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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