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Unformatted text preview: cap in mm. It is equal to the length of the crankpin or
big end bearing (lc), and
σ b = Allowable bending stress for the material of the cap in MPa. We know that section modulus for the cap,
bc (tc ) 2
∴ Bending stress,
bc ( t c )
bc ( t c ) 2
From this expression, the value of tc is obtained. ZC = Note: The design of connecting rod should be checked for whipping stress (i.e. bending stress due to inertia
force on the connecting rod). Example 32.3. Design a connecting rod for an I.C. engine running at 1800 r.p.m. and developing
a maximum pressure of 3.15 N/mm2. The diameter of the piston is 100 mm ; mass of the reciprocating
parts per cylinder 2.25 kg; length of connecting rod 380 mm; stroke of piston 190 mm and compression
ratio 6 : 1. Take a factor of safety of 6 for the design. Take length to diameter ratio for bearing as 1.3
and small end bearing as 2 and the corresponding bearing pressures as 10 N/mm2 and 15 N/mm2.
The density of material of the rod may be taken as 8000 kg/m3 and the allowable stress in the bolts as
60 N/mm2 and in cap as 80 N/mm2. The rod is to be of I-section for which you can choose y...
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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.
- Spring '11