cuz seals kill em
In order to work, a pendulum requires a form of energy. In a clock weights are attached to chains. As gravity pulls on the weights, the chains move the clockwork. The pendulum swings through the arc of a cycloid measuring the ratio of length, gravity, and time. When the weight on the end of the chain reaches the bottom, it stops providing energy to the clock, and the clock stops. The weights and chains must be repositioned so they can again provide energy to the pendulum. Like all machines, the clockwork eventually wears out and must be repaired or replaced.