Horological Machine N°6 SV (SV for “Sapphire Vision”) adds an extra three-dimensional layer to the biomorphic beauty of the HM6 ‘Space Pirate’ by revealing the mechanical marvels of the unique Engine within. The complex curves of two transparent sapphire crystal plates sandwich a precious metal “streamliner” case band, creating two horological amphitheatres dedicated to the appreciation of exquisite, hand-finished micro engineering.
The case of HM6 SV is a sandwich construction of a precious metal case band between two transparent sapphire crystal plates. The case band, in either 950 platinum, forms a protective wall around the movement and supports the articulated lugs. Horizontal lines traversing the perimeter of the case band visually break the height of the case and accentuate the movement within. The sapphire crystal plates on the top and bottom were particularly difficult to machine and polish due to their size and the complexity of the curves. The domes capping the indications (top and bottom), turbines (top and bottom), and flying tourbillon were then meticulously fastened to the transparent plates thanks to a special gluing process, achieved under vacuum in a high temperature oven. This offers maximal strength and water resistance.
The production of HM6 SV’s 11 sapphire crystals, including two large case plates (top and bottom) and nine domes (on top and bottom of the two time indications and two turbines, plus one over the flying tourbillon) posed quite a challenge. Each was first machined from a solid block of sapphire crystal, which is the second hardest, naturally occurring mineral on earth after diamond. It is an incredibly demanding material to shape into complex forms. After machining each block of sapphire crystal inside and out with diamond tipped tools, the shapes have to be highly polished, both inside and out, to make them transparent. The domes are especially ambitious, as the walls have to be of absolutely uniform thickness; otherwise the slightest inconsistency creates disconcerting optical distortions.
The eye-catching central tourbillon perched high above the movement is a flying tourbillon developed by MB&F specifically for HM6. The choice of such a sophisticated regulator was necessitated by the restricted space under the top of the sapphire crystal dome, which could not accommodate the upper supporting bridge of a standard balance wheel. The flying tourbillon can be protected from ultraviolet radiation, which speeds up the oxidation of lubricating oils in the escapement and movement, by a retractable semispherical shield enveloping the tourbillon with four overlapping, curved blades. The shield is operated by a crown on the left side of the case. These blades are paper thin and had to be machined from a solid ingot of titanium.