Timekeepers Club / October 3, 2017

Ferdinand Berthoud - Chronomètre FB 1.3

Following the FB 1.1 chronometer in white gold and the FB 1.2 in rose gold, Ferdinand Berthoud presented the new Chronomètre FB 1.3, distinguished by a precious platinum case framing a partially openworked nickel silver dial.

The winner of the “Aiguille d’or” award at the 2016 Grand Prix d’Horlogerie de Genève, the Chronomètre FB 1 is endowed with a suspended tourbillon with fusee-and-chain transmission to ensure constant force for the escapement, two horological feats inspired by the 18th century Ferdinand Berthoud chronometers that served as reliable scientific instruments.

Produced in a 50-piece limited numbered series, the Chronomètre Ferdinand Berthoud FB 1.3 features a 44 mm-diameter case which is composed of a 950 platinum cylinder housing the movement and two side pieces in polished platinum that contribute to its distinctive octagonal shape.

The grey ceramic lugs are secured to the case middle by two stylised titanium bolts marking the starting points of the hand-stitched double-sided alligator leather strap.

The same ceramic is also present on the medallion adorning the knurled platinum crown. Finally, four ‘portholes’ cut out from the sides of the case provide a chance to admire the fusee-and-chain mechanism in action, as well as to allow light to flood through the movement.

Another opening in the satin-brushed nickel silver dial reveals the wheel driving the tourbillon carriage and the seconds wheel to which the central seconds hand is fitted, an unusual feature on a tourbillon. This slim black hand sweeps around a translucent sapphire railtrack circle around the rim of the dial.

The hours and minutes are offset at 12 o’clock on a black lacquered subdial bearing white Arabic numerals and white gold cut-out hands. The same black shade also graces the chamfered edges of the dial openings.

The nature and origin of the Chronomètre FB 1.3 are also indicated on this large dial that is engraved with the inscription “Chronomètre Val-de-Travers Suisse”.

The FB-T.FC hand-wound movement features 15 bridges and three half-bridges in non-treated German silver (a copper, zinc and nickel alloy that is particularly brilliant), framed by polished titanium pillars surrounding the mechanical organs.

This particular construction is typical of 18th century marine chronometers, and enables the portholes of the Chronomètre Ferdinand Berthoud FB 1.3 to reveal part of the mechanisms.

The fusee-and-chain transmission - the oldest historical solution developed to ensure constant force for the escapement - acts like an automatic gear box, with the torque delivered by the barrel varying according to the level of winding. When the movement is fully wound (53 hours of power reserve), the chain is entirely coiled around the small end of the fusee and the barrel spring is at maximum power. This force dwindles in the course of time, as the chain coils around the drum, moving from the small to the large end of the spindle-shaped fusee. The variation in the diameter of the fusee compensates for the reduction of the mainspring torque. The escapement thus receives constant energy, thereby equalling out the amplitude of the balance wheel and enhancing the movement’s timekeeping precision.

The distinctive nature of the FB-T.FC lies in the fact that its barrel and fusee are reversed, upside down, and above all suspended – meaning they are held on one side only. This solution helps saving a few precious millimetres and contributes to the overall slimness of the calibre. At just 7.96 mm thick, the movement powering the Chronomètre FB 1.3. is the thinnest in its category and a patent has been filed for this construction.

When the mainspring is associated with a fusee, the barrel drum turns in one direction while the spring is unwinding, and in the other during winding, thus serving to coil the chain. During the winding of this type of mechanism, the movement generally stops running. To counteract this effect, the FB-T.FC is equipped with a differential gear, enabling the balance-wheel to continue oscillating even during winding and thus preserving the movement’s precision timekeeping properties. Another patent has been filed for this device.

The winding mechanism fitted with a pinion featuring cone-shaped toothing, together with a large-diameter knurled crown, enables smooth winding of the movement, a key feature for a hand-wound watch.

As typically found on fusee-and-chain mechanisms, the barrel of Calibre FB-T.FC is equipped with a “Maltese Cross” stopwork device which serves to limit the number of winding turns of the mainspring to around six, and to use only the most stable portion of this spring. This device also servers as a buffer when the barrel is fully wound. At that point, the mainspring torque exerts a 3 kg force, which is considerable for components measuring just a few millimetres.

To perfect the security of the movement, the engineers at Chronométrie Ferdinand Berthoud have endowed the crown with a dynamometric function serving to avoid any damage to the movement that might be caused by excessive winding.

Teamed with the seconds wheel and pinion, the tourbillon of Calibre FB-T.FC comprises 67 components assembled within a titanium carriage measuring 16.55 mm in diameter, and fixed to an arrow-shaped steel arch whose tip points towards the space between the barrel and the fusee.

The assembling of the tourbillon cage and the spiral

The bridge assembled to the movement

This large-size tourbillon contributes to earning Calibre FB-T.FC its chronometer title awarded by the Swiss Official Chronometer Testing Institute (COSC). One particular characteristic makes this tourbillon different from others: in fact, although it performs one rotation per minute, it does not display the seconds. The Chronomètre FB 1.3 is one of the rare tourbillon models to have a central sweep-seconds hand.

All the movement components, including the 790-part chain measuring 285 mm, are meticulously finished by hand using traditional tools.

The Ferdinand Berthoud Chronomètre FB 1.3 has a price of Euro 257,000 / US$ 260,400.


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