In the November 2022 issue, marking 100 years since the birth of the automatic watch, the Chronos Japan editorial team took a serious look at the automatic winding mechanism. This time, we've republished a column from this project on webChronos. Learn more about the de-clutch, an important yet often overlooked part, and the MPS ball bearings that advance the winding mechanism.
Interview and text by Masayuki Hirota (Chronos-Japan)
Edited & Text by Chronos Japan Edition (Yukiya Suzuki, Yuto Hosoda)
[Article published in the July 2022 issue of Kronos Japan]
The unique characteristics of automatic watches as seen in the declutch
One component that probably goes unnoticed but is a real headache for designers is the declutch, which separates the manual winding from the automatic winding. This small component strongly reflects each manufacturer's approach to automatic winding.
As a general rule, the Chronos Japan editorial team does not recommend winding an automatic watch by hand. This is because winding an automatic watch by hand puts strain on the automatic winding mechanism. For example, if you manually wind a reverser-type automatic watch, the winding mechanism will rotate at high speed and quickly wear out. This is less likely to occur with the latest Pellaton automatic watches, which use ceramic pawls and intermediate wheels, or reversers with built-in ceramic ball bearings. While we generally do not recommend it, if you do wind your watch by hand, it is best to do so slowly.
The manual winding and automatic winding mechanisms are always connected. If we assume this is the case, then when the automatic winding mechanism winds up, it should also affect the manual winding mechanism. For this reason, almost all automatic winding movements incorporate a clutch, commonly known as a "declutch," that cuts the connection between the manual winding and automatic winding mechanisms. The ETA 2824-2 has a mechanism in which the crown wheel itself slides to cut the connection with the automatic winding mechanism. The thinner ETA 2892A2, Audemars Piguet's 3120 series, and Citizen's 09 series have almost the same mechanism, but have a small de-clutch between the crown wheel and ratchet wheel. This is probably because there is no space.
The most highly acclaimed de-clutch is the eyeglass-type de-clutch used by Rolex and Chopard in some of their LUC collections. Its reliable release system is a bit excessive by today's standards, but it is unique to both companies, who place importance on durability.
Although it may be a simple design, the clutch strongly reflects each manufacturer's philosophy. Should they prioritize thinness or durability? This small part reflects each manufacturer's vision of what an automatic watch should be.
The MPS: A Dark Horse Automatic
Ceramic balls evolve the future of winding mechanisms
Recently, there's a name you often hear from people in the watch industry: "We use MPS parts." MPS, a Swiss bearing company, has been increasing its presence in the world of luxury watches in recent years. But what exactly is MPS?
MPS's "OneWay" reverser has revolutionized the concept of reversers by incorporating a ceramic bearing. The MPS documentation states, "MPS has miniaturized the bidirectional winding concept." The built-in bearing catches and stops the reverser's built-in pawl in one direction, and lets it go in the opposite direction. Theoretically, it can withstand durability tests of over 15 years, and its dead angle is only 7°.
For a long time, there had been no major innovations in reverser automatic watches. However, since the 2000s, new types of reversers have begun to appear. Good examples include Seiko's 9S6 series, which achieved high winding performance despite its small diameter, and Chopard LUC's reverser, which uses a planetary gear. A new addition to this category is the "OneWay" reverser made by MPS of Switzerland. Its main feature is the use of a ceramic ball bearing inside the switch wheel.
Reversers, which use gear meshing to wind the movement in both directions, are highly efficient when they are small, but prone to wear. On the other hand, larger reversers are stronger, but their inertia increases and winding efficiency decreases. So how can durability and winding efficiency be achieved? One of the best solutions at present appears to be the MPS one-way reverser. According to research by the Chronos Japan editorial team, manufacturers currently using this reverser include Richard Mille, Audemars Piguet, and Cartier, with Capek also planning to adopt it in the future. Incidentally, the MPS reverser was also chosen for the bidirectional automatic winding mechanism of the Cartier Mass Mystérieuse, released in 2022. According to a person involved, "Considering the storage space required, there was no other option than MPS."
Ceramic rotor bearings are highly resistant to magnetism and, in theory, have lower resistance, but they also produce more noise. The solution to this problem is ActiVib. The blue material visible around the outer periphery of the shaft is an artificial shock absorber. In the evolution version, which is often used in luxury watches, the blue buffer material is hidden, giving it a more refined look. Although few manufacturers publicly state this, there are many examples of manufacturers that use ceramic bearings adopting it.
The one-way reverser has a built-in ceramic ball that moves freely in one direction while completely blocking movement in the opposite direction. The dead angle when in operation is 7 degrees, which is only about one-third that of the ETA 2892A2. It also requires no lubrication, and will pass tests for at least 15 years under normal use. One-way reversers are an exception to the rule, as they are generally replaced during maintenance.
MPS, which specializes in ceramic bearings, has also tackled the noise issue. They have developed a new mechanism called "ActiVib." MPS explains that "ceramic ball bearings are more efficient, but in some situations they rotate faster and generate noise." They also state that "the oil in steel bearings absorbs some of the vibrations." This means that they are louder than steel. So how can you reduce the noise of ceramic bearings?
Activib is a system in which a shaft with a fixed bearing is supported by a shock absorber made of synthetic materials. Although Roger Dubuis won't say it explicitly, it is this Activib that has enabled the company to reduce the noise of micro-rotors in recent years. Furthermore, in the improved Evolution, the synthetic materials are no longer visible.
ActiGir improves the performance of unidirectional automatic winding. MPS explains that by regulating the movement of the rotor itself, it reduces unnecessary noise and wear. The system itself is similar to the clutch system found in Rolex Caliber NA movements from the 1930s, but is more sophisticated and durable. As with the one-way system, the key is ceramic ball bearings. As with other MPS systems, it is said to last for 15 years under normal use.
I'd like to introduce another interesting attempt. The ActiGir system, attached to the back of the rotor, is reminiscent of the original Rolex Perpetual from the 1930s. This gear allows the rotor to rotate in one direction, but blocks it from rotating in the opposite direction. While this may seem like a rather crude mechanism, it is said to only reduce winding efficiency by a maximum of 5% compared to the same mechanism using conventional bearings.
MPS is taking on the world of automatic winding with ceramic bearings, and will be an essential supplier for any future Reverser watch.
