Theory of Machine
The advantage of the piston valve over the slide valve is that in the former case

Wear is less
The pressure developed being high provides tight sealing
Power absorbed is less
Both wear and power absorbed are low

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Theory of Machine
The contact ratio is given by

(Length of the arc of contact)/(Circular pitch)
(Length of the arc of approach)/cosφ
(Length of the path of approach)/(Circular pitch)
(Length of path of recess)/(Circular pitch)

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Theory of Machine
The secondary unbalanced force due to inertia of reciprocating parts in a reciprocating engine is given by (where m = Mass of reciprocating parts, ω = Angular speed of crank, r = Radius of crank, θ = Angle of inclination of crank with the line of stroke, and n = Ratio of the length of connecting rod to radius of crank)

m.ω².r sinθ
m.ω².r cosθ
m.ω².r (cos 2θ/n)
m.ω².r (sin 2θ/n)

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