TABLE OF CONTENTS Once the s v a j functions have been defined, the next step is to size the cam. There are two major factors which affect cam size, the pressure angle and the radius of curvature. Both of these involve either the base circle radius on the cam ( R b) when using flat-faced followers, or the prime circle radius on the cam ( R p) when using roller or curved followers.
The base circle's and prime circle's centers are at the center of rotation of the cam. The base circle of a radial cam is defined as the smallest circle which can be drawn tangent to the physical cam surface as shown in Figure 7-1. All radial cams will have a base circle, regardless of the follower type used.
The prime circle is only applicable to cams with roller followers or radiused (mushroom) followers and is measured to the center of the roller follower. The prime circle is defined as the smallest circle which can be drawn tangent to the locus of the center-line of the follower as shown in Figure 7-1 for a radial cam. The locus of the centerline of the follower is called the pitch curve. Cams with roller followers are in fact defined for manufacture with respect to the pitch...
