In the November 2022 issue, marking the 100th anniversary of the birth of the automatic watch, the Chronos Japan editorial team took a serious look at the automatic winding mechanism. We are republishing that page on webChronos. This time, we will be looking at the micro-rotor and peripheral rotor of the Bvlgari Octo Finissimo.
Interview and text by Masayuki Hirota (Chronos-Japan)
Edited & Text by Chronos Japan Edition (Yukiya Suzuki, Yuto Hosoda)
[Article published in the July 2022 issue of Kronos Japan]
Micro rotor vs. peripheral rotor
Two thin rotors set a new world record for thinnest watch
Bulgari has pushed the boundaries of thinness with the Octo Finissimo. However, what is even more impressive than its thinness is the variety of automatic winding mechanisms, including both micro-rotors and peripheral rotors.
First released in 2017, this ultra-thin movement features a micro-rotor and reverser-type bidirectional automatic winding mechanism. In 2022, the automatic winding mechanism was revamped, adopting a closed barrel and improving the escapement and balance. This masterpiece embodies Bulgari's technological prowess. Diameter: 36.60mm, thickness: 2.23mm, 31 jewels, 21,600 vph, power reserve: approximately 60 hours.
Bvlgari has rewritten the record for the thinnest mechanical wristwatch with the Octo Finissimo, which is supported by a micro-rotor and a peripheral rotor automatic winding system that places the rotor on the outer periphery of the movement.
Bvlgari explains that the Octo Finissimo first adopted a micro-rotor because the movement's large size allowed it to be incorporated without affecting thickness, and peripheral rotors had not yet been fully developed at the time. The design, which enlarged the baseplate and aligned the movement's components in a parallel arrangement, was well suited to a micro-rotor. Additionally, by leaving ample space for the automatic winding mechanism and weakening the mainspring, the BVL138 achieved a high winding efficiency that was unusual for a micro-rotor.
Normally, micro-rotors and peripheral rotors use unidirectional winding because their low specific gravity means that they may not be able to fully wind in both directions. In contrast, Bvlgari uses a switching rocker for its masterpiece, the BVL191, and a reverser for its micro-rotors and peripheral rotors.
First released in 2019. This movement is the world's thinnest automatic chronograph with GMT function. The key to this is the peripheral rotor, positioned around the outer edge of the bridge. The automatic winding mechanism uses a bidirectional reverser. Diameter: 37.20mm, thickness: 3.30mm. 37 jewels. 28,800 vph. Power reserve: approximately 55 hours.
Bvlgari now only uses reversers that have been approved after rigorous testing, and by conducting accelerated testing for up to 1.5 months, they confirm that performance remains unchanged even after five years of actual use. The company does not disclose the reason, but it may be that they disliked the spinning that comes with unidirectional winding. The feel of a luxury watch is one of the directions Bvlgari is aiming for. The manufacturer's capabilities are reflected in their automatic winding. With several excellent automatic winding mechanisms, the company is now one of the world's leading watch manufacturers.
