Armin Strom introduced the new Gravity Equal Force Ultimate Sapphire Purple. Full details and pictures. Price: CHF27,500
Launched by Armin Strom at the end of 2019 as the first automatic watch with a patented equal-force transmission integrated into the mainspring barrel (you can read our review here), the Gravity Equal Force returns in a new edition that combines a striking purple guilloché mainplate with an off-centred dial crafted from transparent sapphire crystal to display even more details of the sophisticated mechanics.
Limited to just 25 pieces per year in production, the new Armin Strom Gravity Equal Force Ultimate Sapphire Purple features a colour that Armin Strom has never used before. Its base plate boasts a guilloché-engraved motif with a barley grain pattern, expertly handcrafted in the atelier of acclaimed independent watchmaker Kari Voutilainen using a traditional rose engine lathe.
The striking purple colour is achieved using a 3D PVD process, which reflects a wide spectrum of tones as it shifts with the light.
The small grey-toned off-centred dial is crafted from transparent sapphire crystal, which is reserved exclusively for the Gravity Equal Force’s Ultimate Sapphire Editions.
It is completed by stainless steel hours and minutes hands crafted in-house and filled with super-LumiNova for enhanced legibility in low light environments. The small seconds sub-dial is positioned between 7 and 8 o'clock.
A triplet of dark grey ruthenium-plated bridges occupies the right-hand portion of the open display. They support the barrel in the lower part and the highly efficient unidirectionally winding micro rotor on top.
It takes up to an entire day to embellish by hand these bridges, inspired by the finger-style bridges found in pocket watches.
The barrel integrates a solution that helps transmit equal force - hence the name of the model - to the balance, thus increasing the consistency of rate. This solution pursues the same goals of complications like the fusée-chain transmission or the constant force escapement in a different way.
Inside the mainspring barrel, a stop-works declutch system operates to limit the torque delivered to the balance, thus smoothly distributing power.
More specifically, thanks to a Geneva wheel (aka Maltese cross) mounted to the barrel housing cover, the rotation of the mainspring barrel is limited to just 9 full turns out of a possible 12.5. This represents the central 72% of the mainspring’s potential torque curve, the flattest and most consistent portion. As the barrel housing unwinds around the arbor, a pin counts the rotations on the Geneva wheel until it reaches the locked position and prevents further unwinding.
On the caseback, the central inscription of the hand-wound ASB19 caliber notes that the movement was designed and manufactured in house by Armin Strom, adjusted in all positions and fitted with 28 jewels. The balance wheel beats at the frequency of 3,5 Hz (25,200 vibrations per hour) with an autonomy of 72 hours.
Through the transparent sapphire crystal case back, connoisseurs can appreciate other Haute Horlogerie finishes of the movement, such as the polished bevels (anglage) on the bridges, black polished screws, polished countersinks, perlage, and various types of graining—whether straight or circular—as well as Geneva stripes on the three-quarter bridge.
As with all Armin Strom watches, the Gravity Equal Force Purple’s movement is initially assembled to ensure it is in perfect working order and meets the brand’s exacting decorative standards. It is then disassembled and reassembled a second time when it is ready to be cased in its final form.
The Gravity Equal Force Ultimate Sapphire Purple is housed in a well proportioned stainless steel case that measures 41 mm in diameter, with its lines highlighted by the alternation of satin-brushed and polished surfaces. 12.65 mm thick, the case offers water resistance up to a pressure of 3 bar (approximately 30 metres / 100 feet).
Nicely paired with a light grey nubuck leather strap with purple stitching, the new Armin Strom Gravity Equal Force Ultimate Sapphire Purple, ref. AS/ID ST24-GEF.SA.AC.M.A7.FC, is priced at CHF 27,500. arminstrom.com
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