Drawing toys based on gears have been around since at least 1908, when The Marvelous Wondergraph was advertised in the Sears catalog. [4] [5] An article describing how to make a Wondergraph drawing machine appeared in the Boys Mechanic publication in 1913. [6]

Now define the new (relative) system of coordinates ( X ′ , Y ′ ) {\displaystyle (X',Y')} with its origin at the center of C i {\displaystyle C_{i}} and its axes parallel to X {\displaystyle X} and Y {\displaystyle Y} . Let the parameter t {\displaystyle t} be the angle by which the tangent point T {\displaystyle T} rotates on C o {\displaystyle C_{o}} , and t ′ {\displaystyle t'} be the angle by which C i {\displaystyle C_{i}} rotates (i.e. by which B {\displaystyle B} travels) in the relative system of coordinates. Because there is no slipping, the distances traveled by B {\displaystyle B} and T {\displaystyle T} along their respective circles must be the same, therefore

The other extreme case k = 1 {\displaystyle k=1} corresponds to the inner circle C i {\displaystyle C_{i}} 's radius r {\displaystyle r} matching the radius R {\displaystyle R} of the outer circle C o {\displaystyle C_{o}} , i.e. r = R {\displaystyle r=R} . In this case the trajectory is a single point. Intuitively, C i {\displaystyle C_{i}} is too large to roll inside the same-sized C o {\displaystyle C_{o}} without slipping. It is convenient to represent the equation above in terms of the radius R {\displaystyle R} of C o {\displaystyle C_{o}} and dimensionless Wheels create the magic. Toothed edges and strategically placed holes provide multiple design options with each wheel. Spirograph sets come with anywhere from six to 25 wheels with the following options.

or purse and store everything you need, though you’d need to replace the paper often. These are by far the most portable sets, but even large Spirograph sets are designed with portability in mind. They come with a carrying case in which to store wheels, pens, and paper so you can make art anywhere. Spirograph set features x c = ( R − r ) cos ⁡ t , y c = ( R − r ) sin ⁡ t . {\displaystyle {\begin{aligned}x_{c}&=(R-r)\cos t,\\y_{c}&=(R-r)\sin t.\end{aligned}}} To create designs, wheels are placed either within or along the outside of the plate or ring. Plates and rings have teeth on the outside and inside edge. Consequently, wheels can be used on either side. Plates and rings are held in place using Spiro-putty, magnets, or pins.Each Spirograph wheel has several holes into which you place a pencil or pen to create a design. Some sets have larger holes than others, and newer sets tend to have larger holes than older sets. Larger holes allow for the use of a greater variety of writing instruments. While small holes limit instrument choice, they hold the pen or pencil tighter, which can make drawing easier. Beginners often slip the gears, especially when using the holes near the edge of the larger wheels, resulting in broken or irregular lines. Experienced users may learn to move several pieces in relation to each other (say, the triangle around the ring, with a circle "climbing" from the ring onto the triangle).