The Watch Glossary - The Micro-rotor
History in brief, and some examples.
The micro-rotor is a refined technical solution usually available on luxury and high-end mechanical watches. When I talk about luxury watches with a micro-rotor, I mean sports or classic luxury watches whose price tag is at least ten to twelve thousand euros high (e.g., the Bulgari Octo Finissimo). It is indeed hard, yet not impossible, to find a luxury timepiece equipped with a micro-rotor based winding mechanism priced below this threshold.
Who invented the micro-rotor?
The original patent of the micro-rotor winding mechanism belongs to Universal Geneve, who filed it in 1955. According to other sources, it seems the system was patented by Buren in 1954 instead. However, this proves how the watchmaking community was eager to find, back then, an option capable of matching the pros of a manual winding movement, like a reduced case thickness, for example, with the advantages of an automatic wound movement. In a timepiece featuring a micro-rotor, the oscillating weight is placed into the mechanical movement. Aesthetically, it does not cover therefore gearings and decorations, as that's often the case with a standard winding rotor usually placed above the movement's bridges. Given its reduced size, a micro-rotor requires additional effort during the design phase, to ensure mass inertia and winding efficiency are guaranteed.
Which brands are currently adopting the micro-rotor winding mechanism? Here are some examples.
The first brand that comes to my mind is Piaget. It is probably the brand that offers the broadest range of high-end movements featuring a micro-rotor. Most of Piaget's collections adopt this technical solution, and, as that's the case with some skeletonized Altiplano models, the small winding mass is fully visible through the dial too.
A perfect example of Piaget's expertise in this regard is the Piaget Altiplano 60th Anniversary, released in 2017, that proves once more how the brand extensively adopts this solution to produce their ultra-thin watches. Another great example, in the industry, is the Regulator with Annual Calendar by Patek Philippe, which utilizes an off-centered 22-carat gold micro-rotor.
Finally, let me mention two new cutting-edge timepieces equipped with a micro-rotor: the former is the Roger Dubuis Excalibur Spider; the latter is the multiple award-winning Bulgari Octo Finissimo: the BVL138 caliber adopts a fine and very thin micro-rotor crafted in platinum.
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(Photo credit: Peter Tung for Horbiter®)
Gaetano C @Horbiter®