Spirograph Drawing Set

A spirograph with a round guide (84 teeth inside, 108 outside), a straight guide and gears of 14, 21, 28, 42, 53 and 76 teeth, plus a triangle gear.

The patterns are hypotrochoids, and the number of points depends on the ratio of the teeth: a playful way into factors, multiples and the lowest common multiple.

Design by Printosaurus on Printables, shared under CC BY-SA 4.0. The files and photos are the designer's, unchanged.

1. Print the guides and gears; pin the guide to a board through its small holes.
2. Start with gears 53 and 76.
3. Students predict the number of points in the pattern from the tooth counts, then draw to check.