Watchmaking artistry
How the atelier skeletonises a Valjoux 7753, and why the dial is openworked.
On its skeletonised chronographs, B.R.M starts with a Valjoux 7753 automatic calibre and skeletonises it by hand in the Magny-en-Vexin atelier: material is removed until only what works remains. The movement is then suspended in the case on shock absorbers, and the dial is open-worked so that one can see it functioning.
The Valjoux 7753 is an automatic chronograph. On B.R.M specification sheets, it is described as follows: 27 jewels, 28,800 vibrations per hour, 46 hours power reserve, 7.90 mm thickness, hacking seconds. It counts the chronograph seconds over 60 seconds, with two counters for 30 minutes and 12 hours; the pusher at 2 o'clock starts and stops the chronograph, the one at 4 o'clock resets it to zero.
Each skeleton movement is conceived and skeletonised by hand by the atelier teams. Material is removed until only what functions remains. On the specification sheets, these calibres bear the mention "Calibre Valjoux 7753 skeletonised by BRM".
The skeletonising is carried out in the same place as the case machining and assembly: in Magny-en-Vexin, under the same roof.
At B.R.M, the movement ring is mounted on shock absorbers and the movement is suspended within the case. This is why the dial is openworked: the maison considers there is nothing to hide.
The MK-44 is the house's skeleton chronograph on a Valjoux 7753 skeletonised by BRM. Its 44 mm case is in Makrolon®, a transparent material that reveals the heart of the watch; lugs, crown and crown guard are in machined and lightened titanium, the screws in grade 1 titanium. The watch weighs 47 g. Sapphire crystal above and below, screwed crown, water resistance 100 metres.
The hands are perforated, with a tip coated in Superluminova® for reading in darkness; their colour follows that of the version. The strap closes with a lightened titanium pin buckle.
The MK-44 is available in several colours and in polished Makrolon finish, from 10,430 €.
The MK-44 appeared in 2012: Makrolon® case, Fortal® HR case back, under 50 grammes. The Makrolon® is transparent: it reveals the skeletonised calibre through the sides of the case as well as through the dial.
The movement ring of the MK-44 is mounted on shock absorbers and its balance wheel is shock-protected, as on all the house's watches, where the calibre is never screwed directly to the middle case.
The V12-44 Damier Squelette combines a skeleton dial, a Valjoux 7753 calibre and a 44 mm case in black PVD-treated titanium with a chequerboard pattern. It is offered at 16,270 €.
The workshop also skeletonises three-hand calibres: the ETA 2824-2 on the V6-44-SA skeleton or the GF6 skeleton, the ETA 2671 on the GF7 skeleton.
View the MK-44, the V6-SA et the workshop.
A Valjoux 7753 automatic calibre, hand-skeletonised at the Magny-en-Vexin workshop.
46 hours, according to B.R.M specifications.
47 g, with a 44 mm Makrolon® case and titanium lugs.
By hand, at the manufacture's workshop, in Magny-en-Vexin.
