(5 minutes or less)
Set up the Ellipto™ or Pendul-Art™ according to the manufacturer's instructions. If you want to build your own Drawing Board, see the information here.
(15 minutes or more)
Once the Drawing Board is adjusted, you can create wonderfully intricate designs. Try drawing one to four patterns on the same paper using pens of different colors, changing the direction and force of the push with each new color.
When the platform is displaced from its rest position, the four suspending strings exert forces on it to bring it back. You can think of these forces as acting in two directions perpendicular to each other: "north-south" and "east-west," for example. The combination of these two simultaneous motions can produce a variety of curved forms, in the same way that proper simultaneous manipulation of the two knobs on an Etch-a-Sketch™ toy allows you to draw curves.
The diminishing size of each successive repetition of the pattern is a graphic demonstration of how friction steadily dissipates the energy of a moving object.
One of our teachers put together a large-scale version of the Drawing Board that was dramatic. Rather than attempting to give detailed instructions for assembling this device, we have chosen instead to supply some labeled drawings (see below) and helpful hints. The rest is left to the dedicated experimenter.
The penholder must be counterbalanced so that the pen exerts minimum pressure on the moving board while maintaining constant contact with the writing surface.
You will have to adjust the length of the suspension ropes, since they stretch with time. Try using a knot called a slip hitch, shown in the diagram.
The placement of the weight on the board is critical. Experiment with various positions.
One person pushes the board to start rotational as well as translational motion. Another person controls the penholder, lowering the pen to start drawing and raising it to stop.
The Drawing Board should produce a pattern that repeats the same basic shape over and over again, with each cycle getting smaller. If the pattern is not consistent from one cycle to the next, try moving the weight on the board or adjusting the counterbalance weight on the penholder. Also make sure that the penholder is not shifting on the floor.
Some of the shapes you will produce with the Drawing Board are known as harmonograms or Lissajous figures. An oscilloscope can easily produce these figures, since the pattern on the scope face is generated by a single electron beam simultaneously moving vertically and horizontally on the screen. An oscilloscope can be thought of as an electronic Etch-a-Sketch™. One of our teachers had this Snack set up and running during an aftershock of the 1989 Loma Prieta earthquake. The pen traced the pattern of motion generated by the aftershock. The operating principle behind the Drawing Board - a pen directly attached to the earth with a paper only loosely attached to the earth - is the operating principle behind a seismograph.