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Bernhard Lederer introduces a new Central Impulse Chronometer using a natural escapement with two 10-second constant-force mechanisms in a sleek watch with a movement of exceptional complexity.
Press Release with commentary in italics:
Bernhard Lederer – a legacy of high complications
If you have never heard of Bernhard Lederer, you are either too young, or not steeped deep enough in the world of independent watchmakers, or both. Bernhard is a Académie Horlogère des Créateurs Indépendants (AHCI) member since its inception in 1985, and have been practicing the art of high horology for the last 40 years in his atelier in St Blaise near Neuchâtel.
Through his brand Blu, Bernhard is the inceptor of numerous breakthroughs in watchmaking and creator of extraordinary tourbillons. He returns to center stage with a new collection entitled ‘Tribute to the Masters of Escapements,’ a limited series of precision chronometers designed and developed to honor those who set true milestones in the advancement of an horological invention that remains as crucial and fascinating as ever. This latest release is the Central Impulse Chronometer. With this piece, Bernhard completes the work on the natural escapement initiated by George Daniels, who himself had taken over where Breguet left off.
Central Impulse Chronometer
The Central Impulse Chronometer escapement is the ultimate, reliable and stable embodiment of the mechanical movement’s counting and regulating system designed by George Daniels. It is composed of two escapement wheels operating in alternation and connected to an anchor that is absolutely one of a kind. Its profile, rubies, angles of lift, even the way it comes into contact with all the components it guides, make this an exceptional creation. Not least because the contacts are so light and gentle that the escapement is remarkably quiet, whilst emitting a unique sound every 5 seconds each time one of the two alternating constant force remontoires springs into action.
Yet all this sophistication remains elegantly subtle. The Central Impulse Chronometer comes in the form of a watch in a sleek, understated round case in rose gold with a smooth bezel. The dial is vast, minimalist in its markings, save for a small seconds at 8 o’clock with a circular finish. The sleek, 44-mm round pink gold case is elegantly understated. Its fine, smooth bezel emphasizes the vastness of the light grey, opalescent dial with a signature at 3 o’clock and raised beveled indices featuring a touch of SuperLumiNova™. The shape of the rose gold beveled hands, a hybrid of leaf and baton, underscores the Bernhard Lederer aesthetic signature. Challenging the symmetry, a large-diameter, circular-finished small seconds subdial at 8 o’clock.
The Central Impulse Chronometer is also available in a white gold with an openworked slate grey sunburst dial. The generous window provides an unobstructed view of the Caliber 9012 and its most distinctive features,
namely the remontoires and escapement. It is the ‘technical’ counterpart to the ‘minimalist’ rose gold version, whose complexity remains hidden from view until the watch is turned over. Here, a sapphire crystal case back
reveals the architecture of the Caliber 9012, which is symmetrical, angled, widely openworked and quite large at 39.3 mm in diameter.
The Bernhard Lederer Central Impulse Chronometer Version 2 in WG and an openworked dial.
The movement – Caliber 9012
To achieve the precision of his Caliber 9012, Bernhard Lederer installed these two escapement wheels at the end of two separate gear trains, each with its own barrel and its own 10-second constant force remontoire. In finely evening out the driving force, optimizing the geometry of the escapement parts, paring down the weight of these energy-intensive components, and reducing the internal friction of the escapement to a minimum.
The movement is a completely new designed caliber from ground up by Bernhard. The movement is laid out symmetrically, with two trains as two wings of the movement feeding the balance wheel in the center.
The two trains, laid out symmetrically. Note the complex transmission wheel to drive the winding of the barrels.
A frequency of 3 Hz was chosen because a watch worn on the wrist is subjected to countless shocks of varying intensity. Each one has repercussions on the movement’s regulating organs, i.e. the escapement wheels, but more importantly on the balance wheel with its spiral spring. With each impact, there is an acceleration or a slow-down, and the components find themselves twisted in their plane. They must therefore resume their intended course as quickly as possible, which is a sine qua non for precision under everyday wear conditions. In addition, the escapement is a system that spends most of its time at a standstill. Whilst the balance wheel is in perpetual rotation, it only activates the anchor at the end of each oscillation: when it has the highest velocity, i.e. the greatest force, and thus the best capacity to drive the mechanism. The anchor and anchor wheels are in a constant stop and go, accelerated and decelerated, which consumes energy and impairs isochronism and therefore precision.
To overcome these problems intrinsic to any escapement, the Central Impulse Chronometer uses components made from titanium instead of the more traditional steel. Lighter, stiffer and with a lower inertia, they are quick to restart and much more energy-efficient. In other words, the balance wheel’s rhythm remains virtually unaffected by the contact with the anchor.
It receives the force necessary for each impulse, itself an assurance of isochronism and therefore of timekeeping precision. The quantity of energy delivered is also controlled further upstream, in the gear train. Bernhard Lederer installed two independent gear trains, one for each escape wheel. Each of these kinetic chains has its own dedicated barrel. What is more, Bernhard Lederer inserted a constant force remontoire.
