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Valve types and arrangements
The majority of valves in use are poppet types and are fitted in either
single large or multi small arrangements.
Large single valves.
•
simple operating gear.
•
simple valve construction.
•
simple cylinder head required.
Multiple small valves.
•
Smaller valve lift required.
•
Lower inertia since components usually much lighter.
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Volumetric efficiency improved.
•
Combustion chamber design more flexible.
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Lower metal temperatures.
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Less distortion of valve lid at operating temperature.
Valve springs
Springs are required to support mass of valve in the cylinder head.
There are several spring arrangements in common use some employing single
springs while others employ multiple springs.
Single Springs
•
simplest solution.
•
vibrate at lower natural frequencies, risk of valve
bounce.
•
buckling risk for long springs.
•
large diameter springs have higher stress, bending
moment.
Series Springs
•
reduces bending stresses.
•
reduces buckling.
•
more complex.
Parallel Springs
•
reduced inertia.
•
more complex.
•
alters natural frequency and so avoids axial
vibration.
gives
safety factor in event of breakage
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