TABLE OF CONTENTS In Chapter 9, a simple kinetostatic model of a cam-follower system was presented. That model is sufficient for determining (and thus avoiding by design) the condition of gross follower jump due to inadequate spring force and/or preload. Properly designed cam-follower systems for industrial machine applications usually do not have follower jump problems, in part because they are operated at controlled speeds. Internal combustion engine valve trains, on the other hand, can experience follower jump (or toss) if the "nut behind the wheel" revs the engine beyond its redline rpm. The "redline" on the tachometer is there to indicate the maximum engine speed allowed before the cam-followers will leave contact with the cams. Modern engines with electronically controlled ignition and fuel injection are usually equipped with a rev limiter that cuts the ignition or fuel supply if the driver tries to exceed the redline rpm.
All cam-follower systems have sufficient elasticity in their components to present the possibility of residual vibrations in operation. These are oscillations of relatively small magnitude within the various links and levers that comprise the follower train. Though these oscillations are small compared to the potential deviation in follower motion that accompanies a gross jump phenomenon from over-revving, they may nevertheless create dynamic problems. In automotive valve trains, vibration of the coils of the return spring, called spring surge, is a common problem. The harmonic content of the cam profile can interact with the natural frequencies of the spring coils at particular engine speeds, causing...
