How a Cuckoo Clock Works

by Quinten PlummerUpdated September 12, 2017


A cuckoo clock keeps time using the swinging movement of a pendulum. A second ticks away for every back-and-forth movement of the clock's pendulum. The weight at the bottom to the pendulum is immaterial -- the movement itself is the time-keeper. In addition, the distance the pendulum moves is not critical. However, the length the of the pendulum shaft does impact time-keeping ability. The pendulum must move through its arc in one second, whether the pendulum is near or far from the clock face. The pendulum's speed never deviates through its arc. As a result, clock makers translate the time it takes a pendulum to go back and forth into second, hours and minutes on a clock.

Weights and Gears

Weights wound around the cuckoo clock's internal gears power the clock's movement. The gravitational pull of the weights descending from the clock causes the gears to turn, while the constant back-and-forth motion of the pendulum regulates the descent of the weights. The teeth on the escapement gears are precisely angled to ensure appropriate release. The release enables the pendulum movement. Furthermore, the escapement gears create the iconic tick and tock sounds associated with all pendulum clocks. As the gear's anchor engages the pendulum, the sound of the next tooth on the escapement gear falling into place makes the sound with which you are familiar.


Bellows and whistles create the characteristic "cuckoo" sound inside of the cuckoo clock. The bellows are top-heavy, with flexible, air-tight sides. When the bellows are lifted by the wires attached to the clock's gears, they are filled with air. When tension on the wire is relieved, the heavy tops of the bellows fall back into place -- causing the air inside them to rush out and into the clock's whistles. The two whistles are tuned to the notes of a cuckoo's call -- one whistle for the "cu" and the second for the "ckoo" sound.

The cuckoo bird itself is mounted on a hinged bracket. Like the clock's bellows, wires attached to the clock's gear mechanism control the cuckoo. As the wires tense and relax, the cuckoo and the cuckoo's door spring forth, and then move in and out of the door.

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