Bernhard Lederer Central Impulse Chronometer

The Bernhard Lederer Central Impulse Chronometer features two barrels, serving two gear trains, connected to two remontoires both connected to a natural escapement. This incredible tour de force is far more complicated than it may first appear and is the latest creation by German watchmaker, Bernhard Lederer.

Until a few weeks ago, to my shame, I did not know anything about Bernhard Lederer or his body of work. Recently, I was offered the chance to interview Bernhard and, after reading a little bit about him, I agreed to have a chat. Bernhard is German albeit he has spent over 20 years living and working in Switzerland.

Bernhard is a founding member of the AHCI (Académie Horlogère de Créateurs Indépendants), an association that promotes independent watchmaking. Its members, there are 29 in total, include some of the biggest names in the watch industry, such as Ludovic Ballouard, Felix Baumgartner, Konstantin Chaykin, Philippe Dufour, François-Paul Journe and Andreas Strehler.

In his early career, Bernhard was an apprentice, working for a private museum in Germany, the Wuppertal Watchmaking Museum, restoring and repairing clocks and watches. Unfortunately, having completed his apprenticeship, Bernhard found the watch industry was in the midst of the so-called quartz crisis and most firms had little appetite for recruiting new staff. Therefore, he chose to devote his time working for auction houses and private collectors.

It wasn’t long before Bernhard came to the realisation that he was capable of making many watch components and, therefore, began to ponder whether he could make a timepiece for his own personal enjoyment. He made his dream watch and on completion, one of his clients saw it and immediately commissioned Bernhard to make him a similar watch ‘with a few more complications’.

In the past, Bernhard owned the BLU brand, known for making distinctive watches with off-centre displays. However, these days he is incredibly busy undertaking various projects for the watch industry. His company, MHM, offers an array of services from development, prototyping to making small numbers of watches, such as limited-edition models, for the big brands. Everything is discreet and low-key with no mention of his customers’ famous brand names. It would seem client confidentiality is not merely the preserve of Swiss banks.

After chatting for a short while, and despite his endearing modesty, I quickly realised Bernhard Lederer is a remarkable watchmaker. His overriding obsession is the escapement mechanism and recently he created a watch with a ‘natural escapement with central impulses’, the aptly named Bernhard Lederer Central Impulse Chronometer. This model will be limited to 50 pieces.

Bernhard Lederer Central Impulse Chronometer

However, this new model is the just first chapter of the ‘Tribute to the Masters of Escapements collection.’ Indeed, Bernhard plans to release ‘eight chapters’, each endowed with a different type of escapement. This sounds like a tantalising prospect for any self-respecting watch aficionado.

Returning to the Bernhard Lederer Central Impulse Chronometer, there are two versions, one in 18-carat rose gold and a second in 18-carat white gold.

The dial

Depending on the case material selected, the Bernhard Lederer Central Impulse Chronometer is supplied with a solid dial (rose gold case) or partially openworked dial (white gold case). The unusual hour and minute hands are the same on both variants and could best be described as hybrid hands, a fusion of traditional leaf-shaped and baton-style hands. Both dial options also feature applied indexes and a crisp minute track. The hands and indexes are lined with Super-LumiNova. While luminescent treatment is often associated with sporty watches, its use seems fitting for this ‘dressy’ composition.

Bernhard Lederer Central Impulse Chronometer

A small seconds display sits lower than the main dial epidermis and is positioned between 8 and 9 o’clock. On the solid dial version, the entire small seconds display is snailed. However, on the slate grey openworked dial, a snailed track frames the display with the central area of the display left open, affording views of the movement below. The small seconds display on both dial versions features a red hand with a prominent counterweight.

Bernhard Lederer Central Impulse Chronometer

When appraising each version of the watch, the solid dial, with its silvered opaline finish has a classical appearance, while the slate grey openworked dial with its sunray decoration looks more contemporary. Certainly, both dial options exude grace and an extraordinary quotient of refinement.

Interestingly, as I chatted to Bernhard I noticed him use his hands to describe design details. This prompted me to ask who designed the watches. Bernhard replied, ‘I had some help from designers, but 80% of the design is me.’ It seems that Bernhard is not only a great watchmaker, but he is obviously an aesthete with a well-developed eye for detail.  

