Watches: Arnold & Son Constant Force Tourbillon

By Thierry Ané on March 3, 2015

In watchmaking as in any other industrial sector, competition is fierce and in the current economic conditions brands have to struggle to retain market share, let alone increase it. This statement applies even more strongly to the Haute Horlogerie segment. The times when investment bankers and entrepreneurs were happy to relinquish indecent amounts of cash for any well-marketed supposedly innovative timepiece are long gone. Nowadays, watch brands have to somehow justify their six-figure price tags…


Some of them have embraced the high-tech path to successful sales. With the help of unheard-of materials and technology, they reinvent watchmaking and its traditional complications to wow watch aficionados with futuristic creations able to strike the sci-fi-loving chord we all kept from childhood and trigger irrational buying sprees. Richard Mille showed the way and niche brands like MB&F, Urwerk, or more recently HYT, have also adopted this recipe for success.


Most of the high-end brands, though, remain traditional when it comes to the design of their products and entice customers with the promise of timeless elegance. Although this may help justify the purchase, it certainly makes it even more difficult for a particular brand to stand out from its competition. Haven’t we, by definition, already seen all the traditional complications, sometimes even all at once in a timepiece? What can a brand offer in this context to catch the attention of wealthy collectors?


Lately, watchmakers came back to basics and have shown renewed interest for the pure chronometric performances of their top-of-the-range models. Competitions like the Concours International de Chronométrie have witnessed a regained interest and brands’ communication also appears to insist on the precision of their timekeepers, a notion that seems useless at the time of atomic clocks but that was critical when the best marine chronometers were built to help mankind explore the world.


Recently, in the search for ultimate mechanical precision, many players of the Fine Watchmaking segment have focused their research and development on constant force. Loosely speaking, to be accurate, the balance of a watch must oscillate at a constant rate and to do so, it requires no disturbance, especially not through the amount of energy it receives. Unfortunately, however, the force that powers a watch is intrinsically irregular! Indeed, a fully wound spring delivers a lot of energy but as it unwinds, the force it provides decreases sharply. In this context, how can we expect the balance to remain isochronous?


Considering their dedication to Fine Watchmaking and their history with marine chronometers, it was only a matter of time before Arnold & Son tackled this quest for higher precision with their own interpretation of the constant force mechanism. To this end, in Basel this year, the Swiss luxury brand will officially unveil the impressive Constant Force Tourbillon timepiece.


At the heart of this exceptional timepiece beats the brand new A&S5119 mechanical movement entirely developed in-house. This manually-wound calibre features a patented constant force device to provide a constant flow of energy to the balance and a tourbillon to also average out all gravitational errors and ensure together outstanding chronometric properties.


As always with this remarkable brand, the movement has been thought of to achieve its primary goal but also with aesthetic considerations in mind. The open-worked dial is a model of symmetry and outstanding finishing but also the perfect showcase for the ingenuous system it houses.




The upper part of the dial presents the source of the movement’s power, namely the mainspring barrels. Plural indeed as the watchmakers used two barrels in series. Visible at 10:30 and 1:30, they provide a beautiful symmetry to the watch’s design but also serve a technical purpose. Indeed, a single barrel powers the gear train and the second serves as a safety and tops up the first whenever its torque output drops below optimal, allowing for the most constant transmission of power possible to the regulator.


The lower part of the watch retains the same layout with two trapezoid-shaped bridges mirroring those of the barrels but this time holding the tourbillon cage at 4:30 and the constant-force mechanism at 7:30 also featuring the brand’s signature deadbeat second.


There are essentially three ways of providing constant force to the balance. One can use a fusée and chain system to compensate for the declining power of the barrel as recently seen on Zenith’s amazing Academy Georges Favre-Jacot model that I reviewed in FebruaryWatches: Zenith Academy Georges Favre-Jacot (+live pics). One can also redesign the escapement itself so that a precise amount of energy is supplied to each impulse of the balance. This is the solution followed by Girard-Perregaux and their utterly jaw-dropping Constant Escapement model.

The third and more common alternative, though, consists in creating a buffer store of energy in a remontoir. This is the solution adopted by Arnold & Son for the Constant Force Tourbillon: the mainspring barrels do not feed directly the escapement/tourbillon but rather charge a small hairspring. It stocks up energy and releases a consistent amount of power to the escapement/tourbillon at regular intervals. Since the frequency at which the remontoir releases the energy is a matter of choice, the brand opted for once every second so that the device could drive the true-beat seconds hand as a by-product.




Visually, the entire layout of the watch is perfectly symmetrical, both on a vertical and horizontal axis. The harmony is even strengthened by the fact that both the tourbillon cage and constant force device achieve a 360° rotation in one minute. The only difference being that the tourbillon’s cage sweeps constantly in this 60-second interval whereas the constant force device jumps by one-second increments to achieve its revolution.


The rest of the timepiece is pure Arnold & Son’s style: a magnificent 46 mm red gold case and a hand-stitched brown “bottier” alligator strap with patina finish as well as superlative decorations and Haute Horlogerie finishing on every single part of the movement (front and back)! Presented in a limited series of just 28 timepieces, the Constant Force Tourbillon is the perfect example of this young brand’s impressive dedication to Fine Watchmaking and a logical addition to the long list of exciting timepieces they have released in recent years.


In the traditional Haute Horlogerie segment, not only do they manage to impress by their technical achievements and chronometric performances, but they also succeed in refreshing the conventional design codes to offer absolutely outstanding creations. I truly look forward to bringing you back our own pictures and videos of this brand’s production for 2015!


For more information please visit the Arnold & Son web site.


For a technical description of the timepiece and additional pictures: