Connecting rod-presentation-1

FOURTH GROUP
PRESENTATION
Presented by
HaiNam,KienDoo,Nam,Khanh,Shain

Introduction
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 History
Evidence for the connecting rod appears in the late 3rd century Hierapolis
sawmill in Roman Asia (modern Turkey). It also appears in two 6th
century Byzantine-era saw mills excavated at Ephesus, Asia Minor (modern
Turkey) and Gerasa, Roman Syria. The crank and connecting rod mechanism of
these Roman-era watermills converted the rotary motion of the waterwheel into the
linear movement of the saw blades.
By the 16th century, evidence of cranks and connecting rods in the technological
treatises and artwork of Renaissance Europe becomes abundant; Agostino
Ramelli's The Diverse and Artifactitious Machines of 1588 alone depicts eighteen
examples, a number which rises in the Theatrum Machinarum Novum by Georg
Andreas Böckler to 45 different machines
Today, the connecting rod is best known through its use in internal combustion
piston engines, such as automobile engines. These are of a distinctly different
design from earlier forms of connecting rod used in steam engines and steam
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The difference between previous and current
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Function Of Connecting Rod
The connecting rod has two principal tasks to fulfil: it
connects the piston to the crankshaft and, since its lower
or "big" end is attached to an offset crankpin on the
crankshaft, it converts linear movement of the piston into
rotary movement of the crankshaft. By doing so, it
transforms the linear force of the piston into a rotary force
or torque.
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The connecting rod is exposed to very severe loads.
Combustion gas pressure acting downwards on the
piston exerts very heavy forces along the connecting
rod. Since the piston's speed is continually varying,
the high acceleration and deceleration forces which
result must be withstood in the form of tensile and
compressive loads on the connecting rod.
Furthermore, the oscillating movement of the con-
necting rod round the gudgeon pin axis introduces
powerful bending forces into the rod. and since the
rod is fairly long is also subject to buckling stresses.

Construction
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.
1.Rod
The rod normally has cross section of
a circle or an oval for the low and
medium-speed engines. For the high
speed engine, the rod has a section
of I shape
There is a drilled hole along the rod
to feed lubricating oil and reduce the
weight of the connecting rod
2.Small end
The small end and the rod are
normally forged in one piece
The top of the small end is drilled
hole to feed the lubricating oil for the
cooling purpose of the piston.
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3.Big end
In low –speed engines , the big end of
connecting rod normally has separate
construction and fastened with the rod by
bolts.The big end includes upper and lower
part:
The upper part is provided with a secured
pin for locating the big end and the rod.The
lower part is made with strengthening edge
to increase the rigidity.Assembling surface
between parts of the big end may be
provided with shims for adjusting oil
clearance (in case of thick wall bearing
shell).Assembling surface between upper
part and the rod may also be provided with
thin shims to adjust the height of
combustion chamber.
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For high-speed engines ,in some cases
the assembling surface between 2 parts
of big end makes with the center line of
the connecting rod an angle 30 º,45 º or
60º.It permits to reduce the cutting force
In V shape engines the two similar
connecting rods can be fitted on one
crank pin or the main connecting rod is
installed on the crank pin while the
auxiliary connecting rod is fitted on the big
end of the main connecting rod .
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V shape connecting rod

