Unformatted text preview: ings. Example 32.7. Design a rocker arm. and its bearings, tappet, roller and valve spring for the
exaust valve of a four stroke I.C. engine from the following data:
Diameter of the valve head = 80 mm; Lift of the valve = 25 mm; Mass of associated parts with
the valve = 0.4 kg ; Angle of action of camshaft = 110° ; R. P. M. of the crankshaft = 1500.
From the probable indicator diagram, it has been observed that the greatest back pressure
when the exhaust valve opens is 0.4 N/mm2 and the greatest suction pressure is 0.02 N/mm2 below
The rocker arm is to be of I-section and the effective length of each arm may be taken as
180 mm ; the angle between the two arms being 135°.
The motion of the valve may be assumed S.H.M., without dwell in fully open position.
Choose your own materials and suitable values for the stresses.
Draw fully dimensioned sketches of the valve gear.
Solution. Given : dv = 80 mm ; h = 25 ; or r = 25 / 2 = 12.5 mm = 0.0125 m ; m = 0.4 kg ;
α = 110°mm ; N = 1500 r.p.m. ; pc = 0.4 N/mm2 ; ps = 0.02 N/mm2 ; l = 180 mm ; θ = 135°
A rocker arm for operating the exhaust valve is shown in Fig. 32.25.
First of all, let us find the various forces actin...
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This note was uploaded on 09/30/2012 for the course MECHANICAL 403 taught by Professor A.thirumoorthy during the Spring '11 term at Anna University Chennai - Regional Office, Coimbatore.
- Spring '11