7
How the Crescent Clock Works
It is helpful to have an understanding of how the Crescent clock works. This insight will be
especially beneficial if troubleshooting is necessary.
The Crescent clock is driven by weight. The weight is hung from a cord that is wound
around the great wheel arbor (shaft). The weight unwinds the cord from the arbor, causing the arbor
to rotate. The gears that are attached to this arbor mesh with a train of other gears, causing them to
rotate as well. When the cord has unwound to a point where the weight has nearly reached the
floor, the clock is “wound” by winding the cord back around the arbor.
The speed at which the weight is allowed to rotate the gear train is regulated by the
pendulum. As the pendulum swings back and forth, it causes the escape lever to rock back and
forth along with the pendulum. The escape lever alternately stops and then releases one of the
wheels in the train (called the escape wheel). These contacts with the escape lever and the escape
wheel teeth generate the “tick-tock” sound of the clock.
The faster the pendulum moves back and forth, the faster the escape wheel (and the entire
gear train) will be allowed to advance. The pendulum swing period is determined by its length (or,
more precisely, the length from its pivot point to its center of gravity). Increasing the pendulum
length increases the time it takes the pendulum to complete its swing. This makes the clock run
slower. Decreasing the pendulum length decreases the time it takes the pendulum to complete its
swing, making the clock run faster. Therefore, adjusting the position of the pendulum bob along the
pendulum shaft controls whether the clock runs fast or slow and provides a means by which the
clock can be made to run “on time.”
