Czapek Calibre SHX5 (part two) – the brand’s first Manufacture movement
Czapek Calibre SHX5 (part two). Angus Davies goes behind the scenes to learn more about Czapek’s first Manufacture movement, the Calibre SHX5. This article looks at the appearance of the movement, harnessing energy, transferring energy from the barrel to the escapement and, finally, Angus explores the escapement and the regulating organ.
The Czapek Calibre SHX5 – the appearance of the movement
Xavier had a dream. Firstly, he wanted Czapek’s first Manufacture movement to possess a very transparent design, affording views of numerous components normally hidden from view. He also wanted the movement to make reference to 19th-century pocket watch movements. Finally, he wanted the movement to feature a micro-rotor allowing the wearer to see all of the finissage, the gear train and the balance.
The styling of the movement was designed to encompass an aesthetic tension. On one hand, the bridges and mainplate are sandblasted, imbuing the movement’s appearance with a sense of modernity. However, the movement design also bears a close resemblance to a pocket watch. Indeed, the openworked ratchet wheel, with its 5 spoke design, is reminiscent of the ratchet wheels found on the 3430 Czapek & Cie pocket watch movement.
Similarly, the finger-like bridges, retaining the gear train, reference the aperture found on the oscillating weight fitted to the Calibre SXH3. The open design allows the wearer to see more of the gear train. In addition, the balance bridge is affixed at two points, ensuring greater stability.
Numerous silver-hued screws contrast beautifully with the stealthy tones of the anthracite bridges. While the jewels serve a functional purpose, they also enliven the appearance of the movement, augmenting eye-appeal.
Everything starts with the crown, sometimes referred to as the ‘keyless works’. Interestingly, the device for winding the mainspring and setting the hands was invented by the watchmaker, Jean Adrien Philippe, known as the co-founder of Patek Philippe.
Assuming the mainspring is fully depleted of power, it must be energised by winding the crown. Thereafter, the natural motion of the wearer’s wrist causes the micro-rotor to revolve, tensioning the mainspring.
The beauty of a micro-rotor is that it sits flush with the adjacent bridges, mitigating the movement’s height. The Calibre SXH5 is just 4.3mm thick. Furthermore, unlike a conventional oscillating weight that covers a large portion of the bridges and numerous components below, a micro-rotor allows the wearer to see more of the movement, indulging their mechanical curiosity.
Czapek has endowed the Calibre SXH5 with a micro-rotor formed of 100% recycled platinum. This dense noble metal increases the inertia of the rotor, helping it to efficiently harness the energy created by the wearer’s wrist motion. The potential problem of a micro-rotor is that its modest diameter can lead to insufficient torque being produced. In order to address this issue, Czapek sought the expertise of AB Product, one of the company’s closest partners and a specialist maker of micro-rotors. Indeed, such is the complexity of making a micro-rotor that only a few companies are able to offer this feature.
After the micro-rotor creates energy, it sends the power to the mainspring which sits within the barrel. Sometimes, the layperson assumes that a longer mainspring provides a greater power-reserve, however, sadly things are far more complex than this. The torque supplied by the mainspring should be relatively consistent, irrespective of whether it is fully wound or almost depleted of energy. If this is shown graphically, the torque curve should appear relatively flat for most of the time. As I will go on to explain later, if the power supplied to the escapement is consistent, then the movement will be more precise.
The barrel torque is 8.8 Nmm and the power reserve is over 60 hours. Once again, Czapek procured its barrel from the best in the business, Generale Ressort. This illustrates Czapek’s belief that it is virtually impossible to be the best at everything, hence it makes sense to collaborate with those firms with the requisite knowledge and skills.
Transferring energy from the barrel to the escapement
When the barrel is fully tensioned, there is too much energy to release it directly to the escapement. Like most mechanical watches, the Calibre SXH5 is fitted with a gear train. This consists of four wheels, each engaging with its neighbour via a corresponding pinion. This arrangement is similar to an electrical transformer, stepping down the power to a level that the escapement can cope with.
Gear trains are incredibly complex. The ratios between each wheel have to be carefully calculated. The system must be efficient, with minimal energy loss, otherwise a longer mainspring may be required or the power reserve may be compromised.
Czapek again sought the help of a specialist and chose Atokalpa as a suitable partner.
