In the case of a circular arc cam with a flat-faced reciprocating follower, when the follower is in contact with nose of cam, the external spring force required for maintaining the contact between follower and cam is

Concept

When the flanks of the cam connecting the base circle and nose of convex circular arcs, then the cam is known as circular arc cam.

A circular arc cam with a roller follower is shown in the below figure.

When a symmetrical circular arc cam is operating a flat-faced follower, we shall consider the following two cases;

1. When the flat face has contact on the circular flank
2. When the flat face has contact on the nose

For both the contacts to be possible, the external spring force should be greater than the inertia force of the follower.

If the spring force is less than the inertia force of the follower, then while ascent and at the peak velocity point, the follower will compress the spring more and it goes a little bit high then losing the contact with the cam.

At the velocity peak point, that is where pressure angle will be equal to the angle turned by cam and the contact will be with the nose (extreme point of cam)

The weight of the follower is not considered as the follower will be in motion and the force to be considered is inertia force.