Perpetual Rotor – Rolex

Perpetual Rotor
Freedom, Eternity, Movement


Fundamental component of every Oyster and Rolex signature piece par excellence, the Perpetual rotor, which has marked the history of modern watchmaking, celebrated its 80th anniversary in 2011. By capturing the energy generated by even the slightest move of the wrist, this self-winding system invented by Rolex in 1931 breathes life into the movement so that the heartbeat of the watch never stops. And it creates a direct, personal link between the wearer and the watch.


When a watchmaker opens the case of an Oyster watch, the first thing he sees is the Perpetual rotor: a half-moon-shaped weight pivoting freely on a central axle. The self-winding mechanism, intermittently hidden or visible as the weight rotates, allows on most calibres fleeting glimpses of the famous revers-ing wheels whose characteristic red colour contrasts with the golden colour of the other wheels. On the oscillating weights of the chronograph movements, he can also read, engraved in capital letters, the name of the model – DAYTONA in red letters, YACHT-MASTER II in blue letters. The harmony of the shapes and colours is striking, the quality of the finishings impeccable. Because, even though concealed inside the case of the watch, this complex device reflects the brand’s trademark elegance.





To look carefully at this rotor with its clean lines is to appreciate eight decades of a major chapter in watchmaking history written by Rolex. In 1931, the brand invented this legendary system that gives life to the movement of the self-winding wristwatch, thus revolutionizing the entire watchmaking industry. A technical feat, a masterstroke – words of praise have never been lacking to describe the astounding repercussions of this decisive innovation, which is at the very origin of self-winding mechanisms on modern watches.




Particularly ingenious, the principle of the Perpetual rotor has remained unchanged in the course of various evolutions and successive improvements: with the slightest wrist movement, the half-moon-shaped component – the oscillating weight – pivots freely and silently on its axle driven by the Earth’s gravity. The kinetic energy generated by the rotations of this weight is transmitted via the wheels of the winding mechanism to the mainspring, which is constantly being wound. As long as the watch is being worn, the spring stores and “perpetually” releases the energy necessary for the functioning of the mechanical movement. For increased efficiency, the winding takes place regardless of the direction of the rotation, thanks to the remarkable red reversing wheels introduced in 1959, which have become a distinguishing characteristic of the Perpetual rotor.


Once the maximum tension of the spring is reached, a clutch system stops the winding, preventing damage to the mainspring by overwinding. When the watch is not being worn, the fully wound spring provides a power reserve of two days, and up to 72 hours for the Cosmograph Daytona, Sky-Dweller and Yacht-Master II models.



The Perpetual rotor provides three major advantages for wearers: it liberates them from worrying about manually winding their watch, thus affording additional comfort and freedom; the self-winding system continuously winds the mainspring, thus ensuring greater regularity and better precision of the watch’s regulating organ; finally, the waterproofness of the case is significantly reinforced since daily unscrewing and re-screwing of the winding crown – which, over time, cause wear and tear on the waterproofness system – are eliminated. In addition to these three benefits, there is a fourth, albeit more abstract and emotionally important: that of owning a watch which, as if by magic, counts off seconds and minutes, hours and days, without ever stopping. An intimation of eternity creating an invincible link between the wearer and his or her timepiece.



It is difficult to imagine what a considerable step forward the invention of the Perpetual rotor represented in its day. Within some 20 years between the first chronometer certificate granted to a wristwatch in 1910, the invention in 1926 of the Oyster, the first waterproof wristwatch, and the creation of the modern self-winding watch in 1931, Rolex and its founder Hans Wilsdorf revolutionized watchmaking three different times, proving that a wristwatch could be precise, robust and waterproof, and also “perpetual”. The Perpetual rotor, in a way, constitutes the perfecting of the concept of the Oyster, because it improved its precision and waterproofness while bringing additional comfort and freedom.



