In the November 2022 issue, marking 100 years since the birth of the automatic watch, the editorial team at Chronos Japan took a serious look at the automatic winding mechanism. We've republished that page on webChronos. This time, we'll be exploring the ratchet winding system, which could be considered the origin of automatic winding, along with IWC's "Pellaton" and Seiko's "Magic Lever."
Photographs by Yu Mitamura, Takafumi Okuda, Eiichi Okuyama, Masanori Yoshie
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]
Considering the automatic winding mechanism from the perspective of the "ratchet"
A simple automatic winding mechanism similar to the switching rocker is the ratchet mechanism, which winds the movement with a pawl. Although it has the disadvantage of having a large dead angle, if it is well designed, it will wind well regardless of the situation. Typical examples are IWC's "Pellaton Automatic" and Seiko's "Magic Lever."
From the birth of the ratchet mechanism to its widespread use
The king of ratchet movements is the Pellaton automatic. The Caliber 52000 series is its perfected form. The basic design and parameters are almost identical to the original. However, the cam, winding pawl, and the intermediate wheel that meshes with them are now made of ceramic, so in theory the automatic mechanism is virtually free of wear. IWC says that there is no need to wind the watch by hand, but if you do wind it by hand, there is no problem at all.
The "origin of automatic winding," adopted by Abraham-Louis Breguet, is the ratchet automatic winding system, which winds the mainspring with a pawl (ratchet). This mechanism, which converts the rotational motion of the rotor into the left-right movement of the pawl, hooking the barrel, was simple and easy for watchmakers to understand. Moreover, since Breguet used it, it was only natural that designers in the early days of automatic winding would also choose the ratchet system. Many half-rotor automatic watches, including the Le Roy from 1922, the Harwood (Fortis) from 26, and the Omega 330 series from 43, share the classic ratchet automatic winding mechanism modeled after Breguet.
Ratchet-type automatic winding movements, which are less prone to wear, were used in high-end watches from the 1940s to the 50s. Chopard's Caliber LUC 96 series (excluding the 96-53) follows in this tradition. The elaborate automatic winding mechanism, reminiscent of Patek Philippe's Caliber 27-460, indicates that this watch is an ultra-high-end watch. However, since it was released in 1997, its winding efficiency is not as high as that of newer models.
However, there was another reason for adopting the ratchet: durability. Automatic movements of this era could not be said to have good winding capabilities, not only by today's standards, but even by the standards of the time. Even the sophisticated Harwood movement is said to have only a power reserve of about 12 hours when using the automatic winding function. As a result, early automatic movements had to be wound by hand frequently to compensate for the lack of winding. Without fear of being misunderstood, automatic movements of this era, with the exception of Rolex, were merely used as a supplement to manual winding. This raised the issue of the durability of the automatic winding mechanism.
The reverser automatic winding mechanism, perfected in the mid-40s, offered better winding efficiency than a switching rocker and greater flexibility in layout than a ratchet. However, when manually winding a watch, the reverser rotated at high speed, quickly wearing out. On the other hand, with a ratchet, only the pawl and the intermediate wheel rubbed against each other, leaving the entire automatic winding mechanism less susceptible to damage. This was likely one of the reasons why various manufacturers continued to develop the ratchet mechanism after the 40s. Omega, Longines, and Patek Philippe all released ratchet automatic movements, with the long-established Geneva manufacturers in particular enjoying great success. However, it wasn't until the IWC Pellaton in 50 and Seiko's Magic Lever in 59 that the ratchet automatic winding mechanism took on its current form.
"Pelaton" and "Magic Lever"
The Pellaton system is a masterpiece of automatic winding that IWC continues to use. When the rotor rotates counterclockwise, the eccentric cam also rotates counterclockwise (red ❶). The ruby comes into contact with the protrusion on the eccentric cam, pushing the rocking bar holding the ruby in the direction of red ❷. When the rocking bar is pushed out, of the two pawls in contact with the transmission wheel, red ❸ pulls the transmission wheel to rotate clockwise (❹), winding the barrel. At this time, the other pawl slides on the transmission wheel. The opposite is true when the rotor rotates clockwise. When the eccentric cam hits the ruby, it pushes the rocking bar in the direction of blue ❷, and blue ❸ pulls the transmission wheel to rotate clockwise (❹). At this time, red ❸ also slides.
The Pellaton automatic winding system was a huge ratchet mechanism, similar to those used by contemporaries like Longines and Patek Philippe. What catches the eye is the heavy rotor supported by a sturdy bridge, and the equally large and heavy ratchet that converts its movement into left-right motion. In theory, winding efficiency decreases as the automatic winding mechanism becomes larger and heavier. Therefore, IWC supported the rotor with a ruby to ensure smooth rotation. Additionally, by adding a suspension to the rotor bridge, they prevented the rotor from breaking, which was a common problem with heavy rotors.
Meanwhile, Seiko's Magic Lever deliberately simplified automatic winding. The original purpose of developing the Magic Lever was to reduce the selling price of automatic watches, which at the time were said to be twice as expensive as manual winding watches. However, by reducing the number of parts and reducing the inertia and resistance of the automatic winding mechanism, the rotational motion of the rotor could be transmitted to the barrel without waste.
The Magic Lever was developed by Suwa Seikosha (now Seiko Epson) in 1959. Its mechanism is very simple: two pawls are always in contact with the transmission wheel, and when one is moving the transmission wheel, the other is kept slipping, keeping the transmission wheel turning in a fixed direction. When the rotor rotates left (❶), the red pawl ❷ pushes the transmission wheel ❸, causing it to rotate left. At this time, the blue pawl ❷ is slipping. Conversely, when the rotor rotates right, the blue pawl ❷ pulls the transmission wheel ❸, also causing it to rotate left. Of course, at this time, the red pawl ❷ is slipping on the transmission wheel. In the diagram, the origin of the power when the pawl pushing and pulling the transmission wheel slips on the transmission wheel is marked as ❶'.
