CONNECTING ROD
NILESH SINGHVIKASH KUMAR
YASHDEEP SARASWAT
INTRODUCTION
FUNCTIONS
FORCE ANALYSIS
SELECTION OF MATERIAL
DESIGN PROCEDURE
manufacturing
INTRODUCTION
The connecting rod or conrod connects the piston to the crank or crankshaft, in a reciprocating piston engine.
Converts linear motion into rotating motion
FUNCTIONS
Transmit either a push or a pull for charge(fuel+air) inlet or exhaust
Rotate the crank through both halves of a revolution, i.e. piston pushing and piston pulling
Transmits reciprocating motion into rotary
Transfers lubricant oil from crank pin to piston pin providing a splash of oil.
FORCE ANALYSIS
GAS PRESSURE Act at the time of expansion.
Force acting on piston gets transferred on small end of connecting rod.
Vital for design of cross section & eye of connecting rod.
FORCE ANALYSIS
INERTIA FORCESAct after the completion of exhaust due to vacuum generation.
Suction takes place due to these forces.
Vital for design of big end cap & bolts.
Failure of connecting rod
BUCKLING IT TAKES PLACE WHEN THERE IS A CONSIDERABLE LENGTH IN PROPORTION IT`S BREADTH.
WHIPPING STRESS the transverse component of force acting on connecting rod tries to bend the conrod in the `s` shape.
Selection of material
Medium carbon steel(carbon: .35%-.45%) for industrial engines
Alloy Steel(Nickel chromium / Chromium molybdenum) for automobile /aircraft engines.
Design procedure
Design for cross section of connecting rod
Design for big & small end bearings
Design for big end cap & bolts
Design for cross section of connecting rod
1. Consideration of buckling To make it`s strengthful both in xx
Axis & YY Axis Equally I section is preferred.
2.Dimensions of cross-section
Pressure acting on connecting rod= Area of piston x Max. pressure acting on pistonDetermination of `t` Using Rankine`s formula.Dimensions of I section
Thickness:tWidth:4tHeight:5t
Design for big & small end bearings
For small end bearing :Max. Pressure acting = Area of piston x Max. Pressure acting on piston
Pc=dp x lp x (pb)pl/d =1.5-2
For big end bearing :
Max. Pressure acting = Area of piston x Max. Pressure acting on piston
Pc=dc x lc x (pb)c
l/d =1.25-1.5
Design for big end cap & bolts
Role of inertia force acting after exhaust For For Bolts: Pi :Inertia force[refer databook] (Pi)= 2(πd.d) σt /4
For Cap: Considering the load to be avg. of Point load & U. Distributed load.
Mb= (P i) max .l 6
manufacturing
I. Drop Forging
II. Outer surfaces left Unfinished
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