The bridges are made of a special, hardened German silver (with a value of 200 HV on the Vickers hardness test). By using this material, wear is mitigated. Moreover, the superior torsional rigidity ensures a more efficient transfer of energy and makes it ideal for a sports watch. By adopting this approach, the cost of machining is greater, however, Xavier felt this was worth the extra expense as it helps deliver greater precision and mitigates wear and tear.
The escapement and regulating organ
The gear train transfers energy to the escapement. The escape wheel pushes the pallet jewel affixed to the pallet lever, providing the ‘impulse’. This impulse is a little like pushing a child’s swing, it imparts sufficient energy for the balance wheel to swing clockwise and then counterclockwise.
At the heart of the balance wheel is a hairspring which oscillates at a predetermined frequency. In the case of the Calibre SXH5, the frequency is 28,800 VpH (4Hz). As the balance wheel swings backwards and forwards, the pallet locks and unlocks the escape wheel. It is this repeated action that controls the flow of time, making the hands of the watch advance at the desired speed.
The making of the escapement and, in particular, the regulating organ is not for the inexperienced. At the heart of the regulating organ is the hairspring. This is made of a special alloy, whose precise composition is the subject of much secrecy. Indeed, in the world of watchmaking, the composition of the alloy used for hairsprings is shrouded in the same level of secrecy as the recipe for Coca-Cola.
The alloy is held on reels and passed over a series of rollers and through a number of dies. This process gently stretches the wire and reduces its thickness. It usually takes several days to complete the process. The cross section of the wire must be consistent or the balance will prove impossible to regulate. Eventually, the wire is formed into flat blades, cut to length and baked in a specialist oven. The baking and subsequent cooling of the hairspring again remains a trade secret. The tolerances that a hairspring manufacturer will work to are measured in nanometres (1nm = 0.000001mm). Should the cross section of the hairspring fluctuate, the watch will never deliver precision.
Once the hairspring is made, it must be paired with a balance wheel. This process is termed classage. There will always be very slight variances with both parts, hence each spring is optimally paired. In addition, the balance wheel and the hairspring, once united, are poised. When a car is fitted with new tyres, the rim of the wheel has small weights added ensuring the wheel runs true. Likewise, when the balance is paired with a hairspring, it needs to run free of any unwanted vibration and with a uniform moment of inertia. In order to achieve this, a small incision is made to the underside of the balance wheel to ensure it rotates perfectly.
The Calibre SXH5 is fitted with a variable inertia balance. Most watch movements feature a curb adjuster / raquette instead. This latter system alters the effective length of the hairspring making the movement run faster or slower. While this is the cheapest method of regulating the balance it is not the best.
With a curb adjuster, the hairspring does not breathe as concentrically as with a variable inertia balance, thereby impairing precision. The hairspring passes through two curb pins on what is termed the raquette. When the movement is regulated, the watchmaker moves the raquette towards or away from the stud. The problem with this system is that if the movement is subject to a shock, the hairspring can move, necessitating further regulation.
The approach taken by Czapek brings several benefits. With a variable inertia balance, the effective length of the hairspring remains constant. The rate of the movement is adjusted by altering the balance wheel’s moment of inertia. This is achieved by rotating four C-shaped weights, positioned on each spoke of the balance wheel. These weights are termed masellotes and depending on their position, the movement will run faster or slower.
Furthermore, if the balance is subject to a shock, there is less likelihood of the rate changing. Indeed, speaking to Xavier, one reason for specifying a variable inertia balance and incurring the additional expense this entails, is that during the lifetime of the watch, the movement will require less regulation, mitigating the ongoing expense of ownership.
Another benefit of a variable inertia balance is that a trained watchmaker can fine-tune the regulation of the movement more precisely when contrasted with a simple curb adjusted balance. The masellotes fitted to the balance wheel are positioned in-board, mitigating air turbulence when the balance wheel oscillates to and fro. By reducing the air turbulence, the precision of the movement is enhanced further.
Czapek collaborated with Atokalpa, a firm with vast expertise making cogs and regulating organs. In this instance, the company supplies the escapement, wheels, pinions and inverter.
In my next article (part three), I look closely at finishing, testing and, the future for the Calibre SXH5.