The lengths of the links comply with the condition: C͞D=D͞E=A͞D. Link 2 turns about fixed axis C. The end E of truss-type boom 1 slides along fixed guide a. When point E of boom 1 slides along guide a, point A of the boom travels in a straight line in the direction AC. Point B describes an arc of an ellipse. If the hoisting rope is let out while the reach of the crane is changed, hoisting hook 3 will travel horizontally.
$1649$SC,D$