The lengths of the links comply with the condition: A͞B=A͞C. Crank 1 of length A͞B turns about fixed axis A. Sliding link 3 turns about fixed axis C. Slider 2, moving along the axis of sliding link 3, carries rule D. When crank 1 turns about axis A, rule D envelops point H, i.e. the edge of rule D always passes through point H. At this, slider 2 has Cardan motion. The length A͞B of link 1 is varied by adjusting pivot B along slot E. The envelopes of various points lying on straight line A͞C can be obtained by adjust ing pivots B and C along slots E and G.
$1254$LG,Ge$