Horological Machine N°9, also known as HM9 “Flow”, was first displayed in 2018 as a tribute to the great automobile and aircraft designs of the 1940s and 1950s. The outcome was a unique example that reflected the flowing, aerodynamic lines of the time.

MB&F creator Maximilian Büsser called the HM9’s engine “the most beautiful movement we’ve created to date,” despite its startling exterior. What other sensible course of action could be followed except to surround the HM9 engine in a clear sapphire crystal shell?

The HM9 ‘Sapphire Vision’ versions, also known as HM9-SV, were born as a result.

A curved, bubbled, and perfectly fitting three-part sapphire crystal and precious metal outer hull is sealed using a specialised blend of a patented three-dimensional gasket and a high-tech compound bonding method. Data is channelled into a differential by two completely separate cantilevered balances, which unify two heartbeats into a single coherent time pulse. The energy and information current from the engine are effectively turned via a 90° angle by ultra-precise conical gears to supply the time display on a sapphire crystal dial with Super-LumiNova markings.

Propellers are twin turbines that spin freely on the reverse, co-axial beneath each of the balances, ready for someone to start a different kind of exploration. Following the first HM9 Flow ‘Air’ and ‘Road’ editions’ conquest of the land and the sky, HM9-SV transports us to the ocean’s depths, the final place on Earth where a wealth of hidden mysteries still exist. An Atlantean exploration ship sits in front of you, propelled by a diverging technology that is both familiar and foreign to our eyes.

Externally, the HM9-SV’s lines float over the design of its predecessors with the designations Road and Air. Although the hydro-governed objectives allow HM9-SV to adopt a more forgiving attitude towards the acute inward angles and parabolic curves of the earlier Flow versions, the rules of fluid dynamics continue to dominate its design. Technically, the revised measurements were required to take into consideration the unique characteristics of sapphire crystal, which, although exceedingly hard, may shatter violently under pressure as opposed to a metal, which would just distort. The HM9-SV’s smoother contours minimise possible mechanical weak points while also enhancing the look of an ocean dweller.

The HM9 engine disregards movement building standards in order to continue the pathways set forth by the engines of Horological Machines N°4 and N°6. The dynamic outer casing of this three-dimensional assembly of wheels, gears, plates, and bridges, a beating union of mechanical viscera and endoskeleton in a crystalline body, takes on surprising shapes.

Although a 2.5 Hz (18,000 vph) conventional balancing frequency may seem rather antiquated in a modern timekeeper, using two balances rather than one accounts for the sensitivity to shock associated with a lower beat rate. According to statistics, two identically calibrated systems provide a better average reading than one system alone, which might produce abnormal readings due to a variety of factors.

The HM9-SV versions include a novel shock-absorbing technology that uses helicoidal springs between the movement and the casing to significantly lessen sensitivity to shocks. The springs have great elasticity and little lateral movement since they are laser cut from a solid tube of polished stainless steel.

A planetary differential, the movement’s gearbox, averages the time measurement from the two balances of the HM9 engine and then outputs a final reading to be displayed on the dial with a perpendicular orientation. The original HM9 Flow showed some of this complicated mechanical calculation by putting a sapphire crystal dome over each balance and a magnifying pane above the planetary differential. This was done to show how important the chronometric function of the watch was. Every feature of the HM9-SV engine may be explored, and the eye can follow how the many parts interact, from the barrel to the balance to the dial.

It was necessary to develop novel techniques to enclose the external sapphire crystal components in a single waterproof container. When the tripartite casing was put together in the first HM9 Flow, a patented three-dimensional rubber gasket was already utilised to assure water resistance. The 3-D gasket is still there in HM9-SV, but a high-tech bonding substance that was perfected through an internal procedure involving a vacuum and high temperature is what fuses the sapphire crystals with the iron frame. The end result is a seal that can withstand 3 ATM (30m) of water pressure, even though the sapphire components and the 18K gold frame’s simplistic design have virtually undetectable seams.

The HM9 Sapphire Vision was first offered in four versions, each of which had a maximum production run of five pieces. These editions included two with an 18K red gold frame and an engine that was NAC- or PVD-coated black or blue, as well as two with an 18K white gold frame and an engine that was PVD- or red gold-plated. Two new versions of the HM9 Sapphire Vision will be released in 2023: one with a PVD-coated blue engine and a white gold frame, and the other with a PVD-coated green engine and a yellow gold frame.

Both are part of a five-piece limited edition

One of the hardest minerals known to man is corundum, which is more widely known as sapphire crystal when it is in its gem-quality form. Only a few other substances are harder than corundum, including diamond (crystalline carbon), which is classified at 10 on the Moh’s scale, whereas corundum is classified at 9. Due to their exceptional hardness, sapphire watch crystals are virtually scratch-proof, offer the best long-term legibility and material integrity, and are more prestigious than the two most popular sapphire watch crystal alternatives (transparent polycarbonate and regular silicate glass).

This implies that milling sapphire into intricate three-dimensional patterns is very challenging, and the tight machining tolerances required in the watch industry make this difficulty even more challenging. Since the beginning of its innovations, MB&F has used ever-more-complex sapphire crystal components; HM2 “Sapphire Vision,” HM4 “Thunderbolt,” the most current HM3 FrogX, and HM6 “Alien Nation” are just a few notable examples.

It takes over 350 hours of meticulous machining and polishing to prepare the crystals for a single case of the HM9-SV—weeks of effort that would be substantially prolonged if not for the several years of ground-breaking sapphire crystal design that MB&F has collected since 2005.

The HM9 engine was created after three years of development, using only internal resources and the knowledge gained through MB&F’s 20 various movements to date.

The mechanical heritage of the HM9 engine will be familiar to long-time tribe members of the MB&F. Even though it has a very distinct visual shape, its double-balance system with differential is related to the same mechanism in Legacy Machine N°2. HM9 is jubilant in its appreciation of expressive design, in contrast to LM2, which focused on design purity and the hallucinogenic impact of its suspended oscillators.

When two balances beat at the same time, it is impossible not to talk about resonance, which is a mechanical phenomenon that describes coupled oscillators in a state of mutual harmonic excitation. Horological Machine N°9 purposefully avoids producing the resonance effect, similar to the LM2 engine. The purpose of using two balance wheels is to obtain distinct chronometric data sets that a differential can combine into a single stable averaged value. If two balances oscillated in perfect phase and provided identical chronometric data at every position, this goal would be defeated.

Controlling the dual balances presents a unique set of difficulties. An industry-standard device that regulates a watch balance assembly uses the sound that an oscillating balance makes to measure beat rate. This approach is not feasible here since the HM9 engine operates two balancing assemblies concurrently, producing two sets of noises. When Horological Machine N°9 was originally released in 2018, each example required blocking one balance in order to regulate the others, and vice versa. Before an ideal chronometric result could be obtained, several rounds of re-blocking and re-regulating were necessary since the calibration would vary somewhat when both balances were allowed to run.

The knowledge obtained in developing Legacy Machine Thunderdome has helped the MB&F team make considerable strides in chronometric control approaches since that time. Thus, HM9-SV gains from a few more years of specialised experience in this field. This advantage is negligible in terms of time but immense in terms of savoir-faire.

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