Who wants a automatic watch If you want to buy a car, you should know how it works and what the differences are between automatic drives. The most important principle is: in order for anything to move at all in mechanical clockworks, it needs power. The same is stored by the tension spring packed in the spring housing. And in a more or less awakened state.
Nothing works without it: the rotor supplies the automatic movement with energy
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What is an automatic?
In principle, the "automatic" in an automatic watch is a normal mechanical movement with an additional mechanism that converts kinetic energy into potential energy. In other words, when the wearer moves his wrist and thus the watch, this movement is used to tension the mainspring. vehicle is gravity, this allows an oscillating mass, whether as a central, three-quarter or micro-rotor executed, striving towards the center of the earth. A small gear chain transmits the resulting kinetic energy to the mainspring barrel.
The new automatic manufacture caliber MT 5813 from tudor
The automatic watch with double-sided winding
Depending on the design of the automatic assembly, the latter consists of two components: automatic watches with bidirectional winding have, first of all, a change-speed gear train. It is its task to rectify the movements of the rotors. Power generation is therefore independent of the direction of rotation. Over the decades, technicians and watchmakers came up with various polarization systems that worked with the help of gears, pawls or eccentrics.
Automatic with bilateral winding: bidynator caliber from felsa
the rectifier pioneer in automatic watches was felsa, a raw-movement manufacturer founded in 1918. in 1942, the company, based in lengnau, switzerland, had leveraged rolex’s patents on automatics with a clever move. With the "bidynator" caliber 692 (diameter 112 lines, height 5.8 mm), the rotor was wound for the first time in both directions of movement of the wrist and wristwatch, i.e. on both sides. The trick: a small rocker, which connected the reduction gear and barrel via one or two gears, depending on the direction of rotor rotation.
Three years later, longines also made its debut with a rotor movement. In view of the legal situation, the manufacture also came up with something new and patent-worthy: the oscillating weight of the self-winding watch also acted on both sides in its 13-ligne, 6.5-mm-high "22 A". The polarization is provided by a so-called eccentric changer and a sophisticated system of switching and locking pawls.
Three years later, in 1948, it was eterna’s turn to take over the watchmaking business. In the case of the grenchners, the engineer heinrich stamm, internally respectfully known as daniel dusentrieb, had the rotor rotate around a miniature ball bearing. Reducing bearing friction and the risk of breakage. In addition, the automatic movements 1198 and 1199 had an equally patented change gear with springless pawls. This efficient system was distinguished by minimal losses during pawl recoil. This was one of the reasons why other automatic watchmakers followed this pioneering path in the decades that followed.
Gear changer of the "bidynator" automatic
Journalists at the time praised the "eterna-matic" as "scientifically the most modern watch and the preferred choice of specialists. The fact that, for the first time in the history of self-winding, eterna had succeeded in combining the self-winding mechanism in a module consisting of a total of twelve parts also contributed to this verdict. After loosening three, in newer calibers even only two screws, it could be lifted off the base movement in less than a minute. Of course, the rohwerke sister eta also benefited from this pioneering spirit. Because eterna wanted to keep its technological lead from its competitors, the eta automatic calibers 1216 and 1256 launched in 1950 had to make do with ratchet wheels, while the oscillating weight rotated around a conical plain bearing.
1944: IWC enters the business with the pellaton winding system
In 1944, the watchmaker albert pellaton to IWC . as technical director, he led the schaffhausen manufacture into the age of the automatic watch. On 7. In June 1950, the company filed a patent application for an invention that was also to make history. the transmission of power from the rotor to the barrel of the automatic caliber 81 as well as the following "85-series" was done in both directions of rotation. This is achieved with the aid of a cam disc and an ingenious pawl system. In the so-called "pellaton" winding mechanism, the latter alternately performs the tasks of winding and backstop.
Patent for the automatic: IWC pellaton winding system
This marked the beginning of a trend: the future of the automatic watch belonged to the bidirectional winding system, because every movement of the carrier arm and thus of the rotor, no matter in which direction, should be used to generate energy for the automatic watch. The construction of the change gears for polarization offered a great deal of design freedom. Gear, pawl and eccentric changers have courted and continue to court the favor of buyers of automatic watches.
The automatic watch with one-sided winding also gains acceptance
Then came 1973, and with it a new chronograph caliber that survived the turmoil of the quartz revolution – during which the mechanical wristwatch nearly died out – without complaint: the valjoux 7750. With it, designer edmond capt had placed particular emphasis on serviceability and energy efficiency. the amazing thing: the rotor of the automatic movement only worked in one direction. Criticism that it does its job inadequately is almost never heard, even from experts. on the contrary: the good winding performance and reliability are praised time and again. This is one of the reasons why this automatic caliber, despite its comparatively simple technology, is today one of the undisputed bestsellers among the movements available for mechanical wristwatches.
