We take it for granted that our watches can always tell the time accurately. But before this could happen, the existing mechanics of large grandfather clocks had to be refined. Today we’re taking you through some exciting moments in watch history to give you an insight into how the balance wheel was created, and how it works.
What is the balance wheel of a watch?
The balance wheel is a finely crafted wheel that is part of the balance spring oscillation system. It’s mainly used as a rate regulator in wrist- and pocket watches. This delicate, compact mechanical system ensures the correct beat and precision of our watches, and is often referred to as the “heart” of a watch due to its important function. The balance wheel oscillates at a certain frequency (oscillation period) and, together with the escapement, ensures that the gear train inside the watch is partially stopped and released. This largely position-independent movement is indicated by the clock hands, which are connected to the gear train.
Technical Developments for Greater Precision
The biggest challenge in establishing the wrist watch was guaranteeing its accuracy. Tower clocks and grandfather clocks had already achieved a certain reliability in telling the time thanks to their escapement in the form of a pendulum. The so-called pendulum law goes back to Galileo Galilei, who established that the duration of a pendulum’s oscillation is determined by its length. The oscillation period of a pendulum about one meter long is one second. However, the accuracy of the watch became more difficult as soon as the wearer started to move their wrist. The technology of the large clock movements could not of course be packed directly into pocket watches. One of the first portable clocks was finally produced by Peter Henlein, a master locksmith and clockmaker from the 15th century, in Nuremberg, Germany. To do this, he used so-called torsion pendulums, which perform a circular movement using a rod with two weights that transfer their energy to a spring. Although the torsion pendulum made these watches considerably smaller, they were still very susceptible to malfunctions when worn. This problem was only solved in the 17th century by two men. Jean de Hautefeuille, a French priest and inventor, and Christiaan Huygens, a Dutch astronomer and mathematician, discussed the possibility of improving the mechanism for regulating the rate by developing the balance wheel with a hairspring. Huygens built the mechanism and received a French patent for it in 1675. The principle, constantly improved upon to this day, is still used today in pocket watches and wristwatches.
Structure of the Balance Wheel Oscillation System
As mentioned, the balance wheel is not a single piece, but instead several fine individual parts that form the oscillation system of a watch. The balance-spring oscillation system includes the balance wheel, a thin wheel in which the balance spring is installed. This spring is also known as a flat spiral, and is one of the inventions that go back to Huygens. Another form of hairspring can be found in Rolex watches, which can be traced back to one of the most influential watchmakers in history: the famous designer Abraham-Louis Breguet. The hairspring he invented is characterized by better accuracy. However, it is also more complex to manufacture, which is why Huygens’ flat spiral has become widely accepted. To ensure that the hairspring maintains its predetermined rate, it is regulated by the so-called retractors. The balance wheel and hairspring lie on the balance arbor, the fourth component of the balance oscillation system. This very fine rod is only slightly thicker than a human hair and therefore very susceptible to breakage. A number of safety precautions make it more resistant to impacts: The ends of the shaft, the so-called trunnions, are shaped like trumpets and prevent a possible breakage due to this wedge shape. These pins are in turn located within the shock protection and mounted between synthetic rubies. The shock protection ensures that the end of the balance wheel arbor has enough room to move in the event of vertical or horizontal shocks, and is framed in such a way that it does not hit other components. The accuracy of the balance wheel is further improved when it is embedded in a tourbillon. This compensates for the possible influences of gravity by distributing them evenly between the balance wheel and hairspring.
Watches With An Open Balance Wheel
Because the balance wheel is such an important part of the movement, some watch manufacturers give it its own stage in the form of an open balance. With a wristwatch with an open balance wheel, the observer can not only read the current time, but also see the heart of the watch at work. In this kind of watch, there is a recess in the dial that provides a view of the balance wheel. If larger parts of the movement or even the entire inside of the watch are visible, it is referred to as a “skeletonized” movement.
The first watches with an open balance wheel were created in the 1970s in response to the growing desire of some watch fans to get a glimpse of the working movement. Although models with visible movement components are usually even more time-consuming to manufacture than conventional wristwatches, this does not necessarily have to be reflected in a higher price. The following automatic watches with an open balance wheel illustrate how different the prices for such models can be: While the Jaeger-LeCoultre Master Grande Tradition (ref. 5082420) currently costs around $52,000 on Chrono24, models such as the Baume & Mercier Clifton (ref. 10448) start at around $3,150, while the Hamilton Jazzmaster Open Heart (ref. H32705141) from $950 offers a comparatively affordable price and an equally fascinating view of the balance wheel inside the watch.
A mechanical work of art: the double balance wheel
In the luxury watch industry, there are manufacturers who always have to go one better. For example, Audemars Piguet has taken the balance wheel system to a new level, creating a watch with two balance wheels: the Royal Oak Audemars Piguet Royal Oak Double Balance Wheel Openworked. Thanks to the transparent case back, the double balance wheel on this skeletonized wristwatch can even be observed from both sides. In this model, the engineers added a second balance wheel and a second hairspring to the same axis, thus improving precision even further. This arrangement is patented as “Dualbalance” and once again demonstrates the watchmaker’s expertise.
Instinct for Assembly
Anyone who decides to buy a special watch expects a reliable timepiece with a high degree of accuracy. Especially after the advent of quartz watches, manufacturers of mechanical watches can now set themselves apart by the fact that their luxury timepieces run with the highest precision, even without the use of batteries, thanks to watchmaking expertise. An important work step in this context, which particularly affects the balance wheel, is the watch’s position when off the wrist.
How is the balance wheel of a watch adjusted?
Regulation is the term used to describe the fine adjustment of a watch. Timepieces should run smoothly regardless of their position or the outside temperature. The frequency of the balance wheel is adjusted by bending, lengthening, or shortening the hairspring. During assembly, the watchmakers use a timegrapher to measure and display the oscillations of the movement. These values can be used to determine whether the spring has been inserted correctly, whether it needs to be extended, or whether material needs to be removed. This process is carried out during the manufacture of the balance wheel and hairspring as well as at the end of the construction.
