Harmonograph. A Victorian drawing machine: two pendulums swing at right angles and move a pen over the paper, while a third one rocks the table. When their frequencies stand in simple ratios such as 2 : 3 the pen closes a figure; a tiny mistuning makes the figure turn slowly on itself, and friction shrinks it towards the centre. Nobody draws these curves: the pendulums do. Grab the pen and swing it: drag, and let go · click for a new drawing.
Harmonograph
A Victorian drawing machine: the pendulums draw, not the hand.
How it works
How it works. Two pendulums swing at right angles and move a pen across the paper, while a third gently rocks the table. When their frequencies stand in simple ratios such as 2 : 3 the pen closes a figure; a small mistuning makes the figure turn slowly on itself, and friction shrinks it towards the centre.
Lissajous figures. Jules Antoine Lissajous studied these curves in 1857 with mirrors fixed to vibrating tuning forks. Victorian drawing rooms turned them into a pastime with machines like this one.
Draw with it. Grab the pen and swing it: when you let go, the pendulums carry on from your gesture. Turn the mandala on to repeat the drawing around the centre, and keep earlier drawings to build up layers.