The constant force remontoire consists in accumulating an energy buffer in a spring similar to the one in the barrel, but one that is much shorter and lighter. Recharged in 10-second intervals, it capitalizes on the fact that the force of an unwinding spring is stronger when it is tightly wound up, and weaker when it is almost completely unwound. This variation in torque has a direct impact on isochronism. The remontoire equalizes the force by ensuring a very homogeneous torque profile, with extremely minute variations in the energy delivered to the balance wheel. Here, Bernhard chose a design similar to the one invented in 1756 by John Harrison, where the remontoire recharging interval is managed by an anchor with a specific profile.
The left wheel train’s escapement wheel, showing the remontoire coiled inside, and the engagement point to the direct impulse system.
At a more fundamental level, the mechanical specificity of the Central Impulse Chronometer escapement lies in its anchor. It is the interface between the two escapement wheels, i.e. the gear train and the balance wheel. As the metronome, as it were, of the timepiece, it is where the energy of the former is transformed into the time information delivered by the latter. To improve performance, the Central Impulse Chronometer’s anchor presents more points of contact between the components – whose shape, too, has been optimized. In particular, Bernhard Lederer has added a minutely small ruby, with a concave cut in the center, which advances the moment of contact between the escapement wheel tooth and the balance wheel impulse pallet.
The natural escapement in the Laurent Ferrier Galet Micro-rotor Echappement Natural. In the Lederer implementation, the escape wheel is armed with its own 10s constant force remontoire, while the Ferrier had no constant force system. This animation video serves to show how the direct impulse natural escapement works.
Indeed, this is the most remarkable feature of the Central Impulse Chronometer: the manner in which it manages the moment and the contact surface of the impulse on the balance wheel. The impulse is direct and in alignment from the escapement wheel to the balance wheel, therefore theoretically perfect. In addition, control of the impulse position is constant over time, both at low and high amplitude of the balance wheel. In fact, due to the geometry of the receiving pallet, the anchor will be able to give an indirect impulse to the balance wheel, allowing it to be always in the desired position when the direct impulse is given. As a result of the force being transmitted in this position, shocks are attenuated and the balance wheel receives the impulse in such a way as to ensure optimum isochronism and stability.
The planetary click system in the transmission wheel to transfer the winding from the crown to power up the mainspring barrel.
The concrete effect of this ingenious arrangement: fewer shocks between the components, smoother transfers of energy. The driving force is effectively dampened, though not in its intensity, but instead at the point of contact. It is when the escapement wheels and the balance wheel connect that the heartbeat of the watch, the ticking sound, is generated. These ever so slight impacts have been further mitigated to a degree that the Caliber 9012 is surprisingly quiet. George Daniels, an expert in vintage automobiles and an admitted petrol head, would have appreciated how the movement purrs like a well-tuned engine. This ‘engine’ is so well tuned that one hardly
The two movement comprise of two separate trains driving a single large balance wheel through the direct impulse escapement – known as echappment natural in French, or natural escapement. Most other implementations of the natural escapement end here. But Bernhard adds two remontoirs to provide a constant force to the escape wheel (the remontoir spring lies between the fourth and fifth wheel, and isolates the fifth wheel from the mainspring. This adds a significant level of complexity to the movement.
From the high resolution photographs we received, the complexity of the movement is spectacular, and coupled with the beautiful symmetry of the architecture is a feast for the eyes. The movement finishing looks top grade, as we would expect from an old master like Bernhard Lederer.
The Central Impulse Chronometer, the first chapter of the ‘Tribute to the Masters Of Escapements’ collection, is a complete watchmaker’s work, where mechanical achievement finds itself amplified by the sophistication that went into the finishing. In this regard, Bernhard Lederer follows through in the footsteps of Breguet and George Daniels, and lays his own. Engineering prowess remains the foundational core of the Central Impulse
Chronometer. The result of several years of intense reflection and work, the Central Impulse Chronometer is a testament to Bernhard Lederer’s sincere admiration for George Daniels, reflected in a scrupulous respect for the master watchmaker’s approach. To have succeeded in bringing this chronometer into being is the pride of a humble human, a conscientious watchmaker and a discreet designer.
We look forward to handling the actual watch, and the next chapters in the “Tribute to the Masters of Escapements” collection in person and take our own photographs to report back to you for a hands-on detailed review.
Bernhard Lederer Central Impulse Chronometer Specifications
Name: BERNHARD LEDERER CENTRAL IMPULSE CHRONOMETER
Functions: Hours, minutes, small seconds at 8 o’clock
Case: Version 1: rose gold 5N 18K Version 2: white gold 18K
Diameter: 44 mm
Thickness: 12.2 mm
Case back: Open, sapphire glass with double anti-reflective coating
Water resistance: 3 ATM, approx. 30 metres
Dial: Version 1: solid dial, silvered opaline Version 2: openworked, slate grey sunburst
Movement: Mechanical, hand-wound
Number of components: 208
Number of jewels: 44 rubies
Frequency: 21’600 vibrations per hour (3 Hz)
Diameter: 39.3 mm
Thickness: 5.98 mm
Special features: Double barrels, Two independent gear trains, Two constant-force remontoires, Natural escapement with central impulses
Winding & setting: Two-position winding stem: Position 1: manual winding
Position 2: setting the time
Finishing: Satin, shot-blasted, Bridges diamond-beveled and drawn out
Power reserve: At least 38 hours
Strap: Brown satin alligator (rose gold version), Black satin alligator (white gold version), Pin buckle made of rose gold or white gold