In the world of watchmaking, the term “in-house movement” defines a calibre that is entirely designed and manufactured internally. Almost entirely that is, because in most cases the regulating organ is bought from a third party. The regulating organ (namely the balance wheel, hairspring and escapement) determines the precision of the watch. When you consider a true in-house movement to be a rarity, an in-house with in-house regulator is extremely rare. The small independent manufacture De Bethune is one of few manufactures that is truly independent, and able to create own in-house regulators to fit in their in-house calibres.
De Bethune sets itself apart from the crowd in more than one way, for instance with futuristic designs and use of novel materials. Cases of heat blued titanium are not unusual, at least not for De Bethune, and the same goes for their own regulating organ. While the balance wheel is usually crafted from an exotic alloy named Glucydur, De Bethune has created their own balance wheels with other materials to improve the performance.
The titanium and platinum balance wheel
Denis Flageollet, master-watchmaker and co-founder of De Bethune, is known to be a great inventor and pioneer. His work on the balance wheel was aimed to obtain the most stable, lightest balance wheel possible while maintaining the highest possible level of inertia.
For that, he created a titanium and platinum annular balance wheel, without the spokes of a classical balance wheel and shaped like a disc, with a blued central part made of titanium and external weights made from platinum. The titanium makes the central segment extremely light – 20% lighter than a normal one – while the platinum masses increase the inertia of the regulating organ. This lightness helps to reduce friction on the balance pivots and to also increase efficiency, boosting the power reserve.
The silicon and white gold balance wheel
In 2010 Denis Flageollet again improved his concept with a silicon and white gold annular balance wheel. This variation features a central part in silicon (a stable and antimagnetic material) with external weights made from a gold and palladium alloy. Again the stability is improved even more, with more lightness and an improved mass-inertia ratio.
The same technology is used for De Bethune’s hi-beat tourbillon regulator, in which the escapement vibrates with 36,000 vibrations per hour. Although here the combination of silicon and white gold-palladium alloy comes in a different shape, now with a central part is a wheel with spokes instead of the annular shape. This reduces the weight even more, and results in the lightest-ever tourbillon carriage, weighing only 0.18 grams. That’s four times less than a conventional carriage! This allows a greater durability and thus less wear on the movement.
An improved balance spring
De Bethune didn’t stop at balance wheels, it also conceived its own hairspring with a flat terminal curve. It’s an evolution of the Breguet overcoil balance spring, which is only used by the most prestigious watch brands. The small independent manufacture has improved this allowing a noticeably thinner construction and avoiding any distortion of the coils in case of impacts.
By Frank Geelen
Frank Geelen is an expert on Haute Horlogerie and beautiful hand-finished mechanical movements make his horological heart beats faster. He loves to explain all technical details of complications like tourbillons, minute repeaters, constant force escapements and column-wheel chronographs and he has been doing that for more than seven years. Besides publishing daily at Monochrome Watches (monochrome-watches.com) , Frank also writes for several other publications, both online and offline.