Number of Instantaneous Centres in a Mechanism:

If a mechanism contains 'n' number of links, the number of instantaneous centres or centros 'N' is provided by the following relation.

N = n (n - 1)/2 . . . (4.4)

In some of the cases the instantaneous centres are simply identifiable. Some guidelines are as:

 (1) If two links are associated through a hinged joint, the connected instantaneous centre of these two links lies at the hinge.

 (2) If the relative motion among two links is pure sliding, the associative instantaneous centre lies at infinity on a line perpendicular to the direction of sliding.

 (3) If one link contains pure rolling motion over another, the connected instantaneous centre is at the point of contact.

 (4) If a link is sliding on the curved surface of another link, the instantaneous centre is at centre of curvature of the curved surface.

 (5) If the relative motion among two links is combination of both sliding and rolling, the connected instantaneous centre lies on general normal to the contact surfaces of these links flowing through the point of contact.