In principle at least, a gentleman can drop his mechanical watch, take it for a dip, or inadvertently treat it to a Turkish bath without any unwelcome consequences on its functioning. This hasn’t always been the case. What we now take for granted is the end product of a long quest for excellence. Whether in terms of materials, parts or mechanisms, watchmaking has, from its earliest days, sought to improve the composition and construction of its movements. Thanks to slow and steady progress, we can now wear our watch in all circumstances, including the most extreme conditions, without worrying about any adverse effects this will have on its precision. This is quite an achievement, knowing that a round of applause corresponds to a shock of 150 g, i.e. an acceleration of 1,470 metres/second then a sudden halt, several times in a row. The fifteenth Study Day hosted by the Société Suisse de Chronométrie (SSC) on September 20th in Montreux chose Reliability and Robustness as its theme to trace “the precise measurement of time over time.”
A brief history
While tests and standards may be a modern affair, watchmakers quickly made it their business to improve their mechanisms’ functioning. Movements, initially in iron, soon switched to steel (iron combined with 0.3 to 2% carbon by cementation). Brass went some way toward resolving the problem of wear caused by friction, with further progress as of 1704 with the introduction of jewels which are still used today, albeit synthetic ones. “The technique for drilling sapphire was developed in England,” explains Arnaud Tellier, a specialist in antique horology and founder of Tellier Fine Arts. “This closely guarded secret put the English at the forefront of precision watchmaking in Europe for a very long time.” Gold and platinum, both high-density metals, also appeared in movements, particularly to make balance wheels and oscillating weights.
At the same time, metal workshops were developing techniques such as firing and quenching that would distinguish their production. This technology paved the way for later alloys, specific to watchmaking, such as Invar and Elinvar. Their low coefficient of thermal expansion made them the ideal material from which to make balance springs, invented in 1675 by the Dutch scholar Christiaan Huygens. His innovation gave rise first to pocket watches then wristwatches.
Now, as in the past, watchmakers are pouring every effort into increasing precision, and in this respect silicon is symptomatic of the current state of research. However, some studies recommend abandoning the Swiss lever escapement and its good old balance spring altogether, in favour of magnetic oscillators. Both TAG Heuer and Breguet have been thinking along these lines, although the star of the Study Day proved to be De Bethune whose horological résonique, which founder Denis Flageollet is proposing as a new branch of study, may be one of the most promising breakthroughs in this field. An audio-frequency oscillator (between 20 and 20,000 Hz) combined with a magnetic escapement – a magnetic rotor which, as it rotates, transfers energy to the oscillator – could be the key to significant gains in efficiency and regulating performance.
The first prototypes should be ready within the coming months, followed by the obligatory resistance tests. Indeed, a watch, when worn, is subjected to countless stress factors. Of these, shocks have the biggest impact on precision. The first measuring devices date from the 1940s while the first data was published in the 1960s. This gave rise to the NIHS 91-10 standard, drafted by the Federation of the Swiss Watch Industry, followed ten years later by the ISO 1413 standard. Both define minimum shock-resistance requirements, including resistance to an accidental fall from a height of one metre onto a hardwood surface.
Studies have resulted in tests which simulate, at an accelerated rate, the mechanical constraints on a wristwatch when worn. Equipment and procedures have been developed by brands and independent laboratories. The best-known protocol, Chronofiable, was introduced in the late 1970s by Laboratoire Dubois in La Chaux-de-Fonds. It accelerates the watch’s ageing process by a factor of four to eight. During the last cycle, over a period of 21 days the watch is subjected to 20,000 shocks ranging from 25 to 550 g, linear and angular accelerations, and variations in temperature and humidity corresponding to six months of wear.
Some observers, however, are contesting the continued relevance of standards drafted more than 40 years ago. Rolex, for its part, has decided to conduct an experimental study to implement, in laboratory conditions, repeatable shock tests that correspond to real-life conditions. Parameters have been chosen to this effect, for example adding carpet and tiles to the hardwood surface of the ISO 1413 standard. The Association Suisse de Recherche Horlogère (ASRH) is also keen to dust off old tests. The “Porter 2015” project it recently submitted to its 150 members proposes a full review of test criteria. “Certain things have changed over a generation,” comments Fabienne Marquis, director of ASRH. “Gravitation is the same but materials, the electromagnetic environment and pollution, for example, are all new factors. We want to be sure that tests still correspond to the reality of today.”
Article published in WtheJournal.com