Figure IO-4a shows a simple plate or disk cam driving a spring loaded, roller follower.
This is a force-closed system which depends on the spring force to keep the cam and
follower in contact at all times. Figure 1O-4b shows a lumped parameter model of this
system in which all the mass which moves with the follower train is lumped together as
m, all the springiness in the system is lumped within the spring constant k, and all the
damping or resistance to movement is lumped together as a damper with coefficient c.
The sources of mass which contribute to m are fairly obvious. The mass of the follower
stem, the roller, its pivot pin, and any other hardware attached to the moving assembly all
add together to create m. Figure 1O-4c shows the free-body diagram of the system acted
upon by the cam force Fe, the spring force Fs, and the damping force Fd. There will of
course also be the effects of mass times acceleration on the system.