With the Perpetual rotor, Rolex found the best solution to a problem that had long concerned watchmakers. The invention around 1770 of a self-winding pocket watch, whose winding was carried out via a rotor system with an oscil-lating weight that captured the energy generated by the movements of the wearer, is credited to Abraham-Louis Perrelet or Hubert Sarton (experts differ on this subject). But the movements of the wearer had little influence on a pocket watch. In attempts to improve the winding yield, systems using alternat-ing movements were developed. Among them, a system in which the path of the weight was limited by stops which it struck and from which it rebounded to amplify the back-and-forth motion.

It was such a system that an English watchmaker named John Harwood transposed for the first time to a wristwatch in 1924. Although it was efficient for pocket watches, the winding based on stops was too rough and therefore inappropriate for a wristwatch. The founder of Rolex had the ingenious idea to ask his technical team to adapt to the wristwatch the self-winding system with a rotor pivoting freely 360° without jolting, which he realized would be much more suitable for a watch worn on the wrist. After years of research and devel-opment to achieve a reliable and efficient result, Rolex perfected the Perpetual rotor in 1931.



The result fulfilled all hopes: as soon as it was introduced, the Perpetual rotor enjoyed a phenomenal success and became the symbol of watchmaking excellence. Patented, the self-winding system remained an exclusive Rolex asset until 1948 and contributed, along with the Oyster case, to establishing the brand’s reputation. Once the patents expired and the invention fell into the public domain, it was adopted by the entire watchmaking industry, which quickly made the principle its own. A noble destiny for the invention that makes the Oyster’s heart beat with each and every movement of its wearer. For more than eight decades already, and for a very long time to come.



Several parameters are critical for the rotor to yield the full measure of its winding power. First, the oscillating weight must be as heavy as possible. To accomplish this, Rolex generally uses a particularly dense tungsten alloy, thus ensuring a rotor with excellent dynamic properties in spite of its small dimensions. Next, the center of gravity of the weight must be as peripheral as possible and its motion must never be impeded by the movement or the case. Finally, the watch must be wound as quickly as possible, without being over-wound, because on an active wearer – a sportsperson, for example – the clutch system preventing over-winding of the spring would be too often brought into play. If you consider that there is a factor of 300 between the movements made by a wearer who is jogging and those of a wearer sitting at his desk all day, it is easy to imagine the delicate balance that must be achieved so that the winding mechanism remains reliable in all circumstances.



At the Bienne site, the various components of the self-winding system are manufactured and assembled. Each one is first shaped, then machined. Each is checked, controlled, inspected. Because every little detail is important, in Bienne as everywhere in the company, a taste for beauty and a passion for detail motivate each workshop. For example, the two eloxed aluminium reversing-wheels are carefully paired to present the same shade of red. Next comes the assem-bly of the various components of the winding mechanism. Once again, there is a careful control, notably of the endshake (the axial play between the ends of the moving parts and the surfaces of the bearings, or jewels), which must be between 15 and 45 microns. This step is entrusted to a machine under the supervision of an operator whose eye is trained to detect any deviation. Experience and expertise also play their roles in the lubrication of the winding mechanism, an extremely delicate process performed using tiny needles and requiring an almost constant human presence at the machine. In another workshop, technicians assemble the oscillating weight, which is then connected to the winding mechanism. At the end of these numerous operations, the rotor comes to life. One last check ensures that the mechanism pivots freely and that it is aesthetically perfect.



The rotor then leaves Bienne for the Acacias site in Geneva. There, during one of the last procedures of what is known as the final assembly of the watch, it is fitted onto the movement, which is already in the case. The freedom of rotation is checked and the case back is screwed on. Afterwards, the rotor, no longer visible, undergoes the Cyclotest, the last test designed to verify its winding power, in other words its capacity to capture and store energy from wrist movements. To do this, the watch, held on a stand, is subjected to slow rotation in both directions for 27 minutes. In this amount of time the mainspring should be sufficiently wound to ensure the proper functioning of the movement for at the very least six hours.