A Spirograph was a toy that was wildly popular in the 70s. It produced patterns by placing a pen inside a rolling plastic wheel and rotating it inside or around a larger stationary wheel, thus causing the pen to draw interesting things on the paper secured beneath the wheels. By switching wheels and changing the color of the pen, many beautiful designs could be produced.

Spirographs were made by Kenner Toys, going back at least as early as 1967, however similar toys were sold by various companies dating back at least to 1946. Their popularity has waned in the past 20 years, probably because of those damned Nintendos.

The exact mathematical formulae for the Spirograph is as follows:

If the radius of fixed circle is R, the radius of moving circle is r, and the offset of the pen point in the moving circle is O, then the equation of the resulting curve is defined by:

x = (R+r)*cos(t) - (r+O)*cos(((R+r)/r)*t)
y = (R+r)*sin(t) - (r+O)*sin(((R+r)/r)*t)

Information for this writeup was drawn (heh) from, of all places, eBay.

This educational toy comprised a large stationary plastic ring which was pinned to a thick corrugated cardboard sheet covered in paper. When the ring was secure, a smaller circular "wheel" chosen from a variety of sizes could be placed in the ring. This fitted into the teeth of the larger ring, a pen placed in one of the perforations in the wheel, and rotated to create an interesting pattern.

By changing the colour of the pen, (red, blue, green and black came with my set), or using a different sized wheel or positioned hole, different patterns could be created with ease.

Denys Fisher

In 1962, Denys Fisher, an engineer from Leeds, England, invented the Spirograph whilst working in his family business, King Fisher Engineering. Three years later the educational toy which was to make him fortune was finally brought to fruition.

Originally, the Spirograph was an idea for a pattern making machine for use in industry which Fisher had worked on to ensure a high degree of mathematical precision. When he hit the problem on trying to find a way to apply the invention to industry, he took his invention home much to the delight of his family who were were captivated by the colourful and intricate designs. So curious that Fisher decided to manufacture his invention as a educational toy.

Fisher set up The Denys Fisher Toys Group in 1965 with 12 employees. Its first annual turnover reached £30,000.

By 1967 Spirograph was named Toy of the Year and was bought for the American market by Kenner the same year. From 1966 to 1969 it was also named as the Best Educational Toy.

From quite early on, Fisher employed Robert Fieldhouse as his marketing and financial director to great success. The pre-tax profits from The Denys Fisher Toys Group catapulted from £70,000 in 1966 to £337,000 in 1967 due to granting product licences enabling Spirograph to be produced in America.

Denys Fisher was head of the company until General Mills, an American food company, took over in 1970.

Fisher died on 17th September 2002 at the grand age of 84 but his great invention, Spirograph lives on.

Sources
Daily Mirror 2nd October 2002
alt.gossip.celebrities

Spi"ro*graph (?), n. [L. spirare to breathe + -graph.] Physiol.

An instrument for recording the respiratory movements, as the sphygmograph does those of the pulse.