An octagonal case, a tourbillon motion with fusee-and-chain transmission and a pillar-based development: the Chronomètre FB 1 has performed a significant position in defining the id of Chronométrie Ferdinand Berthoud. Calibre FB-T.FC powering this mannequin is now making ready to take a final bow, within the type of a closing 38-piece version introduced for the primary time with a spherical case: the Chronomètre FB 2T.
Geared up with a constant-force system often called fusee-and-chain transmission, Calibre FB-T.FC encompasses a distinctive modus operandi, as winding will not be achieved through the barrel, however by way of a differential positioned within the centre of the fusee. This mechanism serves to cut back the drive required for winding. Seventy turns of the crown are thus required to totally arm the mainspring, easily and with out the slightest effort. Its 9 mm diameter makes the crown straightforward to grip. Additionally it is geared up with a security system to guard the motion from extreme winding.
Situated on the high of the barrel, a Maltese Cross stopwork system mechanically limits the working vary of the mainspring the place its torque is most fixed. Though the barrel can doubtlessly carry out eight full revolutions itself, the Maltese Cross permits solely six, marked by the six tooth on its profile. The final two indentations on the Maltese Cross stop the mainspring from delivering an excessive amount of vitality to the gear prepare (simply after full winding) or too little (on the finish of the ability reserve).
Throughout all the 53-hour energy reserve, this fixed vitality is delivered to the escapement, a tourbillon with central seconds, for which a patent has been filed. Positioned at 6 o’clock, the tourbillon carriage engages straight with the seconds (fourth) wheel because of a wheel situated on its axis whose diameter and properties are equivalent to these of the seconds. The 2 wheels thus make a whole rotation in 60 seconds: the seconds (fourth) wheel in a clockwise path and the tourbillon wheel counter-clockwise.
This specific development optimises the move of vitality transmission by protecting the required variety of gears to a minimal and likewise lowering the danger of irregularities on account of friction. A protracted central wire-shaped hand thus shows the seconds precisely and with none stuttering of the hand—very very like the Marine Clocks produced by the Grasp Watchmaker who devoted his life to the hunt for precision.
The facility-reserve show of calibre FB-T.FC is predicated on a patented course of that’s as considered as it’s elegant. Straight linked to the barrel by a large-diameter driving wheel, the mechanism makes use of the motion of arming and disarming the mainspring to maneuver a cone up and down a threaded central arbor connected to the mainplate.
A feeler tipped with a ruby curler finish measures the upward and downward motion of the cone. When the motion is totally armed, the cone is on the high of the threaded arbor and the feeler arm due to this fact rests on the base of the cone (its widest diameter). Because the motion is disarmed, the cone rotates and strikes down the threaded arbor.
The diameter of the cone on the feeler decreases and the feeler strikes nearer to the axis of the threaded arbor. The feeler arm rotates by about 15°, as does the rack beneath it, which is on the identical axis. It’s the latter that transmits the motion’s power-reserve stage to the hand on the dial facet.
Three variations can be provided by the Maison: FB 2T.2 in 18-carat rose gold with a black satin-brushed dial; FB 2T.2-1 in 18-carat rose gold with a ruthenium satin-brushed dial; and FB 2T.1 in 18-carat white gold with a blue satin-brushed dial.
These three references are sources of inspiration for collectors who could have the chance, for this “Closing Version”, to create their very own customised timepiece by selecting the case materials, the color and the ending of the dial and the leather-based strap. There may be nonetheless a restrict with regard to the case form: this FB 2T assortment is obtainable solely with the spherical case introduced in 2020 with the FB 2RE Remontoir d’Egalité assortment.