Overview

Energy at the nanojoule scale

The Greubel Forsey Nano Foudroyante, from the Mechanical Nano collection, in white gold, 37.9 mm and 10.49 mm high — the brand's smallest case. A perpetual foudroyante beating six times a second inside the brand's first flying tourbillon, with a flyback 60-minute counter, on a manually wound movement of 428 components; 22 timepieces.

The Nano Foudroyante is the brand's tenth fundamental invention and the first watch of its Mechanical Nano collection. The idea is to manage a mechanism's energy at the nanojoule scale, which cuts both the number of parts and their size: 428 components, a movement 31 mm across in a 37.9 mm white gold case, the smallest the brand has built. The foudroyante is perpetual — it runs all the time — and sits inside the brand's first flying tourbillon, on a manually wound movement with a flyback function and a 60-minute counter. 22 pieces.

A foudroyante hand turns once a second, jumping in steps set by the balance frequency: at 3 Hz each oscillation gives two beats, six a second, so the hand divides the second into six. In a conventional movement the display costs about 30 microjoules a jump and needs its own gear train; here it draws 16 nanojoules, 1,800 times less, and the gear train is gone, the beat taken straight off the movement through a few low-inertia wheels. The mechanism is 90% smaller as a result. It sits in the flying tourbillon, and though the cage turns once a minute the foudroyante's own dial stays pointed at twelve o'clock so it can be read. The flyback and its 60-minute counter are under column-wheel control, and the reserve is 24 hours.

Key details

Design and engineering

• NanomechanicsEnergy inside the movement is managed at the nanojoule scale. The brand's account is that this, not smaller parts, is what cuts consumption and component count.
• Perpetual foudroyanteSix jumps a second from a 3 Hz balance, running continuously; 16 nJ a jump against a conventional 30 μJ, with no dedicated gear train.
• Flying tourbillon with oriented dialThe brand's first flying tourbillon, turning in 60 seconds, carries the foudroyante; the small dial stays aligned to twelve o'clock as the cage rotates.
• Flyback with column wheelA 60-minute counter and flyback under column-wheel control, on manual winding.
• CaseWhite gold, 37.9 mm and 10.49 mm high, water-resistant to 30 m — the smallest Greubel Forsey case, around a 31 mm movement.

Movement

• Manual winding; flying tourbillon with Nano Foudroyante, 60-second rotation; hours, minutes, small seconds; 60-minute counter, flyback
• 428 components; movement diameter 31 mm
• Foudroyante energy 16 nJ per jump; mechanism volume reduced by 90%
• 21,600 vibrations per hour (3 Hz)
• Power reserve 24 hours

The reference

Technical specifications

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Greubel Forsey · Tourbillon