How Does a Cuckoo Clock Work?
There are several types of cuckoo clocks. The least expensive is the non-musical one-day clock, which requires winding once a day. The weights hang by chains, and descend as the clock "unwinds." To wind it, pull the end of the chain to bring the weights back up and keep the pendulum swinging. The pendulum drives the mechanical gears of the brass movement inside the clock, which in turn drives the hands on the face. Each tick of the pendulum advances the hands a fraction of the circumference of the clock face and drops the weight a tiny bit.
Eight-day clocks work exactly like one-day clocks, except the weights are heavier and the clock needs to be wound only once every eight days.
Musical cuckoo clocks have two movements instead of just the one regulating time. The third weight drives the second movement, which produces a series of notes when the clock strikes. Usually the melodies played are different for the hour and the half-hour, the most popular being "Edelweiss" and "The Happy Wanderer." The musical movement is like those found in music boxes: a metal drum with small pins set at intervals to produce the proper notes as the drum turns and the pins strike a steel comb.
Modern quartz clocks run on batteries instead of weights and use a recorded cuckoo sound. The "weights" are usually plastic and ornamental. Quartz clocks usually run for about a year, the life of the battery, and many come with a photo-sensor that shuts the cuckoo off at night. These clocks are not considered as authentic as "real" carved wooden cuckoo clocks with gears and weights.