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High-Frequency Movements – Part I

HIGH FREQUENCY – HIGHER-BEAT WATCHES


When thinking about the features that watch aficionados want more, design, functions or complications immediately comes to mind... the rate at which a mechanical watch beats might be something to look into too. High-frequency movements remain a relative rarity but have much to offer.



THE BASICS: Is a movement’s frequency higher the better?


The wonder of mechanical timepieces owes much to their ability to measure time precisely. At their heart, the time is provided by an oscillator beating at a certain pace. A watch's frequency is determined by the number of oscillations its regulating organ performs over a period of time. It is typically measured in Hertz (Hz) or Vibrations per Hour (vph); one oscillation translates into 2 vibrations or beats. From a precision standpoint, it is widely considered that the higher the frequency, the better since these are less affected in case of shocks or perturbations.

With their quartz oscillator vibrating at 32.768Hz (the industry-standard frequency), quartz watches are far more precise than mechanical watches. A 'standard' atomic clock is probed by microwaves with a frequency of about 9.2 x 109 Hz. But speed is not everything; there are many other parameters that influence the precision and rate accuracy of a mechanical watch. A well-regulated, slow-beating mechanical mechanism can ensure excellent timing (relatively speaking, of course). Stability over time and controlling the different elements that can disrupt the mechanism and its regularity are essential. Friction, gravity, temperature changes, magnetism, the waning power delivered to the regulator and many other factors can affect the accuracy of a watch.



HIGH FREQUENCY MOVEMENTS: Movements beating at 5Hz / 36,000vph and Above With Over 200 Years History


Most modern mechanical watches are regulated by a Swiss lever escapement and a balance wheel running at 3Hz / 21,600vph or 4Hz / 28,800vph, which is often regarded as the best compromise to achieve sufficient accuracy without having to deal with the difficulties of crafting high-frequency movements. We usually refer to high-frequency movements as those beating at 5Hz / 36,000vph and above.

The concept of high-frequency movements is not new. For instance, as early as 1815 / 1816, Louis Moinet crafted his Compteur de Tierces to time the passage of the stars with precision. Believe it or not, his movement was running at an incredible 30Hz! High frequency was mainly used for precision timekeepers or stopwatches. By 1916, Heuer, Longines and Minerva were crafting 50Hz stopwatches capable of displaying 1/100th of a second. When it comes to wristwatches, high frequency really became a topic during the late 1950s and 1960s. In 1959, Longines introduced the calibre 360 (5Hz) for observatory trials. Although this movement was not intended to be commercialised, it performed exceptionally well at the Neuchâtel Observatory competitions.



SERIAL-PRODUCED HIGH-FREQUENCY WRISTWATCHES


Soon after, high-frequency watches hit the market with Girard-Perregaux in 1966. Marking a first, the Girard-Perregaux serial-produced Gyromatic HF was submitted to the Observatory trials. Girard-Perregaux and FAR (Fabriques d'Assortiment Réunies – the manufacturer of the balance wheel and escapement) were awarded the Centenary Prize of the Neuchâtel Observatory for their achievement! In the following months, Seiko, Longines and Zenith (with the El Primero in 1969) also launched high-frequency watches.

With the more recent renaissance of mechanical watchmaking, the interest in high-frequency mechanical movements has been reawakened. The concepts developed go beyond the use of a traditional balance wheel, hairspring and Swiss lever escapement and often rely on modern, lightweight materials such as silicon. Here are a few notable examples.



TAG HEUER AND HIGH FREQUENCY


In the early 2000s, TAG Heuer developed an impressive series of high-frequency concepts. In 2008, the brand released the Calibre 360, a dual-architecture chronograph (more about this in the second part of our article) with a 50Hz frequency for the chronograph. Presented in 2010, the TAG Heuer Pendulum was regulated by a 6Hz magnetic oscillator. The 2011 Mikrograph was another dual-architecture chronograph with 50Hz for the chronograph. Also presented in 2011, the Mikrotimer Flying 1000 had a dual-architecture chronograph with a 500Hz frequency for the chronograph thanks to a patented high-frequency spiral. TAG Heuer's research culminated with the 2012 Mikrogirder, which featured a vibrating linear oscillator (versus a classical balance wheel and hairspring) that vibrates isochronously at a very small angle. Unaffected by gravity, the system frequency has been pushed to an astonishing 1,000Hz!



MAGNETIC PIVOTS -THE BREGUET CLASSIQUE CHRONOMÉTRIE 7727


Introduced in 2014, the Breguet Classique Chronométrie 7727 ticks at a frequency of 10Hz or 72,000vph. To craft this high-beat movement, the brand developed a regulator with a silicon hairspring and escape wheel. Most surprisingly, the balance wheel rotates between 'magnetic pivots'. Virtually 'floating', the balance wheel is maintained in artificial gravity and is no longer affected by changes of position, ensuring a precise rate in every position. This innovative, friction-free mechanism was also instrumental in achieving the high frequency.



THE FREDERIQUE CONSTANT MONOLITHIC


Presented in 2021, the Frederique Constant Monolithic does away with a traditional balance wheel and Swiss lever escapement. Instead, it is regulated by a monolithic flexure pivot oscillator that integrates the escapement's anchor.

The revolutionary design oscillates with a low amplitude of only 6 degrees (versus ~300 degrees for a regular balance wheel). It runs at an impressive frequency of 40Hz or 288,000 vibrations/hour!

The Frederique Constant Monolithic is not the first high-frequency flexure oscillator relying on compliant mechanisms. If the Zenith Defy Inventor concept (15Hz) comes to mind (both concepts were developed in cooperation with a Dutch company called Flexous), the Monolithic oscillator incorporates several innovations concerning its design and geometry. The escapement anchor is incorporated into the oscillator, and, for the first time, this function is integrated into the flexures. This enabled a substantial reduction in size - in line with the footprint of a traditional balance wheel



DE BETHUNE RÉSONIQUE RESEARCH


In 2011, De Bethune's mastermind, Denis Flageollet, unveiled his fundamental research in the field of Résonique. The principle is based on a mechanically driven oscillator consisting of a magnetic rotor paired with magnets on an acoustic resonator. Positioned at the end of the gear train, the rotor makes the resonator vibrate. In turn, the rotor's speed synchronises with the resonator's natural frequency. De Bethune reports that working prototypes have been pushed to frequencies of up to 928Hz without friction or wear on the mechanism's regulator!


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