Bernhard Lederer wrist presents the final two expressions of the new face of chronometry. Lederer Watches presents the Central Impulse Chronometer in a steel version and in a rose gold version. On the occasion of Geneva Watch Days 2023, Bernhard Lederer is delighted to present the final two series – Series 3 & Series 4, which bring to a close the amazing adventure of his celebrated Central Impulse Chronometer.
In all, only 100 pieces will have been offered to collectors, Series 1 : 25 pieces in white gold, Light Rhodium dial, presented in 2021, Series 2 : 25 pieces in white gold, Deep Blue dial, presented in 2021, Series 3 : 25 pieces in rose gold, Black Rhodium dial, presented in August 2023 & Series 4 : 25 pieces in 904L steel, Pacific Green dial, presented in August 2023.
The latter two series, designed for discerning and refined collectors, will be highly coveted, firstly for the metal they are made of: 25 pieces in 18K rose gold, more precious and more elegant, and 25 pieces in 904L steel, a super alloy that is even more complex to machine and exceptionally durable.
As a showcase for remarkable horological engineering and ingeniousness, they also represent the ultimate opportunity to acquire a watch that has thrilled experts the world over and is considered one of the most ambitious and demanding chronometric projects – the development of the escapement – of recent decades.
During the prototyping phase, Bernhard Lederer noticed a marginal but nonetheless disturbing fact: Despite the presence of constant-force remontoire in each of the two independent gear trains, the watchmaker noted a slight increase in the oscillation amplitude of the balance towards the end of the movement, inducing a tiny rate deviation in the running rate.
Why was the amplitude increasing at the end of the power reserve? Because, when the torque delivered by the barrel spring weakens, the pressure of the remontoir wheel teeth on the pallets of the remontoir anchor is reduced. De facto, the resistance to winding decreases, so more force is transmitted to the escapement wheel. Ergo, amplitude increases.
To remedy this, Bernhard Lederer re-imagined the remontoire. Traditionally, it is equipped with a saw-toothed wheel. This is what traditional watchmaking treatises had always advocated, so that was the concept Bernhard Lederer spontaneously opted for. But in practice, the watchmaker realized that it was precisely this ‘contact’ between winding wheel and anchor that needed to be modified if the amplitude error associated with the power reserve coming to an end was ever to be totally rectified.
Now, a straight-toothed wheel drives a pinion with a two-armed wing, which is released every 10 seconds by the winding fork for half a rotation.
The result, in terms of chronometric efficiency, was immediate: The triggering resistance was reduced by a factor of 10, as was the ratio between wheel and pinion, which considerably increased the efficiency of the remontoire. Importantly, it rendered the difference in triggering resistance negligible. Today, it is no longer possible to detect or even measure a variation in amplitude, as the Central Impulse Chronometer maintains a constant amplitude throughout the entire movement. Its regularity is quasi-perfect.
Drawing on almost 40 years of experience and supported by his team in Saint-Blaise near Neuchâtel, Bernhard Lederer took up the torch that George Daniels had lighted with his Independent Double-Wheel Escapement. Daniels himself had taken Breguet’s work a step further by solving the issues this type of escapement was known to have. That is why the Central Impulse Chronometer escapement has a very different design.
It incorporates two independent escapement wheels, each linked to its own barrel. These wheels work in alternation with a unique anchor. Its profile, its rubies, its lifting angles, its central impulse and the way it comes into contact with all the components it guides make this an extraordinary system.
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