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Unformatted text preview: . Assuming the screw to
be made of mild steel for which the compressive stress (σc) may be taken as 50 MPa.
dc = Core diameter of the tappet screw.
We know that load on the tappet screw (Fe), π
(d c 2 ) σ c = (d c ) 2 50 = 39.3(d c ) 2
(dc )2 = 885 / 39.3 = 22.5 or dc = 4.74 say 5 mm Ans.
and outer or nominal diameter of the screw,
d = 0.84 = 0.8 = 6.25 say 6.5 mm Ans.
We shall use 6.5 mm stud and it is provided with a lock nut. The diameter of the circular end of
the arm (D3) and its depth (t4) is taken as twice the diameter of stud.
D3 = 2 × 6.5 = 13 mm Ans.
t4 = 2 × 6.5 = 13 mm Ans.
5. Design for valve spring
First of all, let us find the total load on the valve spring.
We know that intial load on the spring,
W1 = Initial spring force (Fs) = 48 N
and load at full lift,
W2 = Full valve lift × Sitffness of spring (s)
= 16 × 8 = 128 N
...(Taking s = 8 N/mm)
∴ Total load on the spring,
W = W1 + W2 = 48 + 128 = 176 N
Now let us find the...
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- Spring '11