When you think about how watches are made, what comes to mind? Do you think of watchmakers wearing lab coats and loupes, meticulously polishing a part before adding it to a movement? Or do you think of nanofabrication engineers in cleanrooms, precisely adjusting plasma density to etch a part from a silicon wafer? It is a bit of both with the Ulysse Nardin Anchor Tourbillon, and that is a very good thing. The use of silicon in mechanical watches is becoming more and more popular, as brands are realizing the advantages the material brings to a mechanical watch movement. Silicon is anti-magnetic, extremely hard and lightweight, requires no lubrication, and can be manufactured to a level of accuracy previously unheard of. (Think in terms of nanometers rather than microns.)
Ulysse Nardin is a pioneer in the development of silicon technology for watchmaking. In 2000, the brand introduced its Dual Direct Escapement featuring silicon escape wheels. The Anchor Tourbillon takes silicon in watchmaking a step further, by building a mechanism that would have been virtually impossible to manufacture with any other technology. This is what makes this watch so appealing – it is a massive technological exercise that took years to develop. Rather than focus on duplicating existing parts in a movement with silicon, Ulysse Nardin (along with Sigatec, which they co-own) developed something completely new that significantly improves timekeeping.
So what exactly makes the Anchor Tourbillon so intriguing? The Anchor Tourbillon features a pallet fork with no pivots. Yes, you read that right – the pallet fork is suspended in between the escape wheel and balance roller with ultra-thin silicon blades. These blades buckle back and forth, allowing the pallet fork to perform its locking, unlocking and impulsing actions without a pivot. Not having a pivot means fewer parts, and no need for lubrication. I spoke with Stéphane von Gunten, Ulysse Nardin’s Manager of Research and Development, to find out more.
HODINKEE: Where did the idea to suspend the pallet fork on blades originate from?
Stéphane von Gunten: The guidance of the classical anchor through its two pivots rotating into small jewels was always a delicate topic in the watchmaking history. The pivots are not lubricated and it can sometimes lead to material wear over the years of function of the watch. There is also a little play [gap] between the pivots and the hole of the jewel which can produce small inaccuracy in the escapement. The original idea of the Ulysse Anchor was to suspend the whole anchor on two thin blades to reach a perfect positioning system [zero gap] thanks to this virtual pivot and to avoid any risk of material wear [zero friction].
HODINKEE: How thin are the blades?
Stéphane von Gunten: The blades have a thickness of 15 micrometers and are 4 mm long. This aspect ratio is made possible only thanks to the silicon micro-machining technology of [a process called DRIE for Deep Reactive Ion Etching]. The blades are completely straight over the length of 4 mm, as the precision in the geometry is better than .5 micrometers.
HODINKEE: How are the upper pallet fork and lower pallet fork attached?
Stéphane von Gunten: The two levels are fixed together by our watchmakers with the use of two small rivets that have a diameter of about .4 mm.
HODINKEE: Why did the shape of the escape wheel teeth change from earlier versions?
Stéphane von Gunten: The [latest] version of the Ulysse Anchor Escapement is a so-called constant escapement. This particularity allows the balance wheel to get the same amount of energy, so the same amplitude, all through the discharge of the main spring. It helps to get constant frequency of oscillations in an independent manner of the torque delivered from the main spring. The energy is given from the blades and the escape wheel is now used as a “recharger” of the blades that comes after each impulse to the balance wheel. It was not the case in the first version of the Ulysse Anchor Escapement. It is for this technical reason that the geometry of the wheel has been slightly adjusted by our engineers.
HODINKEE: What do the notches on the periphery of the pallet fork bridge do? Are they to adjust tension on the blades?
Stéphane von Gunten: Exactly. These two levers are used to put the blades in compression. With the right compression the system becomes bi-stable. By switching from one stable position to the other, a small amount of energy is given to the balance wheel at each alternance [vibration].
HODINKEE: Is there any functional benefit to having different thicknesses of silicon oxide deposition on the pallet fork and escape wheel?
Stéphane von Gunten: The utility of the [silicon] dioxide layer is to have a low frictional coefficient between the wheel and the pallets. It also induces no risk of material wear [no abrasion]. A minimum thickness is required for the technical properties of the parts, mainly to have a low frictional coefficient. Depending on the part and its dimensions the aesthetics, color of the part, can be influenced by the thickness of the oxide layer [diffraction of light into the silicon dioxide layer]. Small variations of colors could also happen depending on the direction of the light to the objects.
With the all-silicon escapement in its one-minute flying tourbillon, you really have a mesmerizing mechanism. As the tourbillon rotates the silicon reflects light in a beautiful way, with different colors depending on the amount of oxide deposition for the individual parts. This watch is an exercise in both traditional and futuristic watchmaking, and the result is evidence that mechanical watches have tons of room to continue to innovate.
For more information, visit Ulysse Nardin's website.
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