How Should a Grandfather Clock Tick?

History

• The grandfather clock was the first clock produced in the American colonies and the first product mass-produced, according to the American Clock Gallery. Galileo Galilei developed the working theory behind the pendulum clock in 1641, but other inventors perfected the concept. The name originated in 1875 when Henry Clay Work, an American visiting England, wrote a popular song called "Grandfather's Clock" based on the story of the clock in the lobby of the George Hotel in Piercebridge. One of the brothers who owned the hotel died, and the lobby clock started losing time. When the second brother died, the clock stopped forever.

Pendulum Theory

• Although the pendulum does not directly make the grandfather clock tick by striking, the movement of the pendulum sets the clock's rhythm. The interval of a pendulum's swing depends on its length, not its weight or the distance of the swing. The interval of short pendulums varies slightly because of external forces, but long pendulums remain very accurate if not disturbed. A pendulum exactly 39.1 inches long swings once every second and provides the timing for a grandfather clock, but not the driving force. Without something to provide constant power, the pendulum would gradually come to a stop.

Weights

• Weights hanging from the windlass that forms the hub of the clock's main gear provide the constant force that keeps the pendulum swinging. The windlass weights power a grandfather clock for only slightly more than 24 hours, so owners must wind the clock every day at the same time to keep the clock running accurately. The clock key wraps the clock weight's cord around the hub of the main gear, bringing the weight to its maximum height. As the weight rotates the hub, the gear and pawl transmit the force to the end of the pendulum.

Tick Tock

• The anchor pawl at the top of the pendulum shaft makes the tick-tock noise when it strikes the teeth of the escapement gear. The pawl hooks downward on either side of the pendulum's upper end, in the shape of a ship's anchor. The pendulum swings on a bearing located slightly below the anchor pawl. As the windlass weights help swing the pendulum, one end of the pawl lets a gear tooth slip past while the other end catches a gear tooth, making a ticking noise. When the weight of the pendulum moves in the opposite direction, another tooth slips past and the other end of the pawl catches a gear, making the tock sound.