Card Set Information
Review for Mechanisms Final
When is the inverse dynamics or kinetostaics approach used?
Use to determine how much spring force is needed to keep the follower in contact with the cam at a chosen design speed.
The system spring constant
tends to be dominated by:
of the physical return spring.
The design has a large degree of control over
If the follower stiffness is in series with the return spring the effective spring constant will be dominated by:
the softest spring
Preload of a spring occurs when
the spring is compressed (or extended if an extension spring) from its
to its initial assemby length.
Why is preload important for a force-closed cam-follower?
Preloading creates residual force on the follower even when the cam is at its lowest displacement.
This helps maintain good contact between the cam and follower at all times.
Cam-Follower Design Choices
For most cam-follower systems the value of c can be estimated for a first approximation to be about 0.05 to 0.10 of the critical damping c
The spring constant and preload must be selected to guarantee a positive force at all points in the cycle.
In a force closed system the cam can
_________ on the follower.
The follower spring is responsible for
providing the force needed to keep the joint closed during the negative acceleration portions of the follower motion.
If the force F
goes negative at any time durinng the cycle what will happen to the follower and cam?
They will experience
which is where the follower and cam will part company.
The follower jump is also called the
in automotive engine valve applications.
When they meet again it will be with large and potentially damaging impact forces.
The follower jump will occur near the point of maximum negative acceleration.