The Silicon-Powered Speed Of The Frederique Constant Slimline Monolithic Manufacture

One of the most noticeable trends in technical watchmaking since the end of the Second World War has been the evolution of watches with higher and higher frequency oscillators. A pendulum clock might have a pendulum that beats once per second. A watch has a balance, which can swing back and forth much more rapidly – a modern watch movement usually runs at 28,800 beats per hour, or eight beats per second. Some movements (the Zenith El Primero, for instance) can beat even faster, at 36,000 beats per hour. The new Slimline Monolithic Manufacture, from Frederique Constant, has a new type of oscillator, which runs at 40Hz – that’s a staggering 288,000 beats per hour. The watch was introduced in March, and even in the aftermath of Watches & Wonders, it’s still one of the most technically interesting watches of the year.
Any watch or clock is, at its most basic, an oscillator (the pendulum, a balance wheel) with a driving system (a mainspring in a watch, a falling weight in a pendulum clock) and a mechanism that both counts the oscillations, and drives the oscillator. This is the escapement.
Above, you can see the mainspring barrel on the left. The barrel rotates under the impetus of the mainspring inside it, and the teeth on the barrel gear to the pinion of the center wheel. The gear train ends, on the right, at the escape wheel and lever. (The balance wheel isn’t shown, for clarity.) As the balance swings back and forth, it unlocks the lever once per swing, letting the gear train advance. The gearing is set up so that the center wheel turns once per hour, and drives the hour and minute hands.
So why would you like to have an oscillator that beats faster than 36,000 vph? The answer is that such an oscillator should be more stable – that is, less apt to drift from its expected frequency. If a balance wheel were to always beat at exactly its expected frequency, you would have a perfect watch, but in reality, a number of factors can cause the frequency of a balance to vary, making the watch sometimes too slow, and sometimes too fast. Frequency varies when the oscillator is affected by outside forces, which can be aging lubricant in the watch itself, or changes in temperature, or the presence of magnetic fields, or physical shocks and changes in the position of the watch. The reason quartz watches are generally so much more accurate than mechanical watches is that a quartz oscillator beats at a much higher frequency – the tuning-fork-shaped quartz crystal hums at 32,768 beats per second.
The Monolithic Manufacture, on the other hand, uses a miniaturized version of the flexible one-piece oscillator design we first saw from Zenith, first in the Defy Lab, and then in the Defy Inventor. Rather than the usual combination of balance, balance spring, and lever, the monolithic oscillator in the Monolithic Manufacture uses a one-piece (hence, “monolithic”) silicon oscillator, which has integrated into it flexible central blades that allow it to oscillate, and an integrated lever. The oscillator has two weights mounted on it, which can be used to regulate the rate of the oscillator, just as rim weights on a balance can be used for the same purpose.

The connection between the Monolithic Manufacture and the Defy Inventor is of course, not a coincidence. Both were developed by a company called Flexous, under the direction of CEO Nima Tolou; Flexous was founded in 2012 and is a branch of surprisingly punctuated tech incubator YES!Delft.
The oscillator itself is a circular disk of silicon, and the blades, lever mechanism, and escape wheel are all silicon as well. Above, the escape wheel is at 12:00 (and is driven by the gear train, from the mainspring barrel) and on either side, you can see the teeth of the lever mechanism. The weights for adjusting rate are the two bars to the left and right, with grooves etched into the silicon to provide increments for the watchmaker. When running, the oscillator vibrates too fast for the naked eye to see individual vibrations, and the seconds hand advances 80 times per second, appearing to glide smoothly around the dial.
Conventional watchmaker’s electronic timing machines don’t work on an escapement that runs this fast, so the rate of the oscillator is adjusted with the help of a laser-controlled high-speed camera, capable of firing up to 250,000 times per second. While a standard balance in a mechanical watch usually swings through an arc of around 300º, the Monolithic Oscillator vibrates in a much smaller arc – just 6º, which is par for the course for very high-frequency oscillators.
Aside from the greater rate stability offered by a high-frequency oscillator, the Monolithic Oscillator offers the same general advantages as other silicon components – the most significant, of course, is that, unlike standard escapement components, it’s completely unaffected by magnetism. The Monolithic Oscillator seems to be a solution, too, to the most divisive quality of the Defy Lab’s oscillator, which is its sheer size. The size isn’t so much a problem if you’re looking for visual drama but it does limit the degree to which the technology can find its way into a larger range of watches. If the Defy Lab was a proof-of-concept, the Monolithic Oscillator is a demonstration that flexible silicon oscillators need not be a niche product – at least, there are no insurmountable technical barriers. The Monolithic Oscillator even manages to deliver a very respectable 80-hour power reserve.
The greatest difference between the Monolithic Oscillator and the Zenith Oscillator is size. The Zenith Oscillator took up the entire diameter of the case, more or less; the Monolithic Oscillator, on the other hand, was developed in order to make the basic flexible oscillator technology fit into the space normally occupied by the conventional escapement, balance, and balance spring. Doing so helps keep the watches at a friendly size for daily wear, as the Monolithic Oscillator uses much less space – the Monolithic Manufacture is a very wearable 40mm in diameter, vs. 44mm for the slightly larger Zenith.

Another advantage to the one-piece silicon oscillator is a reduction in parts count. The oscillator has just three components – the oscillator itself, and the two adjustable weights. These replace, in a conventional watch, the balance, balance staff, balance spring, collet (which attaches the inner coil of the balance spring to the balance), balance stud (the fixing point of the outer coil), the four jewels in the antishock system, two antishock springs, and the lever, lever pivot and lever jewels … as well as, come to think of it, the two jewels for the lever pivots as well. You also don’t have to worry about oil deteriorating on the balance pivots or on the escape wheel teeth, which is a ubiquitous cause of long-term rate variation in a standard Swiss lever watch.