The dream of a totally transparent watch
For the classical watchmakers, there was a parallel between the movement of the watch and the orbits of the planets and their moons, and so perhaps today some watchmakers still secretly dream of a movement in which the gears and hands are floating in space, silently revolving like a microcosm of the great timekeeper that is the solar system. This watch, the U20 Ultra-Skeleton Tourbillon by Angelus, reflects this desire for a totally transparent movement. But a watch remains a watch, with case, lugs and strap, and so any designer has to make compromises with the initial concept. In this case, transparency is maximized by a dome-shaped watchglass, a transparent caseback, and a sapphire dial that also acts as a mainplate. The bridges take the form of blued, chamfered titanium bridges, bolted to the sapphire.
U20, open architecture
The ultra-light case is made of carbon-fibre, titanium and sapphire; it is 42 mm in diameter and 10.3 mm thick, water resistance 30 metres. The lugs are in titanium, reinforced with a carbon fibre armature. Their technical shape echoes that of the titanium movement bridges. There is no bezel, and the dome-shaped watchglass rises directly from the case so that you can see the movement from the side as well as from above. The watch has an alligator strap with a titanium insert and a pin buckle engraved with the Angelus logo.
Angelus A-251 calibre
The Angelus A-251 calibre is hand-wound, with a mainspring barrel providing the exceptional power reserve of 90 hours. The balance is part of the flying tourbillon – flying because it has no upper bridge – and it has a variable inertia balance wheel, designed to reduce air resistance, with four gold weights for oscillation rate adjustment. It runs at 21,600 vibrations per hour, 3 Hertz. The 18 movement jewels are set in gold chatons, a nice classical touch within this high-tech calibre. The wheels have the characteristic Angelus 6-spoke design.
The sapphire used for the mainplate has to be specially machined from a solid block of sapphire, before being polished to perfect transparency. The process enables a micron-range tolerance to be achieved. The mainspring barrel bridge in titanium is supported by pillars set directly into the sapphire mainplate. Sapphire offers an advantage with respect to the conventional metals used for movement construction: it is naturally anti-magnetic.
Price and reference
The Angelus U20 Ultra-Skeleton Tourbillon is a limited edition of 18 pieces, reference 0TCAB.U01A.C004T. Each watch costs 66,200 Swiss francs.