Description and Notes:
This is Model A-140 of the Fowler ellipsograph. It is in perfect working order and comes complete with the original card board box, instructions/indicator setting sheet, isometric ellipses chart, promotional advertisement brochure, and both Wrico and Leroy pen adapters. The US patent number of this device is 2,612,691, which was issued on Oct. 7, 1952. The copyright date of the instruction sheet is 1953.
The basic principle behind this ellipsograph is similar to that of the elliptic trammel, but its mechanism demonstrates an ingenious application of the single-degree-of-freedom geared five bar linkage as known in the mechanisms literature. Two large hollow gears are assembled on a plate which can be slided along the longer sides of the rectangular base frame. The stylus arm is attached to one of the gears, the position of the stylus can be adjusted along the arm to define the half length of the minor axis of the ellipse to be drawn. A small slider, which can only slide along a fixed rail perpendicularly across the frame, is attached to the center screw rod of the other gear. To define the half length of the major axis, the position of the slider relative to the edge of the gear can be adjusted along the screw by a thumb wheel. Consequently, when one rotate the stylus arm by turning its handle; the attached stylus (which can be the pencil or one of the pen points) will trace the contour of the ellipse of the specified dimensions in one revolution. According to the provided instructions, this device can draw accurate ellipses with major axis up to 7 inches long for the following three cases: 1. both major and minor axis known, 2. major axis and degree of ellipse are known, but minor axis unknown, and 3. minor axis and degree of ellipse are known, but major axis unknown.