The Badger wrote: ↑Tue Aug 28, 2018 12:32 pm
Camking, how are the limitations of the amount of dwell on your cams figured? Is it the limits of the profile, limits of valve spring paired with valve weight? Or something completely different?
The maximum valve acceleration does not occur over the nose of the cam. It occurs much earlier when the valve spring force has not reached its peak. Not even close.
Which is why the valve is launched free of the cam while the valve is still on the opening slope.
If we increase valve spring seat force to control valve float, the spring force over the nose becomes excessive.
Since (once again) F = M * A, the spring
Force required is determined by the
Mass of the valve train (valve assembly, push rod, lifter, etc) and the
Acceleration determined by the cam lobe and rpm.
The optimum solution requires very light components with high strength; its called valve train stiffness.
The cam plays an important role since it determines the valve acceleration. An improperly designed cam lobe, even with necessary lift and duration, can produce problems of valve train instability at certain engine speeds and even self destruction.
This is due to resulting vibrations which can produce amplified harmonics; wear, float, bounce. and piston dome impact.