The lengths of the links comply with the condition: A͞B=B͞C=B͞D. When link 5 moves along the fixed guides its point D travels along straight line Ad. Point C of link 2 travels along straight line AC. Any other point of link 2 lying on circle f of radius B͞A, for example point E, also, like point C, moves along a straight line passing through point A (line Am for point E). The motion of link 2 can also be produced by the rolling of circle f, rigidly secured to link 2, without slipping around fixed circle g, the radii of the circles being in the proportion A͞B:D͞C.
$1535$SC,GI$