Breguet's "Queen of Naples" watch, a poetic expression of innovation, and the mystery of its supple hands

Traditionally, watch hands have been rigid and move in perfect circles. For this reason, from the early days to the present, most watches have used round cases. However, there is another shape that is close to round but is even more elegant and delicate: the oval. So how can you create the perfect hand movement for an oval case? Breguet found a beautiful and innovative answer to this question. The result is the heart shape adopted for the Reine of Naples 9825 "Heart Edition".

Breguet found the perfect hand movement for the oval case

　Technological innovation is not always visible to the wearer of a watch: it is often hidden within complex mechanisms, alloys, or production methods, but in the case of the variable-length hands of Breguet's Reine de Naples 9825 "Heart Edition," they unfold before our eyes in a graceful and captivating way.

　The choice of the oval shape was always limited by the geometric impossibility of making the minute hand follow the contours of the case, and it is clear that the key to achieving this is an elastic hand that can change length to follow the egg-shaped shape of the watch.

　There are solutions. For example, Parmigiani Fleurier's "Oval Pantograph" was inspired by an oval pocket watch that the brand restored. Its elastic hands use the mechanics of a pantograph: two parallelogram-shaped structures, like a telescope, follow the oval shape of the dial as they move. The construction is a delicate rendition of a mechanism said to have been inspired by Eiffel.

　The solution developed by Breguet for its beautiful oval Reine de Naples watch was completely different: its flexibility comes not from connecting rigid parts, but from flexibility and elasticity.

The birth of "Queen's Heart"

The minute hand of the Reine of Naples 9825 "Heart Edition" is a testament not only to its scientific and technical aspects, but also to the beauty and delicacy that this flexible appendage brings to an oval-shaped watch. The Reine of Naples timepiece is said to have been inspired by the first watch designed to adorn the wrist of the Queen of Naples. The tiny heart that expands and contracts to indicate the hours is not only a beautiful and poetic achievement, but also a watchmaking feat.

　But behind this heart is an army of "surgeons" responsible for the concepts, calculations, materials research, testing and prototypes that allow the minute hand to breathe as it traces the oval shape of the watch.

Development of "curved bearings"

　The theory behind this is based on the famous curved bearing (invented in 2001 by the Instant-Lab laboratory at the Swiss Federal Institute of Technology in Lausanne, led by Professor Simon Henin), whose development led to many innovations, particularly in the regulation mechanisms of watches.

　The curved bearing now used in the variable length needle offers a visual and visible solution to a technical problem.

　The needle is made using the LIGA process using a nickel-phosphorus alloy, which is flexible, resistant to bending, and highly stable. The heart-shaped tip is fitted with two blades, each with a flexible and rigid section. The entire needle is extremely delicate, with the flexible section being only half the thickness of a human hair.

Two mechanisms move one hand

　Now that we've given the hands flexibility, we need to make them move. This is the most complex part of the puzzle. To advance the hands and change their shape and length, each arm must move independently. The clock movement moves the hands by rotating them through a set angle via the cannon pinion. Another plate mechanism changes this angle, changing the angle between the rotation of the hour wheel on the right arm and the rotation of the hour wheel on the left arm.

　Let me share with you the complex calculations required to accurately display the time. This involves the deformation and lengthening of the hands themselves as they follow the curve of the oval edge of the dial. In addition to calculating this equation, it is also necessary to take into account that the hour wheel rotates at an inconsistent speed.

Drive mechanism

　Breguet's designers and watchmakers considered several different mechanisms for moving the hands. One of these, a double non-circular gear train, was quickly tested and prototyped. While this prototype met the specifications, providing a simple, robust, accurate, and functional solution, the idea (currently patent pending) was shelved due to the inherent limitations of a non-circular gear train. Concerns about the "adjustment of the angular variation of the hand arms" could lead to unexpected changes, leading to the conclusion that a "non-circular" gear train would be too extreme.

　Another problem with this non-circular gear train is that it is not easy to improve or adapt. To drive it, a "system with a rotating post with an integrated cannon pinion" was required (Editor's note: this cannon pinion controls the movement). With each rotation, this post drives two cannon pinions, fixed on either side of the hands. The arm is connected to a planetary gear that contains a sensor, which interacts with a cam, the only fixed element in the assembly.

　The system, simple, robust, and relatively easy to assemble, features a small number of components, can be modified by simply changing the shape of the cam, and has passed all homologation tests for final approval. Two patents are currently pending. Breguet worked on this project together with Nivarox, Aslab, and ETA, a member of the Swatch Group.

　The delicate elegance of this particular hand evokes not only admiration but also a wealth of emotion, demonstrating that technical innovation can also produce something poetic.