Taking g 84 103 mpa or nmm2 we have 8 63 n 698 n 1 3

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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. Let dc = Core diameter of the tappet screw. We know that load on the tappet screw (Fe), π π (d c 2 ) σ c = (d c ) 2 50 = 39.3(d c ) 2 4 4 ∴ (dc )2 = 885 / 39.3 = 22.5 or dc = 4.74 say 5 mm Ans. and outer or nominal diameter of the screw, 5 dc 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. and 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 ...(Already calculated) 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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