Ferdinand Berthoud FB 2RE.2, Rose Gold

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This is one of 10 examples of the Chronométrie Ferdinand Berthoud FB 2RE.2* with a 44mm rose gold case and two-part black enamel dial. Introduced in 2020, the reference was the first example from the resurrected name to feature a conventional time display. The aesthetic borrows inspiration from the pioneering watchmaker and scientist Ferdinand Berthoud’s 18th century Marine Clock no. 6. Powering this watch is the manually wound calibre FB-RE.FC, which features a proprietary chain and fusée design and a remontoire device with a Reuleaux triangle.

The Reuleaux triangle

In 1981, Derek Pratt set to work on solving a problem that Breguet was not able to remedy – providing constant force to a tourbillon. As Andrew Crisford an expert on British watchmaking and Breguet, points out in his memorial in the British Horological Institute book, Breguet had attempted this in a couple of watches in which he had engraved “Echappement à force-constanté”, yet there is only one of these watches surviving, and it has since had its escapement replaced “due to the unsuitability of Breguet’s constant-force escapement for use in watches”.

Read DEREK PRATT: THE FORGOTTEN WATCHMAKER | A Collected Man Journal
Read DEREK PRATT: THE FORGOTTEN WATCHMAKER | A Collected Man Journal

Pratt’s solution was to incorporate a remontoire inside the tourbillon. This remontoire is what drives the tourbillon and is directly driven by the gear train. This means that the escape pinion that normally drives the tourbillon around the fixed fourth gear is replaced by the pinion attached to the remontoire. This one-second remontoire is attached to the escape wheel via the remontoire spring, which, as the name suggests, winds and releases every second, providing an impulse to the escape wheel.

The component of this construction that stands out more than most is the Reuleaux triangle. This curved equilateral triangle acts as a cam here, controlling the movement of the pallets that stop the remontoire wheel. Attributed to 19th-century German mechanical engineer Franz Reuleaux, the Reuleaux triangle is part of the Reuleaux polygons which all share the unique quality of having a constant diameter. This allows the tines of the fork in which it sits to remain in constant contact with the cam as it rotates and shifts the pallets with each rotation.