Answer to Question #163912 in Mechanical Engineering for Arpan Chakraborty

Question

A planar closed kinematics chain ABCD is formed with rigid links AB = 2.0m, BC = 3.0m,CD = 2.5m, and DA = 2.7m with all revolute joints. Explain which of the link to be fixed to obtain a double rocker mechanism.

Answer 1

Double Rocker Mechanism is a four-bar mechanism. In this linkage, both the links pivoted to the fixed link oscillate, which is the longest, BC=3 cm.

It is a Grashof linkage for which the sum of the lengths of the shortest link, AB=2 cm, and the largest link, BC=3 cm is less than the sum of the lengths of the other two links.

$AB+BC<CD+DA \implies 2+3<2.7+2.5\implies 5<5.2$

The shortest link, AB=2 cm is the coupler. It makes a full revolution. The position of the other three links does not affect the nature of the mechanism.