The pantograph of Heron

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The pantograph of Heron


Ιt was an impressive instrument used for copying drawings and figures (with the possibility of reduction or enlargement).

It consisted of a plane base with two toothed wheels fastened together (with the possibility of rotation around a single axle which went through their common centre) and two parallel toothed rods (that were always in contact with the toothed wheels sliding inside two grooved racks). The latter were vertically fastened on one arm rotating round the centre of the toothed wheels. Two rods (soldered vertically at the end of the two toothed rods) had, at their ends, the reading pointer and the copy writer (aligned with the centre of the toothed wheels). When the operator of the instrument followed the outline of the drawing with the reading pointer then the copy writer drew the copy in scale proportional to the ratio of the cogwheels.

SOURCES: "Heron of Alexandria, Mechanics (Arabic manuscripts Leiden MS Β and MS L)"