A lifetime automotive and aviation aficionado, MB&F founder Maximilian Büsser first channelled the visual cues of the mid 20th century in the 2014 HM6 Space Pirate, particularly in its “Streamliner” SV editions. Now in 2018, MB&F goes even further and presents one of its most ambitious designs yet – Horological Machine N°9 ‘Flow’. Its extreme curves and acute angles required new manufacturing standards and techniques to obtain a complete milled and finished case.
The new HM9 ‘Flow’ will debut in two titanium editions limited to 33 pieces each; the ‘Air’ edition comes with a dark movement and aviator-style dial while the ‘Road’ edition has a rose gold plated movement and a classic speedometer-style dial.
Reminiscent of a jet engine, the HM9 case is a geometrically complex combination of milled sapphire crystal and grade 5 titanium. Beating inside is an equally complex manual winding movement developed fully in house; the result of three years of development, with the accumulated experience that came with MB&F’s previous 14 calibres. Independent twin balance wheels beat at a leisurely 2.5Hz (18,000bph) on each flank of Horological Machine N°9, visible under elongated domes of sapphire crystal. The purpose of including two balance wheels is to obtain discrete sets of chronometric data that can be translated by a differential to produce one stable averaged reading. This purpose would be defeated by two balances oscillating perfectly in phase, giving the same chronometric data at every point.
A third pane of sapphire crystal reveals the central gearbox of the HM9 engine: a planetary differential that averages the output of both balance wheels to provide one stable reading of the time. Sitting perpendicular to the rest of the HM9 engine, the dial indicating hours and minutes is driven by conical gears that ensures precise engagement even when motion is put through a 90° planar translation. The winding and setting crown is located on the rear of the central body, its deep fluting providing ergonomic grip as well as aesthetic coherence with the overall design.
Two satin-finished air scoops are mounted alongside the pods containing the oscillating balance wheels, evoking the raised vents that allow continuous airflow to high-performance motor engines. HM9 Flow treads the path first opened by the HM4 Thunderbolt and subsequently by the HM6 Space Pirate, utilising a geometrically complex combination of milled sapphire crystal and grade 5 titanium case elements. However, HM9 goes beyond its predecessors, redefining what was thought to be possible in case design – illustrated for example by a patented three-dimensional gasket ensuring water resistance.
When the MB&F team first brought the HM9 designs to their manufacturing partners, the response was quick and unambiguous: these designs could not be realised. Other cases, such as the undulating shell of the HM6 Space Pirate, were geometrically complex, but their maximum height differential (the vertical distance between contiguous points) remained within 5mm. With HM9, that differential doubled, creating radical curves that give the case its highly tactile presence.
These steep curves are paired with slim bands of mirror polish and wider swaths of satin finish, raising issues when finishing tools of fixed diameter (say 10mm or more) had to somehow navigate the narrow channels of the case exterior. Adjusting the placement of different finishes in order to accommodate the finishing tools was not an option, as this would have diminished the full-volumed aesthetic of HM9.
The dramatic geometry of Horological Machine N°9 ‘Flow’ could only be supported by equally dramatic contrasts of finished surface, so manufacturing conventions evolved to meet the demands of HM9. Because of the proportions of the curves on the HM9 case, it was essential to control the overall size. Horological Machine N°9 ‘Flow’ measures 57mm at its widest point and requires a highly compact yet robust engine.