The Essential Components That Make Up the Mechanical Movement of a Modern Wristwatch

Thanks to transparent casebacks and hypnotising inner workings, the components that contemporary wristwatches can’t do without are truly a sight to behold. 

The movement, or alternatively called the calibre, of a timepiece functions like a beating heart, where it regulates the precision and provides the impetus for the hands to keep turning. The incorporation of a movement is the sine qua non of a mechanical wristwatch.

Generally consisting of hundreds of parts, the number can add up in correlation with complexity, such as when inflating the types of complications. In watchmaking, the term complication recalls any feature beyond the display of hours, minutes and seconds. A chronograph or calendar is considered a complication, for example.

In haute horlogerie, a timepiece amalgamating several complicated features, including perpetual calendar, striking mechanism (as seen in minute repeaters), moonphase indicator, flyback chronograph, tourbillon and other advanced luxuries not commonly employed, is called a grand complication.

More than that, timepieces have transcended the utilitarian purpose of timekeeping; they are wearable art. In that regard, not only is the movement a functional requisite, but the level of craftsmanship entailed in its production is also what separates the cream from the crop. Savoir-faire can also be expressed through innovative solutions.

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Learning the A to Z of movement components 

Although design may vary thanks to numerous improvements over the years, a number of components are universally present in a movement. For starters, the mainspring barrel acts as the power plant, storing the kinetic energy generated by winding the crown or an oscillating rotor, thereby tightening the coiled spring. As it unwinds, energy is released, and it creates torque which is then transmitted to help drive other components. An automatic movement relies on the rotor to help wind the mainspring automatically through the wearer’s motion which spins the rotor, while a hand-wound movement is built sans a rotor, hence it relies on the wearer to periodically wind the crown to replenish the energy supply. The rotor is known alternatively as the oscillating weight.

The stem bridging the crown and the movement holds the key to translating the input from the wearer to the turning of the wheels. On a non-screw-down crown, the mainspring can be tightened by turning the crown repeatedly upwards. The crown can be pulled out to adjust the time or the date. On the other hand, on a screw-down crown, the crown must be pulled out to the first position to recharge the mainspring and a further pull for the time or date. This form of engagement is also known as keyless works as the method (via the stem) has superseded the erstwhile use of an additional tool – the key – to help wind the watch or adjust the hands.

Thanks to the prevalence of skeleton watches and transparent casebacks, the inner workings of modern wristwatches can now be admired up close. The ratchet wheel, which sits atop the mainspring barrel, is the most noticeable component due to its massive size, along with the gyrating balance wheel and the golden gear train. The mainspring is coiled around the axle called the arbor, while the ratchet wheel is attached to the arbor via a screw. When the mainspring is fully wound, it hugs the arbor closely.

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Although the mainspring is usually the only source of power for mechanical wristwatches, in rare instances, select wristwatches are fitted with a remontoire system. It is a spring within the powertrain doubling a secondary escapement for the mainspring to help deliver a more consistent rate of torque to the balance wheel, therefore better regulating the consistency and hence the wristwatch’s accuracy.

The escapement is akin to a brake. It pauses and releases the energy at a steady rate from the mainspring. It facilitates the gradual unwinding of the mainspring, allowing the gear train to advance by a small degree each time. Without it, the mainspring will unravel uncontrollably. With it, it allows the wristwatch to tick and tock, so to speak. The gear train is an assemblage of wheels acting as a conduit that transmits power from the mainspring to the escapement, balance wheel and complications via a continuum of toothed wheels and pinions. Each wheel shoulders a different responsibility but works in concert.

OMEGA elucidates the technical achievements behind its Co-Axial escapement.

As a regulating organ, the escapement comprises an escape wheel, a lever and a balance wheel. Some watch brands have adapted the system to suit their own needs and requirements. OMEGA’s proprietary Co-Axial escapement is one of the examples. As the final cog in the escapement, the escape wheel interacts with the lever’s pallets, feeding impulses to the balance wheel. The balance wheel, whose motion is governed by a hairspring, oscillates at a predetermined frequency and moves the lever back and forth constantly.

The hairspring’s conduct has an unrivalled bearing on the precision of a wristwatch. Its width, length, weight, shape and mounting position are tuned to achieve isochronism, in other words, to keep accurate time. Due to external factors that might impose on their sensitivity, the balance wheel and the hairspring have experienced a myriad of material innovations, with watch brands introducing frictionless, anti-magnetic and thermally stable alloys and composites including Nivarox and silicon.

When a wristwatch runs too fast or slow, such deviation can be corrected usually by adjusting the regulator, which is a lever mounted on the balance cock. By sliding the lever, the effective length of the hairspring can be altered, therefore increasing or reducing the balance’s oscillation rate. Some wristwatches may not be equipped with a regulator at all. Instead, to adjust the oscillation rate, the timing screws on the free-sprung balance wheel need to be corrected.

For most conventional wristwatches, all these mechanisms are anchored by a mainplate. Bound together with bridges, these vital parts are provided with a sturdy structure, which often is uplifted with a melange of decorative motifs such as Côtes de Genève, perlage, engravings and sandblasted finish for an artistic exclamation. Screws too may also be afforded an extra heat treatment to turn them blue, whereby the process also strengthens them to better withstand wear and tear.

The number of jewels employed in a movement is always specified by the watchmaker. Though attractive, these rubies or sapphires are used as bearings in mechanisms to smooth friction where components are known to interact with each other religiously. Bevelling and chamfering techniques, which impart soft edges, are also called upon at times to increase the aesthetic appeal of a movement.

Other noteworthy complication-specific components

Beyond the standards, an assortment of specialised components are used in respective complications. In a chronograph movement, wearers will encounter a column wheel or a cam-actuated variety. The cam is capriciously shaped, while the column wheel is conspicuously turret-like.

The tourbillon was patented by Abraham-Louis Breguet in 1801 to alleviate the adverse effects of gravitational pulls on the precision of wristwatches. Since his ground-breaking innovation, other watchmakers have built upon his principles and created their own interpretations, such as the flying tourbillon and the multi-axis tourbillon. The sophisticated complication is arrayed with a specialised cage housing both the balance and the escapement.

Coiled around the movement or the periphery of the case, the gong spring is the indispensable part of a striking watch. The curvature reduces the thickness of the watch while also amplifying the mellifluous sound. The striking mechanism, however, comprises more than the gong spring. The gong holder, the striking mechanism barrel and the hammers all play a leading role in creating desired tonality, while the material of the mechanism as well as the case influences clarity and resonance.

Competition breeds excellence

Watchmakers continue to strive for greater precision, and with that, innovation is required. In recent years, a multitude of brands have released their own in-house movements, cross-pollinated with collaborative movements by pooling their resources and know-how, and raised the standards with ever-stringent certifications. The competition among brands and the collective development augur well for horology. As watch enthusiasts, we are in for a treat in the years to come.

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