The Inner Workings of Mechanical Clocks: How They Keep Time

Every time I glance at one of the vintage clocks in my collection, I am struck by the exceptional level of craftsmanship and marvel at how a mechanical device crafted over a century ago can still maintain precise timekeeping.

Mechanical clocks are machines designed to measure, keep, and indicate time. Mechanical clocks rely on a combination of essential components to operate accurately, including a power source, gear train, escapement mechanism, regulating device, and display indicator. Each component plays a critical role in maintaining the clock’s accuracy and precision in timekeeping.

For simplicity, our discussion will be limited to mechanical clocks driven by a pendulum.

Let’s examine each function in detail.


The power source of a mechanical clock comes from winding the spring or lifting the weight.

Clock weights

Energy is transferred from the winder’s hand to the mainspring or weight, which stores the energy. When the clock is running, the energy is gradually released through the gears through the escapement, causing them to turn and power the clock’s movement. This movement, in turn, powers the clock’s hands and other features, such as the striking gears. Essentially, the mechanical energy from the winding mechanism is converted and transferred through various parts of the clock to keep time.

Clean and restrained mainspring
Mainspring for an American time and strike clock


Gears, which are circular components with teeth, facilitate the transfer of energy through the gear train and turn each succeeding gear. In the case of the time-side gear train, it connects to the escape wheel, which rotates at a faster speed than the main wheel because of the interplay between the gears.

Reduction gears are commonly used in the striking or chiming mechanism of the clock, which sounds the hour or quarter-hour. The striking mechanism requires a slower and more prolonged release of energy, and reduction gears help to achieve this by slowing down the rate of rotation of the striking hammers.


In some clock designs, the gear train may also incorporate a fusee, a cone-shaped pulley with a spiral groove, which compensates for the decreasing tension of the mainspring as it unwinds. The fusee acts as a mechanical amplifier, multiplying the force of the mainspring as it unwinds and compensating for the reduction in power over time. This allows the clock to maintain accurate timekeeping even as the mainspring unwinds.

Overall, the gear train and reduction gears are essential components of a clock’s mechanism, enabling the precise transfer and conversion of energy to power its movement and features.


The escapement allows the power to “escape” at a controlled rate. The tick-tock sound heard from a mechanical clock is caused by the verge catching and releasing the teeth of the escape wheel, transmitting an impulse to the pendulum to keep it swinging.

Bushing installed on escape wheel arbour
Escape wheel and pallets


The regulator controls the speed of the clock. Pendulums with longer rods oscillate more slowly, while those with shorter rods oscillate faster.

The rate of the escapement, which controls the release of energy from the gear train, can be adjusted by altering the effective length of the pendulum, which is the oscillating component of the clock’s regulating system. This can be done by adjusting the position of the pendulum weight or changing the length of the pendulum rod. By altering the length of the pendulum, the clock can be regulated and keep more accurate time.


The clock hands provide a visual reference of the current time, while the chimes or alarms provide an audible signal at specific intervals, such as the top of the hour or the quarter hour.


Thus, the concept of synergy is essential in understanding how all the individual parts of a clock work together as a cohesive system to achieve the singular purpose of timekeeping. Each component has its specific function, but they all work together in harmony to create an accurate and reliable timekeeping tool.

The large hands of a gallery or dial clock

Mechanical clocks are a testament to the brilliance of their inventors, as many of these machines still run as well today as they did over a hundred years ago. The interaction of these five elements results in a synergy that allows these machines to do one thing: tell time.


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