State and explain in detail Grashof's law for a four-bar mechanism.

Answer 1

Grashof’s Law states that for a four-bar linkage system, if the sum of length of shortest and longest of a planar quadrilateral linkage is less than or equal to the sum of the remaining two links , then the shortest link can rotate freely with respect to neighboring link.

In a four bar chain there are four turning pairs and no sliding pairs.

Let denote the smallest link of four bar linkage with S and the longest link by L and the other two links by P and Q.

The necessary condition to satisfy Grashof’s Law is :

S + L ≤ P + Q

This condition is divided into two cases :-

1) S + L < P + Q

2) S + L = P + Q