A trammel of Archimedes is a mechanism that generates the shape of an ellipse. It consists of two shuttles which are confined ("trammeled") to perpendicular channels or rails and a rod which is attached to the shuttles by pivots at fixed positions along the rod.
"Bullshit Grinder" toy (ca. 1960)
Wooden ellipsograph (ca. 1900) now at Smithsonian
Ellipsograph on display at Musée d'histoire des sciences de la Ville de Genève
In mathematics, an ellipse is a plane curve surrounding two focal points, such that for all points on the curve, the sum of the two distances to the focal points is a constant. It generalizes a circle, which is the special type of ellipse in which the two focal points are the same. The elongation of an ellipse is measured by its eccentricity , a number ranging from to .
Wave pattern of a little droplet dropped into mercury in the foci of the ellipse
Image: Tilted Ellipse 2