A flat-leaf spring is used to retain an oscillating flat-faced follower in contact with a plate cam. The follower range of motion is 2 in and fixed, so the alternating component of force, bending moment, and stress is fixed, too. The spring is preloaded to adjust to various cam speeds. The preloadmust be increased to prevent follower float or jump.
For lower speeds the preload should be decreased to obtain longer life of cam and follower surfaces. The spring is a steel cantilever 32 in long, 2 in wide, and \frac{1}{4} in thick, as seen in Fig. 6–30a. The spring strengths are S_{u t}=150 kpsi , S_{y}=127 kpsi , \text { and } S_{e}= 28 kpsi fully corrected. The total cam motion is 2 in. The designer wishes to preload the spring by deflecting it 2 in for low speed and 5 in for high speed.
(a) Plot the Gerber-Langer failure lines with the load line.
(b) What are the strength factors of safety corresponding to 2 in and 5 in preload?