Find the DOF of the following mechanisms Expain why if the D

Find the DOF of the following mechanisms. Expain why if the DOF calcuated from the mobility criterion is not consistent to the reality.

Solution

no. of links: N = 9 no. of lower pairs P₁ = 12 (at A ,B and C ,there are ternery joints. and 1 ternary joint = 2 binary joint) [ considering slider at A because picture is not vlear whether its fixed or a cylinder which can slide]

Mobility:

F = 3(N-1) - 2P1    = 3*(9-1) - 2*12 = 0

But. in actual, it has one degree of freedom, the difference is due to symmetry of the mechanism. O2B link can be neglected then N= 8 P1=10 so. F = 3*(8-1) - 2*10 =1