The case

Measuring 44mm in diameter, with a case height of 12.2mm, the case is generously proportioned, however, considering the complexity of the movement it could have easily been much larger. As stated earlier, the Bernhard Lederer Central Impulse Chronometer is offered in two case variants, 18-carat rose gold or 18-carat white gold.

Bernhard Lederer Central Impulse Chronometer

Unusually, half of the case is formed of sapphire crystal, surpassing the usual circular pane of crystal found on the caseback of many watches. The crystal has rounded sides providing incredible lateral views of the movement. It’s obvious that it was costly to produce, however, Bernhard doesn’t strike me as someone who subscribes to penny-pinching.


Bernhard Lederer Central Impulse Chronometer

At one stage, I quizzed Bernhard about the case design. His answer was illuminating, ‘A very important aspect of design is to explore the limits of what is possible.’ Looking at the case and listening to the Swabian watchmaker, it is clear that he does not countenance the notion of compromise. Furthermore, it is obvious he obsesses over the smallest of details. 

Bernhard Lederer Central Impulse Chronometer

The bezel is comparatively slim and the lugs are incredibly short, drawing the strap close to the watch head. It seems that everything has been pared back to the minimum size in order to afford greater room for the dial to shine. The crown has a distinctive 2-rows grip and is adorned with a stylised ‘L’ on its vertical flank.

The movement – a natural escapement

Most mechanical watches feature a Swiss lever escapement as it is comparatively simple, robust and relatively cheap to produce. With this system the energy is transferred from the mainspring to the escapement, via the gear train. The gear train is not 100% efficient as energy is lost due to friction etc.

This energy loss pales by comparison with the inefficiency of the Swiss lever escapement itself. This is because the power supplied to the escape wheel has to be transmitted via the pallet lever, interfacing with the impulse jewel in order to propel the balance wheel. Another problem with a Swiss-lever escapement is that it requires lubrication, however, this lubricant inevitably deteriorates with time, necessitating replacement.


Bernhard Lederer Central Impulse Chronometer

As the escapement is responsible for the greatest energy losses within a movement, optimising the design offers the largest potential gains. Indeed, by optimising the escapement, the power-reserve can be increased and precision can be improved.

With this in mind, Bernhard Lederer chose to revisit Breguet’s échappement naturel, the natural escapement, where the escape wheel teeth deliver impulses directly to the balance axis. By adopting this approach there is no requirement for lubricant. A natural escapement features two escape wheels positioned adjacent to each other. One escape wheel is driven by the gear train and subsequently drives the second wheel.

Bernhard Lederer Central Impulse Chronometer

While the natural escapement offers useful benefits over a Swiss lever escapement, it is fraught with technical obstacles. Most of the existing Breguet-type natural escapements use a large number of components, which increases the weight and thus the energy required to power the timekeeper. Indeed, Breguet abandoned the system circa 1810 and redirected his gaze back to lever escapements.

Undeterred by Breguet’s experience, George Daniels famously used a natural escapement in his Space Traveller I and Space Traveller II pocket watches. Although Lederer, is a huge fan of the late George Daniels, the Englishman’s version of the natural escapement was not suitable for a wristwatch application. As Lederer explained, ‘It operated at a very low frequency, below 2,5 Hz and was not self-starting, making it necessary to shake the watch to get it going.

Therefore, the Swabian master watchmaker, recognising the deficiencies of previous natural escapements, looked to increase the frequency to 3Hz in order to improve shock resistance and precision.

The German watchmaker has refined the design of the natural escapement. Instead of using steel for the escape wheels, Bernhard chose to make them from hardened titanium, thereby mitigating mass. In order to increase the frequency of the movement, the force sent to the balance wheel has been increased. Ordinarily, this would cause the escape wheel teeth to strike the pallets with greater force, something that would not be helpful. Indeed, as Lederer explained, fewer shocks between the components leads to a smoother transfer of energy.

Ingeniously, Bernhard revisited Daniel’s design, changing the angle between the balance axis and the respective escape wheels, from 100° to 120°. This centralises the impulse to the balance, ‘bringing it closer to the front’. By producing the impulse much earlier, it culminates in a softer, smoother transition of energy. This mitigates energy consumption, ameliorates the influence of shocks, enhances isochronism and improves rate stability.

