The Test of Time: ICC
By Timothy Treffry
The International Chronometry Competition, based in Le Locle, is calling for entries for 2013. Unlike other chronometer certifications, such as COSC, which are simply pass/fail tests that the overwhelming majority of entrants pass, this is a competition, something of an assault course, with winners and losers. QP takes a closer look at the event and its requirements.
François-Paul Journe, an enthusiastic participant in the biennial Le Locle competition since its inception in 2009, told QP: "I am pleased that a genuine chronometry competition emphasising precision, and not a media-focused competition linked to product purchases, has come back to life. We should return to the old custom of observatory competitions giving a gold medal to the winner, followed by silver for second and bronze for third." The historic chronometer tests referred to were conducted by some European national observatories in the 19th and much of the 20th centuries, but disappeared with the advent of quartz movements in the early 1970s. Japanese watches began to win all the prizes; the Swiss solution was to boycott the competitions and they were subsequently abandoned.
The watches are put under various high-tech tests by COSC and monitored daily.
The International Chronometry Competition (ICC) is open to any watches made and adjusted in Europe, which are for sale to the public, whether made by individuals or brands. There are separate categories for tourbillons and those with fixed escapements. There is also a category for students who must assemble and adjust a given proprietary movement. The rate of each watch; the amount it gains or loses each day under different conditions, is tested according to the chronometer test of the International Standards Organisation, ISO 3159, the same standard used by COSC (see box).
Unlike a clock that just sits on a shelf, a wristwatch has to maintain its rate whatever the orientation of its owner's wrist, in hot or cold weather. COSC tries to mimic this, but the ICC is rather more demanding. COSC tests stripped-down movements, but ICC deals with cased watches that are ready for sale; rates are checked with any complications, such as calendar mechanisms, which periodically take energy from the movement, in place. Watches are also rated before and after exposure to magnetic fields (ISO 764) and a number of shocks. A rather scary video of the 'shocking machine' can be seen on the ICC website.
Multiple examples of the same watch are collected by COSC to fairly test their accuracy.
But it is ISO 3159 which is at the heart of the competition; each watch has to go through it three times: once at the Besançon Observatory, again at the Bienne office of the Swiss Chronometry Inspectorate (COSC) and for a third time when it returns to Bienne after the magnetic-field and shock tests are administered at the Advanced Engineering College (HE-Arc) in Le Locle.
The essence of ISO 3159 is that the rate of the watch is checked 'in positions' and at a range of ambient temperatures. But what is the significance of position and temperature? Accurate timekeeping in a mechanical watch requires that the balance precisely maintains its designed frequency of oscillation, most commonly 4Hz (28,800vps). In QP54 (Overcoming a Taboo) we mentioned that a balance swings more freely when it is horizontal than when it is on edge; this is the first problem for the watch designer. The next problem is the rate in 'the edge positions'. When it is spinning on edge, just like the wheels of a car, the balance should be just that, 'balanced'.
It's easy enough to balance (or poise) a balance wheel, but when considered in combination with a balance spring in a working watch, the task becomes almost impossible. One end of the spring is attached to the balance staff and the other is fixed to the watch plate via the balance cock. As the balance swings back and forth, the mass of the spring (or to be right up-to-date, its Higgs bosons) are redistributed unevenly around the balance staff so that the centre of gravity is, at best, only briefly at the centre of the balance staff. The centre of oscillation will be biased towards where the centre of gravity is at its lowest point.
The Tissot Le Locle was the best of the 'Classique' category in the 2011 International Chronometry Competition.
And then there is the temperature problem: if the balance wheel expands and contracts as the temperature changes, its moment of inertia will change (those bosons again). Temperature changes can also affect the elasticity of the balance spring. Here, science came to the rescue with the invention of special metal alloys whose response to temperature change is very low - the inventor got a Nobel Prize.
The problem of the moving centre of gravity remained until watch adjusters learned how to bend the ends of the balance spring so as to make it 'breathe' more evenly (the Breguet overcoil is only one example, other 'terminal curves' are flat). Some errors remained, but adjusters can endeavour to move them so that they are only expressed in the edge position when the 12 is uppermost - an orientation in which a wristwatch rarely finds itself and which is not tested.
The ICC takes the rates from COSC tests and plugs them into a formula that weights the variations according to their importance. When tested, each position is maintained for two days. The average variation in rate when the position is not changed is most heavily penalised by being multiplied by 55. The average variation between changes of position is multiplied by 45, the difference in rates between the vertical and horizontal positions by 33.3, the greatest variation by 20, the average daily rate by 12.5 and the greatest difference in rate overall by 10. The temperature variation is multiplied by 500, but it is a small number so the effect is not overwhelming. These values are subtracted from 1,000, giving a final score for each watch.
Greubel Forsey's Double Tourbillon 30° Technique was the winning tourbillon - and indeed the highest scoring watch - of last year's competition.
The first two competitions were won by tourbillons. This is scarcely surprising as Breguet's reason for the original tourbillon was to eliminate variations in the edge positions. An inclined tourbillon will be relatively indifferent to all changes in position. In 2009, Jaeger-LeCoultre was the overall winner with its calibre 978 Master Tourbillon scoring 909 points. The competition clearly favoured tourbillons, so in 2011 they were placed in a separate category from standard escapements. The winning tourbillon was Greubel Forsey's Double Tourbillon 30° Technique (an inclined tourbillon) with 915 points. The best of the watches with the traditional fixed escapement was a relatively humble Tissot Le Locle Chronometre Automatique, with 764 points.
It is clear that the ICC is a challenging test; in 2009 only 10 of 16 entrants completed the course, in 2011 just three of the six tourbillons gained a classification and two of seven fixed escapements. Those failing to be classified either had rates falling outside one or more of the ISO 3159 criteria in one of the three tests or stopped. Stopping during the tests, which many did, was frowned upon.
This is clearly a much more demanding test than the classic COSC. Although the organisers list all the watches entered, to spare the blushes of the less successful, they only identify the results of the top three qualifiers in each category. Those interested in the skills watchmaking requires must admire the courage of all those entering the ICC 2013, look forward with interest to the announcement of the results, and perhaps ask themselves why so few brands participate; preferring 'brand ambassadors' to performance when promoting their watches.
Further information: www.concourschronometrie.org