Make: Volume 91

FEATURES Art of Mathematics

turned to bicycles as a mechanism for drawing

hypotrochoid patterns like the Spirograph. “I

wanted to see if the difference in speed between

the pedals and back wheel of a bike might

produce complex shapes,” Sayers recalls.

Dismembering scrap from a local bike shop

for parts, he strove to preserve the look and

feel of a bicycle, even maintaining the saddle,

pedal, and bell. By replacing the back wheel

with a wooden drawing arm and using a pen or

(recycled) plastic bottle to hold sand or paint, he

could control the machine’s output. Sand created

temporary patterns, while chalk powder mixed

with water left beautiful ...