Ferdinand Berthoud, Chronometry and the FB1-R Regulator

Resurrecting the Ferdinand Berthoud name, an eminent 18th-century horologist, Karl-Friedrich Scheufele (co-president of Chopard) and his team have shown quite a talent to surprise and amaze us. The niche, high-end brand has presented several creations that are not just nostalgic products but modern wristwatches. These are nonetheless loyal to the legacy of the name Berthoud. In particular, the brand’s first modern opus, the Chronomètre FB1 was awarded the Aiguille d’Or at the GPHG 2016, the Oscars of watchmaking. 

Ferdinand Berthoud was born in 1727 near Neuchatel, Switzerland but moved to Paris to practise his trade. He left behind an exceptional legacy and a broad body of work, in particular in the field of marine chronometers as watchmaker-mechanic to the French King and the Navy (Horloger Mécanicien du Roi et de la Marine).

Reviving his name, chronometry has come to occupy a very special place. Based on the same calibre architecture, all modern Ferdinand Berthoud watches incorporate several mechanisms to optimize precision. To date, these are all regulated by a tourbillon that is driven by a constant force mechanism, a fusée-and-chain. This was the case for the FB1, the FB1-R or the FB1-L.

The period of oscillation of a watch balance wheel is affected by the variation of the driving force delivered by the barrel. This led watchmakers to design mechanisms to compensate for the variations in torque of the mainspring. A fusée consists of a cone-shaped pulley, linked to a chain coiled around the barrel. The fusée features a spiral thread to receive the chain. Thanks to the increasing circumference of the thread, the diminishing force of the mainspring is compensated (very much like the gearing of a bicycle). As the mainspring unwinds, the chain rolls on the barrel and off the fusée. The increasing leverage of the fusée compensates for the waning torque of the barrel.

The fusée-and-chain features a Maltese cross stop-work. Fitted on the drum of the barrel, it limits its turn, creating a locking point to prevent any damage from overwinding. It also enhances a consistent delivery of power, using the mainspring optimum range only and avoiding the low and high torque extremes.

All Ferdinand Berthoud watches are chronometers and are certified by the COSC (the Official Swiss Official Chronometer Testing Institute) after completing 15 days of testing. If this is the least you would expect from a watch fitted with a tourbillon regulator, not so many brands are actually going through COSC certification. What is even more impressive, Ferdinand Berthoud recently communicated the results of the 15 calibres of its regulator-type Chronomètre FB 1R that have been submitted to the COSC. These are expressed with two variables:

• 1.66 seconds of daily variation in rate, in six different positions. This is the average deviation displayed by the model in daily wear. The COSC requirements are between -4 sec to +6 sec per day.
• 0.35 seconds/day in restart mode. This variable measures the precision of the watch throughout its power reserve. In other words, it must be as accurate when it is 100% wound as at the end of its power reserve or when resuming operation. This illustrates the efficiency of constant force mechanisms.

Besides the technical demands, the brand dedicates lavish attention to the manufacturing and finishing of its watches and movements. The pillar-type architecture of the movement is another nod to yesteryear marine chronometers. Based on traditional techniques and extensive hand-work, the decoration is impressive. To ensure a flawless finish, the brand’s craftsmen check their work under an x10 magnifying glass!

Ferdinand Berthoud has just released a series of videos to present the core expertise of the brand. In addition to the first one on the fusée-and-chain mechanism, the following one shows the way watchmakers at Berthoud decorate a movement, the traditional way.

More details at www.ferdinandberthoud.ch and at the brand’s YouTube channel, for more beautiful videos.