“Cams can produce unusual and irregular motions that would be difficult to produce otherwise. Figure 17.19a shows the basic principle of the cam. A shaft rotating at uniform speed carries an irregularly shaped disk called a cam; a reciprocating member, called the cam follower, presses a small roller against the curved surface of the cam. (The roller is held in contact with the cam by gravity or a spring.) Rotating the cam causes the follower to reciprocate with a cyclic motion according to the shape of the cam profile. Figure 17.19b shows an automobile valve cam that operates a flat-faced follower. Figure 17.19c shows a disk cam with the roller follower attached to a linkage to transmit motion to another part of the device. The following sections discuss how to draw a cam profile that will cause the follower to produce the particular motion that is needed.” (Technical Drawing with Engineering Graphics, 14th Edition by Giesecke, p. 659)

Prob. 20-24 For the setup in Fig. 20.27a, draw the displacement diagram and determine the cam profile that will give the radial roller follower this motion: up 1.50“ in 120°, dwell 60°, down in 90°, dwell 90°. Motions are to be unmodified straight line and of uniform velocity. The roller is 0.75” in diameter, and the base circle is 3.00“ in diameter. Note that the follower has zero offset. The cam rotates clockwise. (Technical Drawing, 12th by Giesecke, p. 619)

Chapter 13 Introduction to the Design Accelerator

End of Chapter 13 Problem