slider Crank mechanism term Project Report

7/31/2019 slider Crank mechanism term Project Report

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

PRROJECT REPORT:

SLIDER CRANK MECHANISM.

GROUP MEMBERS:

1.SYED ANIS BADSHAH ME-001

2. SHAFIQUE AHMAD ME-032

3. SAYED SHAHID RAZA ME-034

4. SYED IBRAHIM HASSAN ME-035

5. SANAUALLAH KHATTAK ME-044

SUBMITTED TO:

ENGR; MUAZAMA ARSHAD

7/31/2019 slider Crank mechanism term Project Report

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

OUTLINE: Introduction and Working of crank mechanism.

Working principle of crank mechanism

Terminology and kinematics of crank mechanism.

Types of crank mechanism.

Applications and uses.

Failure in crank.

Design consideration.

Conclusion.

Crank mechanism:

Mechanism in which rotary motion of crank is converted

into the linear motion of the piston or any other integral

element.

o Crank is the main element used in crank mechanism.

Aslidercrank (see illustration) is most widely used to

convert reciprocating to rotary motion (as in an engine) or

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

to convert rotary to reciprocating motion (as in pumps),

but it has numerous other applications.

Parts of crank mechanism:

I.Gide frame.

II.Slider

III.Wrist pin

IV.Connecting rod

V.Crank pin

VI.Crank

VII.Crank shaft

Principal parts of slider-crank mechanism

Positions at which slider motion reverses are called dead

centers. When crank and connecting rod are extended in a

straight line and the slider is at its maximum distance from

the axis of the crankshaft, the position is top dead center

(TDC); when the slider is at its minimum distance from the

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

axis of the crankshaft, the position is bottom dead center

(BDC).

The conventional internal combustion engine employs a pistonarrangement in which the piston becomes the slider of the slider-

crank mechanism.

Radial engines for aircraft employ a single master connecting rodto reduce the length of the crankshaft. The master rod, which is

connected to the wrist pin in a piston, is part of a conventionalslider-crank mechanism. The other pistons are joined by their

connecting rods to pins on the master connecting rod.

Principle of crank mechanism.To convert rotary motion into reciprocating motion, the slider crank is part

of a wide range of machines, typically pumps and compressors. Another

use of the slider crank is in toggle mechanisms, also called knuckle joints.

The driving force is applied at the crankpinso that, at TDC, a much larger

force is developed at the slider.

Terminology used in crank mechanism:

Terminology used in crank mechanism is;

1. Linkage

2. Crank angle3. Connecting rod4. Crank shaft geometry and kinematics.

1)- linkage: A set of rigid bodies, called links, joined together at pivots by

means of pins or equivalent devices.

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

Linkages are used to transmit power and information. They maybe employed to make a point on the linkage follow a prescribed

curve, regardless of the input motions to the linkage. They are also used to produce angular or linear displacement. If the links are bars the linkage is termed a bar linkage. A commonly occurring variation of the four-bar linkage is the

linkage used in reciprocating engines (see illustration).

Slider Cis the piston in a cylinder, link 3 is the connecting rod,and link 4 is the crank. (Link 1 is the fixed base, A and D are

pivots, R is the length of the crank, L is the length of theconnecting rod, and denotes the angle of the crank.)

This mechanism transforms a linear into a circular motion, orvice versa.

The straight slider in line with the crank center is equivalent to apivot at the end of an infinitely long link.

2)- crank angle:The angle between a crank and some reference direction. Specifically, the

angle between the crank of a slider crank mechanism and a line from

crankshaft to the piston.

3)- connecting rod:

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

A rod that transmits motion or power from one moving part to another,

especially the rod connecting the crankshaft of a motor vehicle to a

piston. Also called pitman.

4)-crank geometry and kinematics:Definitions

l= rod length (distance between piston pin and crank pin)r = crank radius (distance between crank pin and crank center, i.e. half

stroke)

A = crank angle (from cylinder bore centerline at TDC)

x= piston pin position (upward from crank center along cylinder bore

centerline)

v = piston pin velocity (upward from crank center along cylinder bore

centerline)

a = piston pin acceleration (upward from crank center along cylinder bore

centerline) = crank angular velocity in rad/s

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

Diagram showing geometric layout of piston pin, crank pin and crank center

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

Types of crank mechanism:

1)- CRANK AND LEVER MECHANISM. 2)-DOUBLE CRANK MECHANISM. 3)-SINGLE SLIDER CRANK CHAIN MECHANISM. 4)- MULTIPLE SLIDER CRANK MECHANISM.

