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How does a movement work?

One of the most beautiful aspects of horology is the way technological advances have created a movement to cater to just about every practical need. From mechanical movements through to quartz ones, via a range of different complications, this section explains how the movement inside your watch works.




The mechanical movement

Invented in the 16th century, the original mechanical movements were originally restricted to larger clocks due to their size. With advances in technology and precision, these sizes decreased to the extent a mechanical movement could fit inside a pocket watch and, eventually, the wristwatch. Containing a vast array of tiny engineered parts working in perfect synchronicity with one another, the mechanical movement is undoubtedly one of humankind’s finest achievements. But how does it actually work?

At its most simple, a movement controls the transfer of energy through a sequence of mechanical parts – from its winding stem, to its mainspring, onto its gear train – whose constant rhythm translates to a smooth sweeping motion displayed by the watch’s hands.

The energy required to start the movement is input by winding the watch’s crown – found on the side of a watch’s case, it’s an integral component in the user’s interaction with the internal mechanics of a watch. The crown is attached to a winding stem, with different ‘positions’, or gear sets, engaging specific settings such as advancing the hands or date wheel. This is also known as the ‘keyless works’.

As the user turns the crown in its winding position, the stem engages the keyless works, winding the barrel ratchet, which then coils the movement’s mainspring. Found inside a round barrel, the mainspring is a flat, coiled spring that stores the potential energy obtained from manual winding. As the spring uncoils over time, this energy is then gradually released, rotating the barrel wheel it is sat on and transferring the power into the movement’s wheels (or ‘gear train’).

(It is worth noting that it is possible to overwind a hand-wound mechanical movement. This is because the mainspring is fixed to the barrel’s wall, which allows the user to know when the watch is fully wound. When manually winding, keep going until you feel a resistance; any winding past this point can potentially snap the mainspring.)

Comprised of at least four separate wheels, the gear train is responsible for the distribution of energy from the mainspring to the hands, and when coupled with the ‘motion works’ – a term for the short train of wheels and pinions that engage the hour and minute hands – subsequently set their speed of rotation.

So thus far, we have energy; a means of storing that energy; and a way of moving the hands. But, until now, we haven’t had any way of regulating the release of said energy. This is where the escapement, pallet and balance wheel come in. In particular, the latter is a weighted wheel set on a torsion spring that allows it to oscillate at a particular frequency – think of it as the heartbeat of the watch, similar to a pendulum in a clock.

At the end of the gear train is the escapement wheel, whose outer edge is covered in a number of equally spaced angled teeth. These teeth engage the pallet, which has a fork at one end and an entry and exit jewel at the other – with the two jewels locking and releasing the escapement teeth. The fork-shaped end is positioned next to the balance wheel and impulse jewel. As the balance wheel oscillates one way and another, the impulse jewel engages the fork-shaped end of the pallet, moving it backward and forward. This repeated motion causes the entry and exit jewels at the alternate end of the pallet to lock and release the escapement wheel’s angled teeth, ensuring it rotates at a regulated frequency. The result of this loop is precise bursts of movement back to the gear train, establishing a more precise rate of timekeeping. Think of it another way: the escapement provides power to the balance wheel, which then returns it at a regulated rate.

It’s this precise number of beats, or vibrations, that advance the gear train, resulting in the movement of the watch’s hands. Different mechanical movements may have slightly different vibration rates (or frequencies) - for example, the ETA 7001 found inside the C5 Malvern 595 vibrates 21,600 times per hour, while the hand-wound version of Calibre SH21 found inside the C1 Grand Malvern Small Second vibrates 28,800 times per hour. In the latter, while its second hand may look to be moving in a fluid, sweeping motion, you are actually seeing eight individual ticks a second.

