Ellipsograph

Thus, if a crank centred on the crossing point of the channels is used to engage the trammel at the midway point to drive it, the rotation of the crankpin and the trammel are equal and opposite, which in practical applications results in extra friction and accelerated wear.

This is compounded by high forces owing to the short throw of the crank of only one quarter the travel of the pivots.

In these toys the drafting instrument is replaced by a crank handle, and the positions of the sliding shuttles along the rod are usually fixed.

When the rod makes an angle θ with the x-axis, the coordinates of point C are given by These are in the form of the standard parametric equations for an ellipse in canonical position.

[2] An ellipsograph is a trammel of Archimedes intended to draw, cut, or machine ellipses, e.g. in wood or other sheet materials.

The history of such ellipsographs is not certain, but they are believed to date back to Proclus and perhaps even to the time of Archimedes.