1)- CRANK AND LEVER MECHANISM. This mechanism is basically used in BEAM ENGINE.

This mechanism consists of four links as shown.

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

In this mechanism when the crank rotates about the fixed

center, the lever oscillates about a fixed center. The end of the

lever is connected to a piston rod which reciprocates due to the

rotation of the crank.

2)- double CRANK MECHANISM. This mechanism is used for a coupling rod of a locomotive.

In this mechanism the links having equal lengths act as crank

and are connected to the respective wheels.

One link act as a coupling rod and the other link is fixed inorder to maintain a constant center distance between them.

The main purpose of this mechanism is to transmit rotarymotion from one wheel to the other wheel.

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

3) -single slidED crank CHAIN mechanism.

This mechanism consist of one sliding pair , and three turning pairs. Usually found in reciprocating steam engine. Its main purpose is to converts rotary motion into reciprocating

motion and vice versa.

4)-multiple slider crank mechanism. It consist of more than one sliding pair.

Usually found in Gnome rotary engine.

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

Applications and uses.

Used in in diesel engines.Used in petrol engines.Used in rotary engines.Used in beam enginesUsed for coupling rod of locomotivesUsed in steam engine.Used in toggle mechanism i.e. knuckle joints.Used in bull engine.Used in shaping and slotting machines.

Used in Oldhams coupling.Used in quick return mechanism.Used in spring mechanism to store energy.Used in pedals of bicycles.Used in bucket pulley system in well.

Failure in crank mechanism:1. Fracture initiated in a segregated region near the neutral bending axis of pin

and produced a woody fracture plane perpendicular to the direction ofimposed piston loading. This woody fracture existed prior to machining and

induction hardening. The woody fracture location, orientation, and size are

similar in both crankshafts.

2.The large woody fracture region was produced by stresses that acted in a cross

planar direction as evidenced by the orientation of secondary cracking.

3.The woody fracture pre-existed final machining and heat treatment, as

evidenced by the disruption of tool withdrawal markings in the oil hole oncrank. (A similar determination was not possible on crank because the

material containing the oil hole and woody fracture intersection was not

available.)

4. Regions of segregated material, including MnS inclusions and higher carbon,

tempered marten site bands,

Existed throughout the crankshaft with some segregated areas extending to or

near the journal surface.

5. Cracking continued from the edges of the woody fracture plane through the

hardened case to the journal surface in service by low cycle fatigue.

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DEPARTMENT; MECHANICAL ENGG;

6. Fatigue propagation was by combined bending and torsional stresses. The

actual level of these stresses as Compared to design or expected stress levels

in this engine is unknown.

7. When the fracture reached the bearing interface, spilling and localized seizure

caused bearing failure and engine outage. Lubrication conditions appearednominal as evidenced by bearing, piston, and oil Examination.

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

Design consideration: Diameter of crank= 3 inch

Length of connecting rod= 6 inch

Length of piston = 2.5 inch

Bed ways length= 10 inch

Bearing for bed ways= small 10 ball bearings.

Operations performed:Following operations are done on the construction of this project i.e.

Slider cranks mechanism.

Drilling.

Lathe machines operations(facing, turning, cutting)

Rough turning.

Finishing.

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;

Conclusion: We conclude that crank mechanism is much important in all

types of engines especially in ic engines, and reciprocating

engines.

Proper design is carried out rather failure will occur

Material is used according to the kind of load. For high duty

high carbon steel is used and for low duty cast iron is used.

Proper adjustment is carried to between the piston and

cylinder side wall in order to avoid striking, and for long life of

machine.

Size of crank is taken according to the desired rpm, and size of

connecting rod is taken according to the crank.

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4RD SEMESTER, MECHANICAL

DEPARTMENT; MECHANICAL ENGG;