Pendulum clocks are one type of traditional, mechanical clocks. They use a weighted pendulum to set the rhythm of the clock's movement and keep it running for a period of time. Though complex, most pendulum clocks share some of the same basic parts that are essential to most clocks.
A pendulum clock is usually housed in an upright wooden case. While any kind of material works, wood is more common, since pendulum clocks are considered old-fashioned and are often used as decoration as much as for measuring time. The case must be tall enough to accommodate the length of the pendulum, and the case needs to be wide enough for the weights to hang freely as they descend. The case may also have one or more hinged glass doors to allow access to the clock's face or to the pendulum itself.
The movement is the heart of a pendulum clock, comprising all the gears and other components that keep time. One of the first decisions to make when building a clock is whether to install a complete movement or, for more intrepid builders, to create your own. Building a durable movement that keeps precise time is a difficult task that requires complex math skills and the ability to machine very finely detailed parts.
A pendulum clock's movement is based around the escapement, which is a toothed gear that engages with the pendulum and regulates the speed at which the clock runs.
The pendulum, which gives this type of clock its name, is a weight hung at the end of a wire or rod. It it attached to the escapement, which moves one step each time the pendulum swings. The weight of the pendulum will determine how fast it swings, so many pendulums have weights attached to the back to bring them into alignment with the speed of the movement.
A pendulum clock's weights are the driving force behind its operation, and also power any bells or chimes the clock may have. Traditional grandfather clocks feature three weights: one to control the timekeeping movement, one to control chimes, and one to run a moon dial or other complication. Each weight hangs from a metal cable and a pulley, which is attached to the movement.
Dial and Hands
The dial, or face, is the round or square surface of the clock with numbers and other ornaments. The dial contains several holes where owners must insert the clock's key and wind the weights, drawing them up in the case and winding their cables inside the movement.
The hands are attached to the movement through another hole in the dial. They must be light enough not to slow down the movement, and positioned to that they don't come into contact with the dial.