The Audemars Piguet Double Balance Wheel Openworked

The Royal Oak, thanks to the recent win by the Code 11.59 Universelle at the GPHG, is not necessarily the king of the hill at AP as a platform for complications but of course, it has over the years been used as a point of departure for just about every complication imaginable. Most of these are variations on classic complications – minute repeaters, for instance, or ultra thin perpetual calendars – but every once in a while something comes along that doesn’t fit neatly into any category. One such watch, launched in 2016, is the Royal Oak Double Balance Wheel Openworked.

The Double Balance Wheel Openworked is part of a larger general class of watches with two balances. Usually, these fall into two basic categories.

The first group are the very rare resonance watches, in which two balances are somehow coupled mechanically so that they influence each other’s beat rate and eventually begin to beat in synchrony with each other. As far as we know, the effect was first observed by Huygens, in two pendulum clocks, and Breguet famously experimented with resonance watches as well. He found it hard to believe that such systems could actually work but after testing several designs, he wrote, “This [resonance] appears to be absurd, but experiment proves it a thousand times over.” Today, F. P. Journe’s resonance watches follow closely in the footsteps of Breguet, although the are other solutions, including Armin Strom’s coupling spring resonance watches.

The second group are double (or multiple) balance watches, which two or more balances are linked with a differential. The classic example is Philippe Dufour’s Duality watch. The Duality, Dufour has told me, was intended to take the average rate of two balances, one of which was adjusted by him to run slightly fast, and the other to run slightly slow. As the watch assumed different positions with respect to gravity throughout the day, the positional errors should cancel out and at least theoretically you ought to get a better rate than you could from a single balance. Since the Simplicity came out, there have been a number of watchmakers and brands who have experimented with this solution – Greubel Forsey, for instance, has its Double Balancier watches which further refine the idea by setting the balances at opposing angles.

As far as I know, however, Audemars Piguet’s solution in the Royal Oak Double Balancier is unique. Instead of two or more independently oscillating balances, the Double Balancier has two but on the same balance staff, and therefore the same axis.

The superimposed balances each have their own balance springs, with opposed attachment points. The idea here is that first, the effects of gravity on the balances should tend to cancel each other out thanks to the arrangement of the balance springs, and the other is that two balances basically doubles the mass of the oscillator, which in itself should mean better resistance to the rate varying because of external disturbances.

There have been watches with double balance springs, some of them rather exotic – the H. Moser & Cie. Straumann double balance spring is one example. But the Double Balancier’s the only watch I can recall with two balances on the same axis, with two balances driven by a single escapement.

Although this solution has a number of theoretical technical advances, it does have one small downside: a lower power reserve, thanks to the extra inertia. Running at 21,600 vph, you get a reduction from about 60 hours’ power reserve to about 45 hours.

If you ask me, though, 15 hours of running time is a small price to pay for beauty. There is something about the combination of openworking and the double balance arrangement that I think suits the Royal Oak design to a T. The Royal Oak is a classic for a reason – the design was in its time a real revolution and it’s held up admirably over the subsequent decade. But for some reason, the ornately old-fashioned art of openworking a movement seems to work extremely well with that octagonal bezel around it. I think that traditional openworking by itself can seem fussy, and the Royal Oak, left to its own devices, can seem a little too overt-tough-guy for its own good. Together, though, they complement each other perfectly and with the double balance there to add a little unexpected magic to the mix, it’s a match made in heaven.

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