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Unformatted text preview: . t
∴ Total stress on the crank web,
σT = σb + σd
This total stress should be less than the permissible limits. (d) Design of shaft under the flywheel. The total bending moment at the flywheel location will
be the resultant of horizontal bending moment due to the gas load and belt pull and the vertical
bending moment due to the flywheel weight.
ds = Diameter of shaft under the flywheel.
We know that horizontal bending moment at the flywheel location due to piston gas load,
M1 = FP (a + b2) – H1 .b2 = H2 .b1 Internal Combustion Engine Parts n 1173 and horizontal bending moment at the flywheel location due to belt pull,
M2 = H1′.b2 = H2′.b1 = (T1 + T2 ) b1.b2
b ∴ Total horizontal bending moment,
MH = M1 + M2
We know that vertical bending moment due to flywheel weight,
MV = V1.b2 = V2.b1 =
∴ Resultant bending moment,
MR = ( M H )2 + ( M V )2 ...(i) We also know that π
MR = 32 ( d s ) σb
From equations (i) and (ii), the diameter of shaft (ds) may determined.
2. When the crank is at an angle of maximum twisting moment. Consider a position of the
crank at an angle of maximum twisting moment as shown...
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- Spring '11