Furthermore, Lederer has equipped his model with two gear trains each fitted with a constant-force remontoire in order to stabilise the power delivered to the escapement. Interestingly, the 10-second remontoires are arranged such that every 5 seconds one remontoire unleashes its power, pulses its associated escapement with a dose of energy and provides a hushed, barely audible, magical sound.

Most watches are regulated using a Witschi machine which is fitted with a sensitive microphone that effectively listens to the movement. The device measures the rate accuracy, amplitude and beat error. However, the Bernhard Lederer Central Impulse Chronometer has a ‘phonetic signature’ that is very different from what traditional control machines are accustomed to analyzing, hence they are unable to handle this particular escapement. Therefore, the rate is regulated using a laser-based measurement instrument which is able to record the rate and amplitude throughout the day, allowing Bernhard to scrutinise the behaviour of the movement at various points during a 24-hour cycle and make adjustments accordingly.

The movement – other details

The hand-wound movement, the Calibre 9012, is equipped with two barrels, each serving their own dedicated gear train.

Interestingly, despite the complexity of the movement, there are only 208 components, a characteristic which reduces mass and thereby energy consumption.

Unlike many contemporary watches where oversized bridges hide many of the movement parts from view, Bernhard has chosen to disclose virtually every part. He has used slender, finger-like bridges which afford sight of the various wheels in motion. These slender bridges are shotblasted, engraved and grained. Sublime anglage is much in evidence with numerous gleaming interior and exterior angles. Several wheels feature an unusual ‘tangent curve’ design, another hallmark of the Bernhard Lederer brand. Both the mainplate and bridges are made of German silver, free of any rhodium treatment. Matte and mirror polished surfaces are juxtaposed throughout.

Put simply, the finissage is exemplary.

Closing remarks

The Bernhard Lederer Central Impulse Chronometer is extraordinary. Beyond its pure complexion and prepossessing beauty, it is blessed with remarkable mechanical intellect.

The dial is clean and free of superfluous detail, especially the solid, silver opaline option. Personally, I would probably select the slate grey dial with its openworked section, eager to quaff as much mechanical detail as humanly possible.

When appraising this horological composition, some commentators may describe it as simple. However, there is nothing simple or ordinary about this watch. It is rich with subtle details. The bezel and lugs are pared back in order to grant a larger area for the dial. Close examination of the crown reveals a pleasing design that has been engineered to be easily manipulated. Indeed, the Swabian watchmaker has considered each detail to the nth degree while his aesthetic sensibilities are notably well developed.

While Bernhard is a charming chap, I suspect he is a tough taskmaster. With his eye for the minutiae and his overriding pursuit of perfection, I think he must struggle with the notion of mediocrity. Approximately 50% of the case is sapphire crystal. It is not a flat pane but a curvaceous housing that will have been very costly to produce, however, the resultant appearance proves exquisite. Moreover, in exposing more of the movement, there is a greater imperative to execute each disclosed part to a flawless conclusion.

However, all roads lead me to Bernhard’s natural escapement. He has invested vast amounts of time mastering an escapement that has previously frustrated some incredible watchmaking talents. The resultant movement, the Calibre 9012, delivers chronometric precision, merely sips energy, provides rate stability and does not require lubrication. Most of all, this movement is suited to use in a wristwatch.

The Bernhard Lederer Central Impulse Chronometer cannot be described in a few sentences. Indeed, the complexity of this watch cannot be overstated and to fully appreciate its importance, the model requires a reasonable understanding of watchmaking. However, once a person is able to comprehend the challenges Bernhard has overcome in order to create this watch, then they will appreciate his greatness.

A few weeks ago, I did not know of Bernhard Lederer, however, now having spoken to this watchmaking genius, I can safely say, I will never forget him. 

Further reading

Technical specification

  • Model: Bernhard Lederer Central Impulse Chronometer
  • Reference: 9012
  • Case: 18-carat rose gold or 18-carat white gold; diameter 42 mm height; height 12.2 mm; water resistance 3ATM (30 metres); sapphire crystal to front and exhibition caseback
  • Functions: Hours; minutes; small seconds
  • Movement: Calibre 9012; hand-wound movement; frequency 21,600 VpH (3Hz); 45 jewels; power reserve at least 58 hours; components = 208
  • Strap: Colour-coordinating satin alligator strap with matching 18-carat gold pin buckle
  • Price: CHF 128,000 excluding tax (RRP as at 19.8.2020)

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