I remember having a Spirograph when I was a child, unfortunately mine was second hand and didn’t have all of the bits but I still managed to create to interesting pictures with it. This one
, is slightly bigger and works on the same concept. It uses two pendulums suspended from wooden towers which are connected to drawing arms and moveable joints. A ballpoint pen is mounted at the point where the pendulums come together. The pendulums are set in motion by hand and then the motion creates a picture on the paper.