar in such a way that it knows the different length of each month up to the end of February 2100. Thus, for example, the date shown after 28 February 2007 will automatically be 1 March. But on 1 January 2008, a white letter B on a red background will appear, signalling that it is a leap year in which the month of February will have 29 days. The digital indication of the date possesses a charm all of its own. At the end of each month, it returns to its departure point in under a tenth of a second so that the days of the month can start their round again. Naturally, the case and the carriage must be properly connected at the moment of the date changeover at midnight. If they aren’t, nothing will happen. But there is no great danger in delay here, since an ingenious correction mechanism allows the wearer to carry out the change manually instead.
If you want to ensure that carriage and case are always properly connected at midnight, nothing could be simpler. All you have to do is activate a patented bolt mechanism which keeps the case in the correct position at the necessary moment before releasing it again afterwards. That way, all the lucky owner has to do is choose which dial should be face up during the operation.