As intangible as it may be, magnetism has long been renowned for its impact on the delicately adjusted mechanisms of precision timepieces. This was of little concern to the early watchmakers whose portable instruments, the most sensitive to magnetic fields, were initially so imprecise that their owners were unlikely to notice a deviation caused by the disturbing influence of a nearby object. It was not until the beginning of the 18th century that the impact of magnetic phenomena on the proper functioning of a mechanical movement was revealed in a quantifiable way, after the adoption of the steel balance-spring – invented by Christiaan Huygens in 1675-76. . – allowed a significant improvement in the precision with which pocket watches could measure time.
The first alloys
In this Age of Enlightenment, only sailors were able to observe the effect of compasses on marine chronometers and other deck watches. The problem was all the more important as these fragile instruments, which had to be protected from humidity, made their first sea voyages stowed with another equally important and delicate equipment: the ship’s compass. Watchmakers quickly realized that, like temperature variations, magnetic rays could misalign the carefully adjusted mechanism of a watch stored in the confined space of the officers’ quarters, or on the deck next to a watch. compass. The solution was to keep the stopwatch and the compass separate. Except that the world was heading towards greater industrialization. In the middle of the 19th century, the electric motor spread to all types of uses and equipment. In order to maintain the precision and reliability of their products, watchmakers have been forced to imagine an inexpensive way of effectively protecting movements from the disturbing effects of magnetic fields.
Until the 1930s and into the 1940s, most watches were fitted with bimetallic balance wheels and flame-blued steel balance springs, both of which were easily magnetized. One solution was to manufacture certain components not in traditional steel, which remains magnetized, but in alloys less sensitive to magnetic fields. The development of these ferro-nickel alloys was a first step in the right direction. Without being completely antimagnetic – magnetism is partly responsible for their elasticity – they had the advantage of regaining their regulatory properties when removed from the magnetic field, for the simple reason that these alloys do not remain magnetized. However, a more advanced solution had to be found for watches worn in a working environment exposing them to strong electric and / or magnetic fields.
Find a solution
During this period, watchmakers had found that a movement with a glucydur (beryllium-bronze) balance wheel and ferro-nickel hairspring required greater protection in specific environments, such as a cockpit, an electric locomotive or in factories. that used a lot of electric current. – motorized tools. They also noticed that watches with a dust cap were less prone to magnetization than others without this added protection. This has prompted some companies (including IWC with the Pilot and the Ingenieur, Rolex with the Milgauss and Omega with the Railmaster) to build highly specialized timepieces capable of withstanding magnetic fields up to 1000 Gauss by enclosing their movements in soft iron cages. This inner case – a sort of Faraday cage, since the dial was also made of soft iron – effectively protected the steel parts of the mechanism to maintain precise timing, even in the presence of strong magnetic fields.
If you can’t beat him …
These watches were at their peak in the 1950s and 1960s, when some brands began to take an interest in electromechanical movements – an innovation made possible after Mallory and Co. Inc. invented the button cell battery. At the time, the major difficulty was not to operate a watch by electrical, electromechanical or electronic means, but rather to provide it with a durable and above all autonomous power supply. Attempts had already been made: the first version was, by everyone’s opinion, a pocket watch built around 1910, which never made it past the prototype stage. It was only after the introduction of mercury batteries in the mid-twentieth century that it became possible to consider small self-powered devices. In an article published in the October 1955 issue of the Journal Suisse d’Horlogerie, AndrÃ© Beyner describes a wristwatch driven by a conventional mechanism associated with a micro-motor. According to Beyner, this watch had been in operation since December 1953.
Shortly after, in November 1956, LÃ©on Hatot, a French company specializing in electric and electromagnetic clocks, which it markets under the ATO brand, presented an electric wristwatch at the annual congress of the SociÃ©tÃ© FranÃ§aise de ChronomÃ©trie. Hatot’s watch was fitted with the first transistors and a Mallory mercury cell. He quietly sowed the seeds of a revolution that quickly took root in the United States thanks to Hamilton. Based in Lancaster, Pennsylvania, the American brand won its first victory in January 1957 by launching the first mass-produced electromechanical watch. Code name Project X, it gave birth to the future famous Ventura. Still present in the brand’s collections, the Ventura is now powered by a quartz movement, a logical evolution of the prototype which was regulated by electromagnets. Not to be outdone, in December 1958, the French firm Lip presented the R27, followed by the Lip Nautic-Ski – a project launched ten years earlier. Elgin, another American firm, played its part around the same time. The sales battle was on. This will be one of the most prosperous periods of mechanical watchmaking, until the launch in 1962 of the first Swiss electromechanical watch: the Conquest Electric Caliber 400 from Longines.