A classic automatic: the valjoux 7750 caliber
in 1994, girard perregaux returned to the ranks of manufactures producing automatic watches with the caliber family 3xxx. The basic caliber 3000, diameter 23.9 and height 2.98 mm, belongs to the particularly flat representatives of the species with central rotor. The energy for the automatic mechanism is provided by a ball bearing rotor in one direction of rotation. The decision to dispense with a change gear was made after careful consideration, because the designers felt that only unidirectionally winding rotors would react much more sensitively to the movements of the wrist and the watch.
Jaeger-lecoultre: caliber 975
This view was shared by jaeger-lecoultre, for example, in the 975 "autotractor" launched in 2004, and by patek philippe in the development of the automatic caliber 324. Thus, the question of whether movements with unidirectional or bidirectional winding work more efficiently belongs to the category of scholarly disputes. The valid answer is still a long time coming. Both systems have their advantages and, of course, disadvantages, not least in practice and for the wearers of automatic watches.
The reduction gear: indispensable for the automatic watch
Sliding bridle for the mainspring in movements of automatic watches
in contrast to the change gear, the reduction gear is indispensable in the automatic movement. Its task is to convert the relatively fast rotor movements into slower ones with higher torque. This is what is needed to tension the mainspring.
Because too much of a good thing would be detrimental, the outer spring end is not attached directly to the mainspring barrel. Rather, it hangs on the hook of a sliding bridle, which slides along the inner wall of the mainspring barrel after reaching the predefined maximum tension.
rotor yes, but what cause for discussion are the shape, size and arrangement of the oscillating weight?. Whether central or micro-rotor, each system has its advantages and disadvantages. Supporters of the classic central rotor see no technical reason to use a rotor smaller in diameter and integrate it somewhere in the base plant. Taking, for example, an "el-primero" automatic movement from zenith, the torque of the central rotor can be calculated as follows:
movement diameter : 30 mm
weight of the oscillating weight : 5.95 grams
radius of rotation : 7.34 mm
maximum static torque of the flywheel mass : 43.67 gr x mm
sliding torque of the mainspring : 2.000 gr x mm
If the oscillating weight has the same shape and the bearing is two millimeters off center, it is logical to reduce its diameter accordingly. This leads to the following result:
Weight of the flywheel : 4.73 grams
turning radius : 6.34 mm
maximum static torque of the flywheel : 30 gr x mm
loss of static torque : 31 percent
To compensate for this, a different reduction gear is needed. Depending on the design, the winding process can be slowed down here.
When designing very flat or even ultra-flat automatic movements, designers have since the 1950s resorted to the option of integrating the rotor completely into the movement plane. In this case we speak of the microrotor. Here is an example of the calculation:
weight of the flywheel mass : 2.88 grams
turning radius : 3,57 mm
maximum static torque of the oscillating mass : 10.28 gr x mm
loss of static torque : 76 percent
By calculating the reduction gearbox accordingly, the loss of static torque can be counteracted here as well. Compared to centrally or slightly eccentrically arranged oscillating weights, micro-rotors allow not only a particularly flat design but also an unobstructed view of the entire movement with its decorations as well as the oscillating and escapement system. And especially this is for many lovers of automatic watches and of course also of hand-wound watches a quite serious decision criterion.
Turning over a wristwatch with patek philippe caliber 240 gives a clear view of its oscillating and escapement system
The fact that smaller than central rotors do their job extremely satisfactorily in automatic watches is proven, among other things, by the tried-and-tested automatic movement 240 from patek philippe , the 1.96 by chopard , the RD 77 by roger dubuis , the 1270 by piaget or the sax-O-mat by A. Long& sons .
Chopard caliber L.U.C 1.96
movement is (almost) all in an automatic watchs
Regardless of the size and positioning of the oscillating weight, regardless of whether it is wound on one or both sides, all movements for automatic watches have one thing in common: if they are to function perfectly without occasional manual assistance, they require a sufficient amount of movement, which is supplied to the wristwatch by wearing it or by a watch winder. Because the movement alone generates kinetic energy for tensioning the tension spring. This results in a more uniform drive torque, which in turn can be reflected in better performance of the watch. Glb
For even more information on functions and complications in mechanical watch movements, see UHREN-MAGAZIN special wissen 2020.
Continually updated article, originally posted online in october 2012.
