The Tinkertoy Construction Set is a toy construction set for children. It was created in 1914—one year after the A. C. Gilbert Company's Erector Set—by Charles H. Pajeau and Robert Pettit in Evanston, Illinois. Pajeau, a stonemason, designed the toy after seeing children play with pencils and empty spools of thread. He and Pettit set out to market a toy that would allow and inspire children to use their imaginations. At first, this did not go well, but after a year or two over a million were sold.
The cornerstone of the set is a wooden spool roughly two inches (5 cm) in diameter with holes drilled every 45 degrees around the perimeter and one through the center. Unlike the center, the perimeter holes do not go all the way through. With the differing-length sticks, the set was intended to be based on the Pythagorean progressive right triangle.
Tinkertoy sticks before 1992 were made with a diameter of 0.25 inch. The earlier sets had natural wood sticks, but changed to colored sticks in the late 1950s. From measurement, the orange sticks are 1.25 inches long; yellow, 2.15; blue, 3.35; red, 5.05; green, 7.40; and, purple, 10.85. Spools are 1.35 inches in diameter with holes of 0.30 inch depth. The ratio of succeeding stick sizes when including adjustments for spool diameter and hole depth work out to be the square root of 2, enabling the construction of 45-45-90 right triangles (see Pythagorean theorem). The theory is discussed in Pajeau's patent, no. 1113371, of 1914.
The sets were introduced to the public through displays in and around Chicago which included model Ferris wheels. Tinkertoys have been used to create surprisingly complex machines, including Danny Hillis's tic-tac-toe-playing computer (now in the collection of the Computer History Museum in Mountain View, California) and a robot at Cornell University in 1998.
Tinkertoys were inducted into the National Toy Hall of Fame at The Strong in Rochester, New York, in 1998.
Hasbro owns the Tinkertoy brand and currently produces both Tinkertoy Plastic and Tinkertoy Classic (wood) sets and parts.