While most people are familiar with the concept of cuckoo clocks – they produce an automated cuckoo bird movement – few know how these intricately detailed timepieces actually work. After all, most cuckoo clocks don't have batteries, nor do they connect to a wall outlet. So, how exactly does a cuckoo clock?

Cuckoo Clocks: The Basics

Before we begin, it's important to note that cuckoo clocks are either mechanical or battery powered. The battery-powered models, however, are relatively new. For hundreds of years, clockmakers in Germany's Black Forest region have produced mechanical clocks, which are characterized by their automated, mechanical movement. Since then, little changed regarding cuckoo clocks with mechanical movement.

Weight-Driven Mechanics

Most genuine cuckoo clocks feature weight-driven mechanics. When shopping for a cuckoo clock, you'll probably notice pendulums hanging from the bottom. Usually designed to mimic the appearance of pine cones, these heavy pendulums are responsible for powering the clock's movement and sound.

The pendulum weights are typically made of heavy-duty cast iron. When the clock strikes the hour (or half hour in one-day timepieces), one of these pendulums  forces the wooden cuckoo bird of its enclosure and activates the bird's call. As the cuckoo bird emerges from its enclosure, hidden bellows pump air into pipes known as gedackt; thus, creating the cuckoo's call. The other pendulum is responsible for keeping time.

There are also cuckoo clocks designed with three pendulums. In addition to keeping time and producing cuckoo movement and sound, these clocks make music as well. The most common music produced by these “musical” cuckoo clocks include the traditional German Folk songs “Der fröhliche Wanderer" and "Edelweiss,” typically with 18 to 36 tones. The more tones a cuckoo clock has, the better the music.

Spring-Driven Mechanics

There are also spring-driven cuckoo clocks, which as the name suggests, are powered by springs instead of weights. Spring-driven cuckoo clocks are somewhat rare, however, with most collectors preferring the traditional weight-driven style. They typically still contain pine cone pendulums, but these weights are strictly aesthetic and serve no purpose in terms of function.

Spring-driven cuckoo clocks produce the same cuckoo bird movement and call as weight-driven clocks. However, one of the disadvantages to this style is the simple fact that springs are susceptible to failure. Over time, the clock's springs may wear down and fail, preventing the cuckoo clock from working as intended. This is why most cuckoo clocks today use weight-driven mechanics.