There’s no doubt about it: the mechanical movement is a technical marvel, requiring an exceptionally high level of precision to ensure timekeeping of just seconds per day (and that’s before any mention is made to further advancements like the tourbillon, which mounts the escapement and balance in a cage to negate the effects of gravity). With designs perfected using centuries’ worth of knowledge, modern mechanical movement can be thin – making them perfect for your ultra-slim dress watch – yet reliable too. While many horophiles still nostalgically refer to the mechanical movement as one of the purest forms of watchmaking, the creation of the first automatic movement in the 1920s soon opened up even more possibilities.

The automatic movement

The automatic, or self winding, movement is a more recent invention, and a profoundly practical one.

Rather than having to remember to wind your watch every day or two, as necessitated by a mechanical hand-wound movement, the automatic movement can run off the motion of your wrist thanks to an in-built rotor (we’ll discuss this in more detail later). That’s not to say it won’t stop; leave an automatic watch stationary, and its power reserve will deplete in the same manner as a hand-wound would. Wearers of automatic watches may also still choose to wind their watch using the crown, as keeping a movement near the top of its power reserve ensures the best possible accuracy. But the real benefit of an automatic watch is that, if your watch has sufficient power reserve left when you take it off overnight, the subsequent movement of your wrist should retain the level of power present when you put your watch back on in the morning. Watch winders are also useful for keeping a watch fully wound when it’s not on the wrist – it’s not unusual to hear of collectors with multiple watches keeping their automatics in winders, so they are ready to wear as soon as required!

But how do these winders keep automatic movements topped up? It’s down to the rotor weight present in any automatic movement. When a watch moves (as it would if it was sitting in a rotating watch winder, for example), the rotor spins on a set of ball bearings, transferring the kinetic energy down to the automatic device bridge. In this bridge, the energy transferred from the circular motion of the rotor weight is fed through a number of gears and ultimately down to the ratchet wheel and mainspring, which stores this as potential energy. (One significant difference between hand-wound and automatic movements is that, unlike the hand-wound, an automatic cannot be overwound. This is because an automatic movement’s mainspring features a clutch mechanism that stops excessive tension being formed.)

From this point onward, though, an automatic movement works in the same way as a hand-wound one, with energy released into the gear train, escapement and balance wheel, resulting in a smooth motion of the hands.

The quartz movement

Following the developments in the sizing and technology of microelectronics, Seiko released the world’s first commercial quartz wristwatch in 1969. Founded upon a platform of near-unrivalled accuracy at prices far below that of most mechanical watches, the shift towards quartz gathered exponential momentum throughout the 1970s. Here’s the theory behind any quartz watch.

Most simply, a battery sends electricity to a quartz crystal through an electronic circuit. The quartz crystal, which is shaped like a tiny tuning fork, oscillates at a precise frequency of exactly 32,768 times a second. The circuit counts the number of vibrations and uses them to generate regular electric pulses – one per second. These pulses drive a small stepping motor, turning gear wheels that make the watch’s second, minute, and hour hands tick.

In a sense, the analogue quartz movement isn’t so different from a mechanical one – there are still quite a lot of mechanic parts inside. Instead of a main spring in a barrel, you have a battery; instead of the balance, you have the quartz crystal. The idea of the regulation system is to provide a constant swing – or frequency – that you can count. Whether a pendulum, balance, tuning fork or quartz swing, each takes a certain amount of time. The target is to make this time as constant as possible.

The evolution of the watch was characterised by the increase of the frequency of the swing system. Early pendulum watches had a frequency of 0.5Hz, whereby each full swing would take two seconds. Watchmakers would therefore count in half-swings of one second, with the second hand on precise pendulum clocks making one step per second. Pocket watches had a frequency of 2.5Hz. With 5 steps per second, the hand would “sweep” (Christopher Ward mechanical watches mostly have a frequency of 4Hz, or eight steps per second).

With a quartz movement’s 32.768Hz frequency, there is no connection between the hand moving and the frequency anymore. Instead, the integrated circuit counts the number of steps: when it reaches 32.768 swings, a signal is sent to the motor to move the hand one step. The second hand then makes one step per second – it’s this level of precision that means quartz movements can stay accurate to a few seconds a month (or in the case of chronometer-certified quartz movements, a few seconds a year).