In 1960, self-taught engineer Denys Fisher studied the design of a one pound note. “He thought its intricate patterns were made by a simple gearing mechanism,” explains the narrator of this 1977 clip from the British television series Tomorrow’s World. “There and then, he decided to make a pattern drawing toy based on that principle.”
That toy was the Spirograph.
Winning awards in the mid-1960s and selling over 30 million units by 1977, the year this segment was filmed, the Spirograph became one of the most iconic toys of the 20th century. Watch as Fisher develops another geometric drawing device
The spirograph was the first toy of its kind, but the concept of kinematics was previously explored with mathematical models made by Scottish engineer James Watt in the late 1700s and Martin Schilling, who made over 300 models in early 1900s Germany. From the National Museum of American History:
“The Schilling models in our collection represent two mathematical topics applicable to machine design: straight line motion and curves known as trochoids…
“Trochoids are curves that are formed by a point on either the radius of a circle, the circumference of a circle, or the extension of the radius of a circle as it rolls along another curve.”
“A famous trochoid is the cycloid, which is the curve drawn by a point on the rim of wheel as it rolls along the ground, as seen in the image below or in action here. First studied by Galileo, who coined the term, cycloids are used in the shaping of arches and the design of pendulum clocks, as well as in the solution of several theoretical questions. These curves are used in the shaping of gear teeth. It was found in the late 19th century that gear teeth shaped using trochiodal edges interlocked more efficiently and reduced friction.”
Related exploration: Roulettes, Epitrochoids, and Hypotrochoids at Wolfram MathWorld, and The Mathematics of Spirograph by Katie Steckles.
Watch these related spirographish videos next:
• Two small DIY LEGO Technic spirographs
• Pangraph v4: Making Spirocakes (Spirograph Pancakes)
• The Iron Genie Harmonograph
• Eske Rex: Pendulum-Powered Drawing Machine
• Gear Shapes: Square, oval, pentagonal, organic, and more
Plus: How the differential gear works and why we need them in our cars and why do spinning rings and spinning disks have different paths?
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