The Lederer Central Impulse Chronometer is one of the most interesting technical concepts presented recently. Inspired by the George Daniels’ Independent Double Wheel Escapement, revered watchmaker Bernhard Lederer developed a high-performance double-wheel escapement driven by two independent gear trains, each with its own barrel and constant force remontoir d’égalité. Following the presentation of first prototypes about a year ago, the Lederer Constant Impulse Chronometer now comes in its final version. If virtually nothing has changed from a technical perspective, its new dial bringing an elegant new look and an interesting perspective on the movement and its concept.
The basic operating principle of a mechanical movement is the following. Energy is stored by the mainspring inside the barrel. The energy is released via the gear train that drives the hands. The speed at which the gears rotate is controlled by the regulator that comprises the escapement and the oscillator. The escapement transfers energy to the oscillator (the balance wheel and its coiled hairspring) via impulses. In return, the oscillator regulates the escapement. Its oscillations unlock the escapement at a regular rate allowing the gears to rotate and the mainspring to unwind progressively.
Maintaining and counting the oscillations of the watch’s oscillator, the escapement is, without doubt, one of the most complex and fascinating components in a watch. The vast majority of mechanical wristwatches rely on the lever escapement that was invented by British watchmaker Thomas Mudge some 250 years ago. With its simplicity, it is reliable and particularly well suited to serial production. But its efficiency is low; the lever escapement transmits to the oscillator barely a third of the energy it receives from the mainspring.
There are very few other escapements manufactured today. The Omega Co-axial escapement (originally developed with Georges Daniels) has long been the only other escapement that made it to serial production, only recently joined by Grand Seiko and its Dual Impulse Escapement. But over the years, a few watchmakers have tackled the question of the escapement’s efficiency and embarked on developing alternative solutions, which is probably one of the most daunting tasks in the field of mechanical watchmaking and chronometry.
Lederer’s Independent Double Wheel Escapement
Among these recent developments is independent German watchmaker Bernhard Lederer’s unique escapement. One of the first members of the AHCI (Académie Horlogère des Créateurs Indépendants), Lederer made a name for himself with disruptive horological concepts, in particular with the BLU brand. Lederer now mostly acts behind the scene via his company in Saint-Blaise, MHM SA, developing movements and technical solutions for other watchmaking brands… But he is back with watches under his own name, with a captivating piece of horological ingenuity.
The Lederer Central Impulse escapement is inspired by the George Daniels pocket watch Independent Double Wheel Escapement (with whom Lederer exchanged several times), which was the British master’s take on the Breguet natural escapement. Fitted with two escape wheels, this type of escapement is said to be natural because the impulses are transmitted as directly as possible to the balance wheel roller.
If several dual impulse escapements have been designed over the year, the originality of Lederer’s elaborate solution lies in the fact that he installed the two escapement wheels at the end of two separate gear trains, each with its own barrel. Thanks to the two independent gear trains, the two escape wheels do not need to be geared together, making the escapement less complex and more efficient. Additionally, each gear train is fitted with its own remontoir d’égalité to equalize the driving force – in short, a small coiled spring periodically storing and releasing small, fixed amounts of energy. These are mounted on the intermediate wheel (roue de moyenne) and operate in 10-second cycles which, in the words of Bernhard Lederer, allows him to obtain a more stable driving force.
Bernhard Lederer also implemented multiple tweaks to the escapement, making the uniqueness of this Lederer Central Impulse Chronometer. For instance, the escape wheels and the lever are in lightweight titanium. With lower inertia, they are quick to restart and more energy efficient. The shape and geometry of several parts have also been optimized. In particular, the centre “waiting” stone of the detent is slightly rounded, where Daniels used a triangular stone. It aims at avoiding any recoil of the escape wheel in the opposite direction, and at optimizing the timing of the contact between the escapement wheel tooth and the balance wheel impulse pallet. When explaining the sequence of functions of the escapement, Bernhard Lederer refers to an indirect impulse starting the sequence (given via the detent) and preparing for an optimal direct impulse. Last but not least, according to Lederer, this also ensures that the escapement is self-starting.
The Lederer Central Impulse Chronometer in its final form
Following the presentation of the concept about a year ago, the Lederer Central Impulse Chronometer now returns in its final design. This captivating technical concept is still housed in a 44mm case featuring two box sapphire crystals, one at the front and one at the back. This allows keeping a lithe caseband – although the watch is just 12.2mm thick, which is quite thin given the complexity of the movement. The sapphire crystal on the caseback also provides a spectacular view of the splendid movement with its tridimensional architecture and beautiful finishes.
The main novelty for this now-final version of the Lederer Central Impulse Chronometer is its design and its dial, which now features two circular openings, two interlaced circles forming the figure eight. These reveal the most critical and spectacular components of the movement, the escape wheels and the remontoirs. Each aperture is fitted with its own seconds hand, synchronized and progressing in opposite directions. For Lederer, it is also the opportunity to showcase his technical concept in a beautiful way while expressing an original, symbolic vision of time.
The Lederer Central Impulse Chronometer is offered in two 25-piece limited editions in white gold, with a blue dial or with a rhodium-plated dial. The price is set at CHF 128,000.
More details on ledererwatches.com.