Thank you Exploratorium for this activity: https://tinkering.exploratorium.edu/sites/default/files/Instructions/scr... and https://tinkering.exploratorium.edu/scribbling-machines
For drawing jiggly lines: (photos 1-4)
Tape some pieces of popsicle stick together, or cut a piece of glue stick. Popsicle sticks need to be taped firmly after pushing the motor shaft through them. For the glue stick, use a skewer to make a hole in it, then push it onto the shaft. Other weights can be used too, but make sure they are attached firmly. The lop-sided added weight will "offset" the motor and make it shake.
Tape the offset motor on a top edge of the plastic tub, so that when it spins the added weight does not hit the tub.
Tape the battery to the top of the tub, and attach the motor wires so that one of them is easily removable with a flap of tape (see close up photo).
Tape three marker pens as legs to the tub.
Start the motor and place the scribbling machine on the paper.
For drawing smooth circles: (photos 5-7)
Tape the motor to the plastic tub so that its shaft is pointing down, making one leg.
Tape two marker pens around the tub to make two other legs.
Tape the battery to the top of the tub, then connect it to the motor with masking tape.
Start the motor and place the circle-drawing machine on the paper. The marker pens may need to be moved around a bit until it is stable.