Bearing shells
Bearing shell of the small end is made
either in one piece by 2 separate halve.
Bearing shell is pressed into small end
and fixed to prevent it rotating and
moving .
Bearing shells of the big end have the
same construction with main bearing
shell . Bearing shells are tightly pressed
by 2 parts of the big end and fastened by
connecting rod bolts (or crank pin bolt).
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Construction when connecting rod connected
to piston and crank shaft
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 Materials Used Connecting rods can be made from
various grades of structural steel, aluminum, and
titanium. Steel rods are the most widely produced and
used as connecting rods. Their applications are best
used for daily drivers and endurance racing due to their
high strength and longevity .The only problem with
using steel rods is that the material is extremely heavy,
which consumes more power and adds stress to the
rotating assembly. In this work below mentioned
materials are taken as connecting rod materials and
analysis are performed. Carbon Steels, High strength
low alloy steel, Corrosion resistant high strength low
alloy steel, and Quenched and tempered alloy steel
 Carbon Steels, High strength low alloy steel, Corrosion
resistant high strength low alloy steel, and Quenched
and tempered alloy steel.
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Casting
• Cast in sand
• Small little seam on both sides of
the parting edge
• Used in Speed motor
• Cap in pin-end is fastened with bolts
only
• Maximum rpm is 6500
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Forging
• Thick seam on both
sides
• Used in speed motors
• Bolt-Nut assembly
• Used in engines of
rpm range about
5500-6800 or further
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Forged Billet rod
• Machined from a solid
piece of steel
• No parting edge
• Bolts are screwed to hold
the cap on
• Strongest con-rods, 1200
hp engine
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Sintered connecting rod
• Powdered metal pressed together and
then put into an oven where it is sintered
that means granules 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 7000rpm
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The connecting rod connects the crankshaft to the piston. It will
encounter high dynamical loads from the rapid back and forth motion.
The length of the rod is between the two centres. Bearing cups is used
for low friction rotation. An oil channel is drilled between the two
centres these channels can also have various configurations.
Initially the oil is pumped to main journal bearings ( the area where
crankshaft sits on the cylinder block ). The crankshaft has dedicated
holes , the engine oil flows through crankshaft internal bore and
reaches the big end bearing. From big end bearing it reaches
connecting rod . From connecting rod it reaches piston from piston
wall it reaches cylinders.

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Hydrodynamic non-contact bearings is used at
the connecting rod small-end and big end,
as well as in the main bearing. For these
bearings to work, a constant supply of oil
is needed. The bearings have a open track in
the centre that goes partly or all around its
circumference. At the main bearing, the oil will
enter the tracks through the supply hole
and lubricate the bearing. The rest will enter the
crankshaft leading to con-rod journal
through the channels. From here it will lubricate
and supply oil to the connecting rod.

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The “connection piece” between the piston and the crankshaft
is the connecting rod. Like all other engine parts that are
directly involved into the combustion process, the connecting
rod is highly stressed. The conrod is mainly feeded by 3
different forces:
1. the acceleration force, from the combustion process
2. the mass force, from the piston and the piston pin
3. the bending force, caused by the conrod angle
Todays modern connecting rods are divided between conrod
shaft and big end bearing housing. Additionally, an
intermediate plate allows to change the compression ratio of
the engine by different thickness of this plate. The screwed
connection of the big end bearing housing is one of the most
difficult connections for screws due to the high asymmetric
load on them. This lead into dynamic bending stresses, that
must be handled by the tightening forces. Because of this, the
tightening procedure needs extremely high attention.

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Due to the cranking of the conrod during combustion
and compression - inside the cylinder - the big end
bearing is subjected to asymmetric forces which
creates asymmetric and dynamic wear and tear.
Therefore, the ovality of the big end bearing houses
has to be checked on a regular basis. Due to the
high forces, the mating surface between the lower
half and the upper half of the big end bearing
housing need´s the highest grade of planarity, in
order to avoid fretting wear and tear.
 Measuring e.g. the diameter and ovality of a big end bearing
housing requires full tightened connecting rod bolts with
assembled connecting rod shaft.
 Require also to make use of the correct lubricant for bolts and
nuts
 Require to check the temperature of the housing

 Fixing and replacement
 Breaking phenomenon
Connecting rod is hunched and twist :Overload, manufactured
materials not guaranteed
Connecting rod is broken : overworked engine, bolt is broken, nut is
slipped off
Sliver lining shaft is corrosion : different force , lack of lubricating oil
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 Fixing method
1.clean the oil spray hole of connecting rod
2. Renew bolt and nut
3.when connecting rod is hunched and twist . We have to
renew or confine on dedicated machine
4. If Sliver lining shaft is corrosion : it has to be worn by
machine
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Connecting rod-presentation-1

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