analytical study of connecting rods

Analytical Study of

Connecting RodsSubmitted ByFaisal Bin FarukRoll : 1205032Department of Mechanical Engineering

Supervised ByDr. Tarapada BhowmickProfessorDepartment of Mechanical Engineering

Outlines Introduction Function Types Analysis

Introduction What is a Connecting Rod ?

connecting rod or conrod connects the piston to the crank or crankshaft in a reciprocating piston engine.

What does it do ?

transmits the thrust of the piston to the crank shaft, and as the result the reciprocating motion of the piston is translated into rotational motion of the crank shaft

Introduction (Continued)

It consists of – 1. A pin – end (Small End)2. A shank section (Middle), and3. An crank end (Big End)4. Rod Cap (With nut-bolts)

Capability :-A connecting rod must be capable

of transmitting axial tension (Pull), axial compression (Push), and bending stress caused by the thrust of the piston and by centrifugal force.

Function

How does it work ?Piston in an engine is subjected to

forces generated by mass and fuel combustion.

These forces results in axial load and bending stresses in the connecting rod.

Thus the connecting rod enables crankshaft to rotate.

Types Cast Rods: Cast in sand Small little seam on both sides of the

parting edge. Used in Speed Motor. For example 3.8L

Buick engine. Cap in pin-end is fastened with bolts only. Maximum rpm 6500.

Fig : Cast Connecting rod

Types (Contd.)

Forged Rods : Thick seam on both sides (Left material) of the

parting edge left from the forging dies in forging process.

Used in speed motors like small-block Chevrolet engine.

I-beam cross section. Bolt-Nut assembly. Used in engines of rpm range about 5500-6800

or further.

Fig : Forged Connecting rod

Types (Contd.)

Forged Billet rods: Machined from a solid piece of steel. No parting edge, 100 % machined. H-beam cross section. Bolts are screwed to hold the cap on. Strongest con-rods. 1200 hp engine.

Fig : Forged Billet rod

Types (Contd.)

Sintered connecting rods: Powdered metal pressed together and then

put into an oven where it is sintered that means granuals are melted together and forms the rod.

Parting edge where cap and the rod meet is fractured.

Each cap and each rod is unique with itself. Used in engine of rpm 7000 rpm.

Fig : Sintered Connecting rod

Force Analysis

Buckling Load

According to Rankine’s Formula

For equal buckling about both axes

Force Analysis (Contd.)

We know that the force on the piston

due to pressure of gas or steam,

FL = Pressure × Area = p × A

and inertia force of reciprocating

parts, FI = Mass × Acceleration

= mR × ω2 × r ×

Net force FP = Force due to pressure of gas or steam ± Inertia force

FP = FL ± FI

Steam pressure and Inertia of reciprocating parts

Dimension Analysis

B = 4 tH = 5tarea of the section,A = 2 (4 t × t) + 3 t × t = 11 t2

Moment of inertia of the section about X-axis,

and moment of inertia of the section about Y-axis,

Application

Most commonly used in the engines of automobiles Used in all types of vehicles such as cars, trucks and bikes where combustion

engine is used Construction equipment like bulldozers, road rollers use internal combustion

engines

In modern era all kind of machines basically depends on piston, connecting rods and crank shafts. These are necessary for proper functioning of an internal combustion engine.

Thank You