With GREUBEL FORSEY certificate.
Robert Greubel and Stephen Forsey have been working together for nearly 20 years in a relationship founded on their shared technical creativity and quest for perfection.
In 1999 they began working on a new generation of tourbillon specifically designed to improve the timekeeping of the mechanical watch. Four years later they unveiled GREUBEL FORSEY and stunned horological aficionados with their innovative Double Tourbillon 30°, a timepiece clearly demonstrating their twin goals of innovation and excellence.
Robert and Stephen continue to build on their deep traditional knowledge gained with four decades of combined experience in high-end complicated timepieces, by inventing and developing technically valid horological complications to rigorous aesthetic principles.
Over two centuries ago, Abraham Louis Breguet invented the tourbillon as a way to equalise escapement errors inherent in watches of the day. The entire escapement was constructed in a cage that rotated around a central axis, usually at a rate of one revolution per minute. Later developments such as the carousel had the escapement mounted on a platform that rotated from six minutes to sixty minutes.
Whilst the tourbillon pocket watches made their mark as chronometers during the years 1850-1880, thanks to its appearance in wristwatches the device has remained one of the most prestigious complications of haute horlogerie.
The GREUBEL FORSEY DOUBLE TOURBILLON 30° is a creation that undertook more than four years of research and development. It features a tourbillon within a tourbillon, in such a way that this new complication permanently compensates the rate of gravity-related errors in all positions.
Named the Double Tourbillon 30°, due to the angle that links the two mobile cages, the patented double tourbillon system is a decisive technical advance and milestone in watchmaking history. Inside an exterior tourbillon with a diameter of around 15 mm. which turns in a four-minute period, an interior tourbillon, smaller in size and inclined at 30 degrees in relation to the first cage, revolves in 60 seconds. It contains the escapement, free sprung balance system with flat hairspring and Phillips terminal curve. A mark of its sophistication is the two cages which comprise 128 elements and altogether weigh a mere 1.17 grams.
The main characteristic of the invention is the 30-degree inclination of the interior of the interior cage rotation axis in relation to the rotational speed of the two tourbillon cages, creates the optimal conditions for the balance wheel to oscillate permanently in all positions. Thus, the compensation of the differences in rate due to the earth's gravity pull is no longer limited to the vertical position.
The choice of 30 degrees for the angle between the two turning carriages ensures a better chronometric performance whilst maintaining a perfectly acceptable depth to the watch. Furthermore, the exterior tourbillon's rotational speed of four minutes gives ideal mobility to the balance wheel by avoiding prolonged exposure to the earth's gravitational pull in less favourable positions.
The architecture of the movement within a diameter of 36.4 mm. is entirely dedicated to the presentation of the Double Tourbillon 30°. Its unconventional construction uses two plates so as to organise the gear-trains and bridges in a discrete fashion, leaving space for the rotation of the imposing cages. The plates and bridges are made of solid nickel silver, a traditional watchmaking alloy (copper, zinc and nickel).