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Unformatted text preview: e Internal Combustion Engine Parts n 1165 The thickness (t) of the crank web is given empirically as
t = 0.4 ds to 0.6 ds
= 0.22D to 0.32D
= 0.65 dc + 6.35 mm
ds = Shaft diameter in mm,
D = Bore diameter in mm, and
dc = Crankpin diameter in mm,
The width of crank web (w) is taken as
w = 1.125 dc + 12.7 mm
We know that maximum bending moment on the crank web,
t M = H1 b2 − c − 2 2 1
Z = × w. t 2
and section modulus,
t 6H1 b2 − c − 2 2 M
∴ Bending stress,
w . t2
and direct compressive stress on the crank web,
∴ Total stress on the crank web
= Bending stress + Direct stress = σb + σc
t 6 H1 b2 − c − 2 2 H
This total stress should be less than the permissible bending stress.
(c) Design of right hand crank web
The dimensions of the right hand crank web (i.e. thickness and width) are made equal to left
hand crank web from the balancing point of view.
(d) Design of shaft under the flywheel
ds = Diameter of shaft in mm.
We know that...
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- Spring '11