swinging pendulum pours sand from its bob onto a variable-speed
conveyor belt which moves in a direction perpendicular to the swing
of the pendulum. The sand forms a wavy pattern on the belt which
diminishes in amplitude exponentially due to a damping mechanism
consisting of a paddle moving through thick oil. The oil reservoir
may be raised or lowered (the paddle is fixed to the pendulum) to
vary the amount of damping.