enis Asch trained as a watchmaker (and worked at Rolex for six years) before opening L’Heure Asch, a retail space in Geneva where he gave prominence to new names in haute horlogerie. Now a consultant and intermediary for collectors, Denis Asch is also an accomplished wildlife photographer which, as we shall see, is not entirely unrelated to the matter in hand.

Denis Asch: As someone who regularly exchanges with collectors and representatives of what we call haute horlogerie, sometimes I’m amazed by the “reverse snobbery” directed towards Rolex. There’s a tendency to look down on the brand and dismiss it as “industrial” but let’s not forget that Rolex is the result of all this…. [he points to the huge pile of technical documents relating to calibre 7135].

Denis Asch

Rolex is the sum of more than a hundred years of research and inventions, and I say this as someone who worked there, who went behind the scenes, who talked to the engineers, who saw how stringent the homologation criteria are. As far as I’m concerned, there is no match for Rolex in terms of reliability, robustness and precision over time. It wouldn’t occur to me to set off on a photo safari in Africa with anything other than my 1969 Rolex GMT. I challenge anyone to loan me a vintage watch that is anything like as resistant or that I can trust without a second thought.

I often compare watchmaking to photography. A wildlife photographer has to consider the often challenging conditions in which they work: the climate, changes in temperature, light and shadow, speed, the precise settings required for a good photo. There’s an entire process and watchmaking is no different.

What are the main challenges for a watchmaker?

Watchmaking’s greatest challenges, its “enemies”, are shocks, magnetism, gravity, friction, water-resistance and variations in temperature. Having read in detail the documentation supplied by Rolex, I’m impressed by everything they have done to combat all these enemies simultaneously. Ultimately, it’s the sum of details that determines the excellence of the whole. Chronometry and rate regularity are the result of these details. Put together, they all contribute but, more importantly, guarantee continuity and consistency over time. We’ve seen other inventive, innovative movements but this one, which meets all the challenges a watch encounters when worn, sets a very high bar.

Calibre 7135

We’re here to take a closer look at the innovations and choices, particularly regarding materials, that make calibre 7135 a next-generation movement.

First off, there is the Dynapulse escapement, as Rolex calls it, for which seven patent applications have been filed. It is designed specifically to optimise the distribution of energy from the mainspring to the oscillator and achieve the greatest possible efficiency by “losing” as little energy as possible. Rolex’s engineers worked on the escapement’s overall architecture, the materials used, the components’ geometry and surface quality. Also, the lighter the whole, the more efficient energy distribution will be.

What can we say about the overall architecture?

It’s a sequential distribution escapement in silicon. It’s remarkably light because silicon is half the weight of titanium and also because of the cutout geometry of the distribution wheels. These wheels have teeth and blades on the same level, the same plane. These blades mesh and the teeth alternately, sequentially, interact with the impulse rocker which gives impulse to the balance. This construction of the wheels reduces friction which in turn reduces energy consumption.

Dynapulse escapement

Frank Vernay, who is head of movements at Rolex, explained how the move from a 4Hz to a 5Hz frequency, a first for Rolex, results in more rapid consumption of the power supplied by the automatic winding system, and that this had to be optimised in order to maintain a power reserve of around 66 hours, comparable to that of the earlier calibre 7140. But why increase frequency to 5Hz or 36,000 vibrations per hour, which can measure tenths of a second, when this isn’t a chrono?

Beyond the fact this frequency, which can effectively measure tenths of a second, gives the seconds hand a smoother gliding motion, the higher the frequency, the more stable the rate. The movement is even more robust, more shock-resistant. Also, a balance wheel that makes ten vibrations per second, which is the case at 5Hz, can be adjusted with greater precision than at 4Hz or eight vibrations per second. Back when Rolex was still equipping its Daytona with El Primero movements beating at 36,000 vibrations per hour, it used to slow them down to 28,800 vibrations per hour because they were far too energy-hungry. Maintaining 66 hours of power reserve therefore implies a number of technical choices.

Which presumably influence manufacturing processes and require changes on an industrial scale?

This is what Frank Vernay means when he says assembly of the Dynapulse escapement in the calibre, including the lubrication process, which uses oil rather than grease, required a complete rethink of the movement manufacturing and assembly process that obliged Rolex to take a completely novel approach.

Ceramic balance staff

The oscillator itself has been the subject of considerable attention, starting with the balance staff.

That’s right. It’s made from ceramic, white ceramic as it happens, which Rolex tells us is polished “to nanometric scale”. A nanometre is one billionth of a metre. That’s 0.000000001 or 10-9 metre. At watchmaking school, our teacher used to judge how well we had polished our balance staffs by looking at them under a microscope and nothing got past him, not the tiniest imperfection. Every micron of polished surface represents an infinitely small energy gain. As well as being antimagnetic and extremely strong, which prevents microfissures forming in the event of an impact, ceramic allows for optimal geometry and a perfectly smooth surface state, polished by a femtosecond laser. Yes, we’re talking industrial, but this is industrial at its very best.

Balance and Syloxi balance spring

We could examine every detail in turn and come to the same conclusion…

A movement is a whole which, in order to optimally function, must be coherent. It’s a chain. A train whose carriages are all connected. For example, the balance wheel is in “optimised brass”, an alloy Rolex is using for the first time because its magnetic resistance is comparable to that of the ceramic for the staff. It comes back to coherence. Similarly, friction has to be reduced across the entire chain. The geometry of a part, its surface state, lubrication, strength… everything is important.

Lying in wait for the perfect shot

The balance wheel, which is cushioned by two “optimised Paraflex” shock absorbers, is fitted with a Syloxi balance spring which apparently you find particularly impressive.

That’s right. The Syloxi balance spring in calibre 7135 is a silicon and silicon oxide composite, hence insensitive or less sensitive to temperature variations, magnetic fields and shocks. Also, Rolex has developed a special patented geometry for this balance spring in which the coils become thicker and further apart along its length [thanks to the high-precision Deep Reactive Ion Etching manufacturing process]. This innovation ensures regular oscillations in all positions as well as more precise adjustment which compensates for the effects of gravity in vertical positions, where it is strongest. This nanometric detail demonstrates the considerable research and development that went into this next-generation calibre.

According to Rolex, it was ten years in development.

I’m not in the least surprised. This isn’t just about conceptualising and manufacturing a new movement. There had to be a complete rethinking of the entire chain. New manufacturing and industrialisation processes had to be developed, including for casing. Even the certification process had to be revised. Rolex has to guarantee the movement’s reliability and, because it runs at 5Hz rather than 4Hz, adapt measurement and certification methods, hence develop new algorithms. Calibre 7135 is certified to Rolex’s Superlative Chronometer standard. Once the uncased movement has passed the usual COSC [Contrôle Officiel Suisse des Chronomètres] tests, because casing can cause slight deregulations, Rolex then performs a second series of tests on the cased movement. It also carries out additional testing on the finished watch, such as for water-resistance and power reserve, in conditions that simulate real-life wear. Whereas COSC certification requires an average daily rate of -4/+6 seconds, for Rolex Superlative Chronometer certification this variation cannot exceed -2/+2 seconds per day.

In photography, the perfect harmony between shutter speed, aperture and ISO determine whether a photograph is a success or not. In mechanical watchmaking, performance hinges on the flow of power and the precise coordination of distribution and regulation. In both, every factor must be carefully weighed in the pursuit of excellence.