Iron Clock Movement

History

• Iron clock movements first appeared during the last half of the 14th century when clocks first incorporated visible dials and hands. These were large clocks made of iron frames and gear mechanisms. By the 17th century, Galileo -- an Italian astronomer and physicist -- and Christian Huygens -- a scientist from the Netherlands -- added pendulums to the basic clock design. Credit for the idea goes to Galileo, while Huygens incorporated the actual design into the workings of the clock. The addition of the pendulum allowed for greater accuracy in timekeeping. Current-day grandfather clock designs still include the pendulum device as part of the clock’s movement.

Cast-Iron Weights

• The pendulum inside an iron clock maintains a set back-and-forth rhythm with the help of cast-iron weights suspended alongside the pendulum’s arc, or swing. Cast-iron weights help to stabilize the clock, allowing the pendulum to swing in a natural rhythm. Cast-iron clocks situated near doors that open and close on a regular basis might lose this stabilizing effect, as vibrations offset the effects of the weights. Because of their bulky appearance, tall wooden cabinet enclosures are often used to hide these less-appealing mechanisms within the clock’s movement.

Pendulum Movements

• Pendulum movements use the force of gravity to maintain a steady swing. A pendulum consists of a long rod suspended from a fixed point. A weighted disc sits on the end, or bottom-most point of the pendulum. Gravity forces drive the downward swing, and momentum forces drive the upward swing. The longer the pendulum, the slower the clock runs, while a shorter pendulum rod produces a faster-running clock. With iron clocks, the disc device at the end of the pendulum rod includes a small nut that turns. Turning the nut one way or the other shortens or lengthens the pendulum rod. A complete turn of the nut speeds up or slows down a clock’s movement by a half-minute over a 24-hour period, according to KensingtonClock.com

Gear Mechanisms

• An iron clock design transfers the pendulum’s motion into kinetic energy and uses this energy to power its internal gear mechanisms. Iron clocks operate through weighted gear mechanisms. Weighted gears rely on the up-and-down motion of weights to wind and unwind the chains that turn the gears. As the pendulum swings, the weights move up and down. A mainspring, or spring device, enables the pendulum to maintain a continuous swing. The mainspring winds and unwinds as gravity and momentum forces move the pendulum rod back and forth. The motion or energy produced by the mainspring transfer into an escapement device that powers the gears. As the gears turn, the hour, minute and second hands on the clock move.