Christophe Claret puts "impossible" escapement in the Maestoso
Some upmarket wristwatches are all bells and whistles, while for others their attraction isn’t in what they do, but how they’re made. One case in point is the Christophe Claret Maestoso showcased at Baselworld 2014, which uses a detent escapement – a movement of remarkable accuracy that’s almost impossible to install in a watch.
Designed and built by Manufacture Claret, the Maestoso takes design cues from the times of Louis XIV and Charles X of France. It features a hand-wound, 44-jewel DTC07 movement with 301 components. Claret is clearly proud of its working, given that it has made as much of the movement as possible visible on both the obverse and reverse using Charles X-style skeletonized stepped bridges. But the real hook of the Maestoso is its detent escapement in grade 5 titanium.
Put simply, the detent escapement is a catch that turns the unwinding of a spring into a time-keeping mechanism. It works by means of a toothed escape wheel that’s held static by the detent until a spinning roller with a single tooth powered by a spring and balance wheel strikes the escape wheel, releasing the detent and causing the escape wheel to shift forward before locking again.
The detent escapement was invented in 1748 and is much more consistent than the levers used in conventional watch escapements, with accuracy approaching that of a quartz watch. It has the added advantages of not needing to be oiled, which adds to its accuracy because there’s no danger of friction building up or the lubricant getting dirty or turning gummy.
It was used from the middle of the 18th century up until the development of electronic clocks for maritime navigation in the 1970s. Unfortunately, though the detent escapement is extremely accurate, it isn't self-starting and is also very vulnerable to lateral shocks, with a bump potentially causing it to stop or let slip its escape wheel. It also has the problem of over-banking. That is, the balance wheel could swing more than 360 degrees, which causes a second impulse that throws the timing off.
All of this meant that for for two hundred years the natural habitat of the detent escapement was in clocks mounted on gimbals aboard ships to protect them from shocks.
Watches are very hostile to detent escapements, and though the detent escapement was used in pocket chronometers to synchronize the time between observatories and town clocks, they weren’t very successful in domestic timepieces, such as wristwatches, and building a wristwatch with a detent escapement is still a major challenge. Claret’s way of approaching the problem was to develop a new system that’s won three patents.
The Maestoso solution for protecting the detent escapement is by preventing it from turning over. It does this through an anti-pivot cam in the spring balance that works in conjunction with a safety finger. The mechanism is fitted between a mainplate and two sapphire bridges, and pivots on a ball bearing. This distributes the load on the escapement, reducing the chances of it slipping or stopping.
Claret has also provided the escapement with a flexible thrust bearing that absorbs excess energy to prevent over-banking. Meanwhile, a constant force spring feeds power from the mainspring without variation, making the torque to the escapement more constant. Another patented innovation is a stop seconds, which stops the balance when the time is being set to avoid any chance of damage.
There’s also a micrometric worm screw on the regulator to regulate the timing rate, and two mainspring barrels with two superimposed springs, each with a power reserve of 80 hours. Sapphire bridges allow you to see into the movement and observe the escapement in action.
The Maestoso is set in a case tested to three atmospheres and is available in 5N red gold, anthracite PVD titanium with white gold, or anthracite PVD titanium with red gold. The hour and minute hands are made from titanium and rubies with a luminescent coating, and the watch is secured with a black alligator leather strap with black stitching and stainless steel strap with anthracite PVD-treated titanium caps. The flange is of black rhodium-plated nickel silver with a white lacquer Christophe Claret logo and indexes in rhodium-plated brass and lacquer.
The Maestoso is available in a limited run of 20-pieces for each variant with a price range of US$178,000 to $186,000.
Source: Christophe Claret