Showcasing the Bernhard Lederer Central Impulse Chronometer

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During Geneva Watch Days, an almost unknown independent watchmaker (for the general public) launched its piece. I am talking about Bernhard Lederer and his Central Impulse Chronometer. Inspired by the work of great watchmakers, including George Daniels and after years of research and development, the watch is an important chronometric evolution and maybe one of the most important works of such from the last years. I present you today the Bernhard Lederer Central Impulse Chronometer as the first in the series dedicated to 2020 GPHG’s nominations.

Hands-on review Bernhard Lederer Central Impulse Chronometer

I had the honour to meet with master watchmaker Bernhard Lederer and his lovely wife during the Geneva Watch Days. In a corner of the Beau-Rivage Hotel lobby, I was fascinated by his stories and his watches. It is not an everyday event to meet someone who impressed George Daniels with his ideas. Behind a modest and humble man hides a genius of our days. Meeting with him was a noteworthy experience.

Bernhard Lederer Central Impulse Chronometer is one of those watches that writes history. The origin of this watch comes from (and here I will quote the Bernhard Lederer website): John Harrison’s constant-force remontoire on his H4 chronometer; Abraham-Louis Breguet’s lubricant-free natural escapement; and Sir John Daniels’ subsequent refinement by combining the natural escapement with the remontoire.

The Central Impulse Chronometer is manufactured in two variants and it is part of the “Tribute to the Masters Of Escapements” collection. The watch is not only a tribute to those great names of horology’s history but also a continuation of their work.

Case and Crystals

Bernhard Lederer Central Impulse Chronometer is presented in two variants: in white and rose gold. The 44mm case comes with a slim design due to a very ingenious construction. Two domed sapphire crystals cover the two-piece construction case.

The caseband is taken to the extreme. Parts of its surface are thinner as even the bezel itself. This construction was possible due to the modern crystal manufacturing capabilities of the present days.

The complex-shaped sapphire surrounds a clever built architectural movement that maximises the use of space.

The relative large 44m size creates an aired view: open, symmetrical, balanced. Note in the picture above the crown and stem integration.

The polished case with subtle yet voluptuous curves is terminated with short, rounded lugs. In the pictures, you can notice two variations of the crown. The watches represent working prototypes and are open to personalisations and design changes.

The concave, convex combination of the bezel and sapphire is sublime. An elegant note that hides the true dimensions of the watch, even if at 12.2 mm, the watch is quite slender – the appearance is metamorphosed.

Two dial variations: open dial & classic

Bernhard Lederer Central Impulse Chronometer comes with two dial variation: the white gold comes with an open grey slate sun-rayed dial, while the rose gold comes in a solid silvered opaline presentation.

Both dials come with leaf hours and minutes hands with SuperLuminova insert. The three-dimensional hours’ indexes are hand applied. The hands and indexes come in the case material.

The running seconds sub-dials are recessed and present a circular pattern. The white gold version has an opening revealing part of the movement. Both variants of the Central Impulse Chronometer have a red seconds’ hands with luminous counterbalance.

Where the magic ends and real science begin

Bernhard Lederer Central Impulse Chronometer is an important milestone in the development of chronometric escapements. The master watchmaker continued the studies of George Daniel. The Caliber 9012 uses two separate gear trains, each with its own barrel.

Each branch has its own 10-second constant force remontoire. In the pictures below can be observed the geometry difference between the approaches of George Daniels and Bernhard Lederer. Moreover, the Lederer escapement works at 3 Hz, in comparison with the 2Hz used by Daniels. This was possible 1.) due to more modern materials used: the escapement anchor and the wheels are manufactured in titanium – lighter, more robust, and 2.) due to optimised geometries.

In the pictures above can be noticed the change in position and geometry for the jewels.

Below some excerpts from the official press release that explain much better all the phenomenas involved in the Bernhard Lederer Central Impulse Chronometer.

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.

The incredible lightness of overcoming inertia
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 strength of soft power
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 Lederer 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.

Acting on ideal impulse
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.

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.

Gently does it
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 hears it.

Unfortunately, the pictures cannot reveal the entire complexity of the movement, but I hope with the above explanations and with the hands-on video, some light will be shared.

One of the most important works in the study of escapements

We are witnessing a new era of chronometry: modern materials and new approaches. Bernhard Lederer and its Central Impulse Chronometer is a further step in the research of the “energy lossless” escapements. This ideal might be never reached, but the journey is fantastic. We can only applaud the determination and assiduous work of master watchmaker Bernhard Lederer. His work can be a fruitful source of inspiration for generations to come. The Central Impulse Chronometer is a fabulous example of exceptional technical design in an appealing presentation. The watch, besides its extraordinary mechanical complexity, is an exquisite and elegant piece.

If we talk from the visual presentation point of view, the Bernhard Lederer Central Impulse Chronometer is a comfortable watch with a charming classic appearance. The watch wears smaller than expected due to its slim bezel and thin body. Both versions tend to have a bit of a sporty allure due to the applied elements and the luminous inserts. But this is perfectly acceptable in these times. While not entering in the dress-watch’s strict canons, the Central Impulse Chronometer will be easily forgiven by any purist – the watch is much too interesting.

Bernhard Lederer Central Impulse Chronometer Technical Specifications

Reference:

9012

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