How Does a Windup Grandfather Clock Work?

Winding

A windup grandfather clock needs to be wound at a regular interval, typically weekly, in order to keep accurate time. The winding is usually done with a crank that is inserted into the clock. The handle is placed into a special hole in the face of the clock and turned until the clock is fully wound. Some clocks have a chain that is pulled to serve the same purpose as winding with a crank.

Inside a grandfather clock is a series of weights. When the crank is turned, those weights are drawn up to the top of the cabinet. When fully wound, it generally takes approximately seven days for the weights to drop all the way to the bottom. The clock should be wound before the week runs out to prevent the clock from losing time. Each weight in a grandfather clock controls a different mechanism. For instance, the primary weight controls the pendulum, while another weight might control the chiming mechanism.

The key to keeping time in a grandfather clock lies in the pendulum. If a grandfather clock isn't keeping time properly, the pendulum needs to be adjusted. At the bottom of a pendulum is a nut that you must twist to adjust the small disk called the "bob." If your clock is running too fast, lowering the bob will correct the problem, while raising it will speed up a slow clock. The position of the bob affects the rate at which the pendulum swings. The face of the clock reacts to the movement of the pendulum.

In addition to keeping time, grandfather clocks are prized for their chimes. When the clock reaches the appropriate point, energy from the dropping weight triggers a hammer that strikes a rod inside the clock. To play a tune, the hammers hit the rods in a predetermined order. Different styles of clocks have different numbers of rods and hammers and produce different chimes, although the most common configuration has 12, which is the number found in clocks that play the traditional Westminster melody. This melody became famous because it is the tune played by Big Ben in London.