Design of Piston

1
Govindaraju.H.K.Assistant Professor and
Head,Department of Automobile Engg.,S J M
Institute of Technology,Chitradurga 577
502.e-mail anchith_g_raj_at_yahoo.co.inSubject
Theory and Design of Automotive Engines
Sub Code - AU51 V Semester,
Automobile Engineering
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Working of IC Engine Piston and connecting rod

connecting rod
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Definition A Connecting rod is the link
between the reciprocating piston and
rotating crank shaft
Function The function of the connecting
rod is to convert the reciprocating motion of
the piston into the rotary motion of
the crankshaft.
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
4
Nomenclature of Con Rods
Shank
Bush
Bolt and nut
Small end
Bearing (Babbitt)
Big end
Oil hole
Sectional view
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Big end details
Antifriction Babbitt
Steel Bearing Shell
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Small end details
Gudgeon pin
Bush
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Forces acting on the Connecting Rod

• The pressure on the piston inertia
• of the reciprocating parts. (Fg)
• The friction of the piston rings, (Ff )
• piston,
• piston rod.
• The longitudinal and transverse (Fm)
• component of the inertia of the rod.
• The friction of the two end bearings

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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A
B
A Bending in the plane of rotation B Bending
on the other plane
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Different cross sections
I - Section
Round and Tubular Sections
I H Sections
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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I - Section Dimensions
Ixx 4Iyy
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Materials Nickel steel Vanadium steel
Duralumin or
Other aluminum alloys
Composition 4OC8, 37Mn6, 35Mn6 MO3, 35Mn6 Mo4,
40Cr4, Mo3,40NiCr4MO2) etc.
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Forced Lubrication of con rods
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Splash Lubrication of con rods
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Drain back of oil from Oil control rings
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Manufacture of connecting rods

• Manufactured by forging process
• Surfaces are finished by broaching
• Milling of both end bosses
• Grinding on both faces
• Drilling of pin hole
• Both ends are bored and ovalised
• Bolt holes are drilled and reamed
• Cap is split off by milling
• Drilling of oil hole

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Manufacture of Big end

• Rough boring of big end in double end boring m/c
• Small end is held in v block using piston pin
• Big end is bolted on bosses between v blocks
• One end feeds rough bore
• Faces and chamfers one end of the head
• Then it with draws the other feeds on from
  opposite side reams and chamfers other end.
• Finally big end is spun with babbitt material
• Finished by broaching and burnishing process.

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
17
Manufacturing of Small end

• Drilling of small end piston clamping screw hole
  and
• Tapping of drilled hole on combined drilling and
  tapping M/C.
• Drilling of piston pin hole and reaming
• Finally slotted through the clamping screw boss
  on milling M/c.

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Bearing materials
Small end Brass or Bronze bush Provision
for lubrication
Big End White metals which are used either
tin or lead base bearing materials
(Babbitts) Composition Antimony, copper, lead
and tin Application Tin based alloys are used
for Medium speed Engines Lead based
alloy are used for High speed Engines
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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• References
• Design Data Hand Book (DDH), K. Mahadevan
• and Dr. K. Balaveera Reddy
• (B.S Publishers and Distributors)
• 2. Machine Design Exercises, S.N Trika, Khanna
  Publishers.
• 3. High Speed Combustion Engines, P.M. Heldt,
  Oxford
• and IBH Publishing Co.
• 4. Automotive Design, R.B. Gupta.
• 5. Automotive engine fundamentals F.E.PeacCock.
• T.E.Gaston Reston automotive Series Pub.

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga