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Two hearts beat as one
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Two hearts beat as one

Tuesday, 21 February 2017
By Xavier Markl
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Xavier Markl

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4 min read

Christiaan Huygens foresaw it. Antide Janvier and Abraham-Louis Breguet made it happen. Resonance is a well-known phenomenon of physics, but only a handful of modern watchmakers have succeeded in applying it to their movements.

Resonance is a well-documented phenomenon in physics whereby a body responds when exposed to a periodic force that is very close to its natural frequency. A resonant system can be easily observed in a swing: the to-and-fro movement of the swing (its amplitude) only increases when it is pushed at regular intervals corresponding to its natural frequency. Similarly, strike a tuning fork and a second tuning fork next to it will begin to vibrate and produce a sound, provided both are tuned to the same pitch.

History tells us that in 1665, the Dutch scientist and mathematician Christiaan Huygens had taken to his bed, ill. While lying there, he observed a peculiar phenomenon: two pendulums hanging from a beam ended up swinging in exact opposite directions. No matter how many times he set them swinging again, they would synchronise, regardless of their starting position. Huygens suspected that the tiny vibrations transferred through the beam were the explanation for the “sympathy” between the two pendulums. Centuries later, science would confirm his intuition.

Armin Strom - Mirrored Force Resonance
Armin Strom - Mirrored Force Resonance

This phenomenon captivated horologists, although few were successful in applying it to the measurement of time. Antide Janvier (1751-1835) was the first, in the early nineteenth century, to experiment with resonance in his dual pendulum clocks. The earliest resonance pocket watches were made by the great Abraham-Louis Breguet (1747-1823). Closer to home, certain wristwatches have sought to take advantage of the synchronicity of two oscillators to achieve greater chronometric precision: a pas de deux in which variations or disturbances in the rate of one are offset by the other.

First into the fray was François-Paul Journe, who in 1999 presented his Chronomètre à Résonance, a wristwatch fitted with a double movement having two separate gear trains with two barrels and two regulators. They are laid out independently and symmetrically, with the exception that one of the two balance cocks swivels in order to finely adjust the distance between the two oscillators so that they will function “sympathetically”.

FP Journe – Chronomètre à Résonance movement
FP Journe – Chronomètre à Résonance movement

After working on synchronised clocks (H101 Resonance/Modern Double Regulator Clock in 2000), in 2005 Beat Haldimann presented the H2 Flying Resonance wristwatch, whose two balance springs are connected by a coupling spring inside a large flying tourbillon cage. The energy supplied to each oscillator is regulated and equalised by a remontoir d’égalité constant-force system.

Beat Haldimann – H2 Flying Resonance
Beat Haldimann – H2 Flying Resonance

Antoine Preziuso combines three flying tourbillons in his TTR3 TriTourbillon Resonance 3. They are mounted inside a large, mobile cage on a plate, at equal distance from its centre. This rigid plate, which is separate from the rest of the movement, is made in grade 5 titanium. It amplifies and transfers vibrations, thereby causing each oscillator to resonate with the other two and mutually compensate. A key element of Preziuso’s system is the triple differential, which equalises the respective rate of the three regulators to encourage them to stay in step with each other.

Antoine Preziuso – TTR3 TriTourbillon Resonance 3
Antoine Preziuso – TTR3 TriTourbillon Resonance 3

Towards the end of last year, another independent brand, Armin Strom, unveiled one of the most spectacular applications of resonance in watchmaking. Like Breguet’s pocket watches or François-Paul Journe’s Chronomètre à Résonance, Armin Strom’s Mirrored Force Resonance watch is fitted with a dual movement, having two identical and independent barrels, gear trains and regulators. As an added refinement, the twin oscillators are connected by a steel coupling spring attached to their stud. The brand spent more than two years studying the shape of this spring, which is made by electrical discharge machining with a five-micron tolerance, so that waves would be optimally propagated on a horizontal plane. The vibrations that are transferred via this spring – in exactly the same way they passed along the wood beam to Huygen’s pendulums – enable the two balances to beat in unison, at the unusual frequency of 3.5 Hz. It’s a wonderful sight to watch them synchronise, in less than ten minutes, to then oscillate in opposite directions and compensate each other’s variations in rate for better precision.

Armin Strom – Mirrored Force Resonance Calibre AFR15
Armin Strom – Mirrored Force Resonance Calibre AFR15

Multiple regulator watches are fascinating to behold. Even though differential systems (a set of gears that establishes an average rate) are often at the heart of these mechanisms, resonance is a no less complex and interesting solution. The idea of regulating organs answering each other like an echo has a poetic ring. Latest research into resonance is paving the way for some promising developments, if only the potential offered by high-tech materials in optimising the function of the springs that transfer vibrations between the balances.

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