A series of experiments tracing the movement of a freely oscillating pendulum in a layer of sand.
The pendulum’s centre of gravity is slightly off-centre, meaning that the the x and y components of its movement oscillate at very slightly different frequencies; the harmonic relationship between these frequencies causes remains constant as the amplitude decreases rapidly due to friction between the pendulum and the sand. The rate of decay of the amplitude can be controlled by the depth to when the pendulum penetrates the layer of sand.
This set up is the most simple form of a harmonograph.
Copyright © 2013 Dan Dodds.