Trammel of Archimedes

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A Trammel of Archimedes generates the shape of an ellipse as it moves in a unique way.[1] It consists of two shuttles confined to perpendicular channels or rails, while a rod attaches to them at pivots positioned along its length. As the shuttles move back and forth, each along its channel, the end of the rod traces an elliptical path. The semi-axes a and b of the ellipse are determined by the distances between the end of the rod and the two pivots attached to it. An Ellipsograph is a Trammel of Archimedes designed to draw, cut, or machine ellipses in materials such as wood or sheet metal. Typically, an Ellipsograph has a drafting instrument attached to its rod, allowing for adjustments to the distances a and b to vary the size and shape of the ellipse being drawn. The history of such ellipsographs is unclear, but they are believed to date back to Proclus and perhaps even Archimedes himself.[2] A Trammel of Archimedes in action can be seen in animation form. Wooden versions of this mechanism have been created as toys or novelty items, sold under names like Kentucky do-nothings or nothing grinders. In these toys, the drafting instrument is replaced by a crank handle, and the position of the sliding shuttles is usually fixed.