Ratchet automatic winding watches can be classified as "gravity automatic winding," as they wind the mainspring using gravity rather than the rotor's rotation speed. Therefore, the winding efficiency when the rotor continues to rotate at high speed is not as high as that of reversers or switching rockers, which wind the mainspring through the meshing of gears. The "lock angle," during which the automatic winding mechanism does not operate even when the rotor rotates, is also significantly larger than that of reversers or unidirectional winding watches. Of course, this varies depending on the manufacturer, but the lock angle of ratchet watches is generally said to be 40 to 45 degrees, similar to that of switching rockers.
However, with a good design, ratchet automatics offer excellent performance that more than makes up for their various drawbacks. IWC's current Pellaton automatic movement and Grand Seiko's Cal. 9RA2 (and A5) are examples of these characteristics that have been further refined. The surprisingly high winding efficiency of these two movements can be attributed to the smooth rotation of the rotor and the reduced resistance of the automatic winding mechanism.
By ensuring smooth rotation of the rotor and minimizing resistance in the automatic winding mechanism, ratchet automatic winding demonstrates outstanding performance. A good example of this is the Cal. 9RA2 and A5 used by Grand Seiko. Despite supporting the rotor with ceramic bearings and adding an intermediate wheel, the efficiency of the automatic winding mechanism remains at the same level as before.
The advantages of the ratchet automatic winding mechanism outweigh its many disadvantages. It's no surprise that many manufacturers have rediscovered it over the past 20 years. Even with a large rotor, there's no shock when the movement spins idly, unlike with a unidirectional winding automatic. Complicated watches with strong mainsprings and movements with long power reserves will no doubt increasingly choose the ratchet automatic winding mechanism.
This model combines a stainless steel case with a blue dial. It features a perpetual calendar that theoretically requires no adjustment until the year 2100. Since all displays on the dial are perfectly synchronized, the time and calendar can be adjusted simply by turning the crown. Automatic winding (Cal. 52615). 54 jewels. 28,800 vph. Power reserve: approximately 168 hours. Stainless steel case (diameter 46.2 mm, thickness 15.4 mm). Water resistant to 60 meters.
Ratchet information
Employed brands and major movements
IWC in-house movements, Cartier Cal.1904 MC, Cal.1847 MC, Seiko Cal.9R series, Cal.6R series, etc.
Benefits
Fewer parts means less wear and tear. Excellent practical winding efficiency.
Drawbacks
It takes up space horizontally and has a large dead angle, so some know-how is required.
[Overall review]
Although it has many drawbacks, the ratchet type, which uses a pawl to wind the watch, is currently the most popular automatic winding mechanism. The most popular are derivatives of the Magic Lever developed by Seiko. The Richemont Group's Magic Click is one example. While the dead angle is as large as that of a switching rocker, if the design is excellent, it can wind the watch well even during desk work, and there is no shock when the movement spins freely like with a unidirectional winding mechanism. This automatic winding mechanism is likely to become even more popular in the future.
Chopard's prized masterpiece, the Cal. LUC 96.01-L, is thin and uses a micro-rotor for winding, but it employs an unusual cam-based method. The movement works as follows: When rotor ❶ vibrates, a triangular cam, located on the same axis as the rotor, also rotates ❷. The rollers at the tip of the forked winding lever are positioned to sandwich the cam, and are swung back and forth by the cam's rotation ❸. Near the base of the reciprocating winding lever, there is a pair of inverters ❹ (golden parts with pawls), which function as ratchets. These rotate the ratchet wheel by pinching it between them. One of the inverter's pawls presses against the ratchet wheel's teeth, while the other retracts. Therefore, regardless of which way the rotor vibrates, the ratchet wheel, which is transmitted to the barrel, rotates in the same direction.
Asking the brands that use them about the design philosophy behind automatic winding mechanisms
IWC Stefan Ihnen x Caliber 89000 series, Caliber 52000 series, etc.
Born in Switzerland in 1973. After training as a watchmaker, he majored in precision engineering. In 2002, he joined IWC and was involved in movement development until 2006. Since September 2006, he has been head of the R&D department. His main movements include the Caliber 89360.
Rather than categorizing automatic winding mechanisms as unidirectional or bidirectional, we categorize them as either accelerated or gravity winding. The former has a light oscillating mass and requires many revolutions to wind the mainspring. The Pellaton system, on the other hand, is a gravity winding mechanism. This has a large oscillating mass and can generate high torque, allowing the rotor to wind with fewer revolutions. Therefore, the size of the "dead angle," where the rotor moves but the automatic winding mechanism does not, is not an issue.
Calibers 32000 and 69000 use the Magic Click system. The 89000 uses a double pawl winding system based on the Magic Click. The double pawl system is used to reduce the dead angle. Other IWC movements, such as the Caliber 52000 and 82000 series, use Pellaton automatic winding. We chose the Magic Click for the former not because of wear issues, but because it reduced the number of parts and allowed us to make the entire watch significantly thinner.
IWC does not believe that gender-based differences in wrist movements are important. Rather, the key difference is between active and passive wearers. In our experience, the difference between a poorly wound and a very good winding factor is between 3 and 5. However, the 32000 boasts the highest winding factor, ensuring excellent performance even on passive wearers. Furthermore, all winding systems are designed and tested to ensure a 10-year service interval, even on the wrists of sporty wearers.
