The length of the bearings are found on the basis of

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Unformatted text preview: g pin collar thickness) 4P c Section modulus for the crankpin, π ( d )3 Z= 32 c ∴ Bending stress induced, σb = M / Z This induced bending stress should be within the permissible limits. (b) Design of bearings. The bending moment at the centre of the bearing 1 is given by M = FP (0.75 lc + t + 0.5 l1) where ...(i) lc = Length of the crankpin, t = Thickness of the crank web = 0.45 dc to 0.75 dc, and l1 = Length of the bearing = 1.5 dc to 2 dc. We also know that π 3 M = 32 (d1 ) σb From equations (i) and (ii), the diameter of the bearing 1 may be determined. ...(ii) Note : The bearing 2 is also made of the same diameter. The length of the bearings are found on the basis of allowable bearing pressures and the maximum reactions at the bearings. (c) Design of crank web. When the crank is at dead centre, the crank web is subjected to a bending moment and to a direct compressive stress. We know that bending moment on the crank web, M = FP (0.75 lc + 0.5 t) 1 × w . t2 and section modulus, Z = 6 M ∴ Bending stress, σb = Z We also know that direct compressive stress, FP σd = w...
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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.

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