Lange presented the fifth watch named ‘Pour le Mérite’ at the Geneva Haute Horlogerie in January. This work combines five complex installations to pay tribute to the classics of classic watchmaking. It is a difficult challenge to assemble a watch factory-made movement composed of 684 parts and equipped with many complicated devices. Only skilled watchmakers can integrate the various devices to make them operate harmoniously and accurately.

Experienced watchmakers have performed many processes of TOURBOGRAPH PERPETUAL ‘Pour le Mérite’ with their own hands.

   ‘Both inside and outside’ can be said to be the creative motto of TOURBOGRAPH PERPETUAL ‘Pour le Mérite’. Looking at five complex functions, two of them are designed to improve the accuracy of travel time. The sesame chain transmission system ensures the stable torque between the mainspring and the balance. This system swings inside the rotating tourbillon frame and is not affected by gravity. The double-tracking chronograph function is classic, controlled by two column wheels. In the space-saving structure, the pointer type perpetual calendar module is installed around the tourbillon.
   The assembly of the movement is much more complicated than it appears to the naked eye. Anthony de Haas, director of product development at Lange, said: ‘Five complex devices can work in harmony, but only the beginning of many processes.’ In fact, each assembly process is different. He states: ‘Even if 684 parts are strictly manufactured within the micron tolerance range, watchmakers still need to make countless fine adjustments to ensure that all devices meet the expectations of the movement engineer.’ He then added: ‘For watchmakers, This requires a superior level of technology, a wealth of knowledge accumulated through experience, manual skills and unusual patience. ‘

Limited edition of 50 TOURBOGRAPH PERPETUAL ‘Pour le Mérite’. Its sapphire crystal caseback presents a chronograph and a tracking hand.
   To make such a delicate mechanical device, we have to rely on a team of experts who have continuously honed and improved their skills through complex clock creations such as the production of RICHARD LANGE PERPETUAL CALENDAR ‘Terraluna’ and DATOGRAPH PERPETUAL TOURBILLON.
The following images show several key processes from hundreds of processes:

Assembling the sesame chain drive system
   After the watchmaker wraps a fine sesame chain around a pre-assembled barrel, the two components can be integrated into the movement. The sesame chain is then connected to the pagoda wheel. Planetary or differential gears must be installed first. Inside the pagoda wheel, the gears ensure that when the watch is wound, the power from the main barrel to the escapement will not be interrupted. The system consists of 38 parts and occupies only 8.6 mm in diameter.

Assembling the sesame chain drive system
The watchmaker uses a ratchet on the spindle of a square barrel to adjust the final tension of the mainspring.

Assembling the tourbillon
   One of the major challenges in making TOURBOGRAPH PERPETUAL ‘Pour le Mérite’ was to assemble the tourbillon. A lot of preparation is required before the delicate components are placed on the basic movement. The long road to success begins with the initial assembly of the individual components. After the initial assembly is completed, adjustment, disassembly, final modification and secondary assembly are required. A swinging tourbillon bridge is suspended between the two diamond end stones to secure the frame to the timing bridge. The new curved design of the tourbillon bridge brings new challenges to grooming experts. The black polishing technology used on the surface of the stainless steel parts allows the incident light to be refracted in only one direction, presenting a delicate bright effect. Only when viewed from a specific angle, the surface will have a shiny specular effect, and other angles will appear bright black.

Assembling the timing and tracking device
   The chronograph and tracking device is located on the side of the movement and consists of a total of 136 parts. During the assembly phase, all parts that make up the column wheel are finely adjusted by hand. This is because the complicated switching operation of gears, levers, mandrels and hairsprings must be accurately operated within a fraction of a second to avoid operational conflicts in mechanical components.

Assembling the tracking wheel
   The tracing mandrel is about one centimeter long and extends from the dial to the tracing wheel on the other side of the movement. Then pass through the hollow chronograph mandrel. The mandrel is made of a round piece of hard steel and is carefully trimmed by hand.

Assembling the catch pin
   Two column wheels control the timing function. One of them is used to transfer the arm of the catch pin. The clamping lever is free-floating, so its arm can be placed in the center of the edge of the chase wheel and clamped from both sides with even pressure. The grip and gear surfaces are finished with straight and round patterns. In order to improve the grip, the fine teeth of the column wheel are specially treated to have a rough feel.

Assembling perpetual calendar and moon phase display
   The perpetual calendar can correctly display the different lengths of months in the Gregorian 100-year cycle. In other words, the perpetual calendar does not need to be corrected for one day until 2100. This is due to the 48-month gear of the perpetual calendar module, which is provided with bump positions every month.
   The seven transmission phases indicated by the moon phases are accurately calculated and only need to be corrected for one day after 122.6 years of continuous operation. The dark blue tone of the white 18K gold moon phase disk is made with a patented coating. Its interference effects, such as filters, can hide all non-blue spectra of incident sunlight. Then use the laser to cut clear stars at the coating.