The Single Cylinder Engine

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The Single CylinderEngine

A presentation by

Chris Kopchick

Matt RoonJohn Gesek

11/21/2005ME 358


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ABSTRACT

We are to design a slider crank mechanism consisting of a crankshaft,connecting rod, and piston. The requirements for piston travel must not

exceed 0.06m due to strict cubic inch tolerances. Within the cylinder or

ground the velocity of the piston must not exceed 2 m/s with a constant

crankshaft angular velocity of 600 rpm during the velocity analysis due to a

weakness in the casting of the engine block. This particular engine will be

operating at a constant velocity, however if we were to apply an angularacceleration of 10 radians/second to the crankshaft, we must not exceed a

piston acceleration of 20 m/s^2. This requirement will satisfy the side load

tolerances on the ring lands. Our two main points of interest will be at TDC

(Top Dead Center) and BDC (Bottom Dead Center) for piston travel and 45

degrees for piston velocity and acceleration. This slider crank assembly will

be a Grashof mechanism with a DOF=1. With an operational constant idleof 600 rpm we designed a short stroke, long rod combination resulting in

less torque. This setup will also provide extended bearing life and promote

exceptional ring seal.


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INTRODUCTION

In this application we are using a Grashof slider crankmechanism better known specifically as a single

cylinder engine. This internal combustion engine will be

used in a constant idle application such as a household

generator. Simply put, a force is exerted on the pistonduring the combustion process (a combination of fuel,

air, and spark). This forces the piston downward, which

through rotation of the connecting rod, causes the

crankshaft to rotate. This rotation is the output of the

mechanism and is widely used to power lawnmowers,

snow blowers, generators, etc.


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ENGINE ASSEMBLY

ConnectingRod


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2-D DRAWING OF THE ENGINE


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CRITICAL PARAMETERS

Applying to TDC, BDC:1) Piston travel must not exceed 0.06m due to cubic inch

requirements

Applying to 45 degrees2) Piston velocity must not exceed 2 m/s at a constant

crankshaft angular velocity of 600 rpm due to a

weakness in the casting of the engine block

3) Piston acceleration must not exceed 20 m/s^2, with an

initial angular crankshaft acceleration of 10 rad/sec,

due to side load requirements on the piston ring lands.


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Results If Critical Parameters Are Exceeded


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DEGREES OF FREEDOM

Grueblers Equation#DOF = 3L-2J1-J2-3G

L = 4

J1 = 4

J2 = 0

G = 1

#DOF = (3*4)-(2*4)-0-(3*1) = 1 DOF


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POSITION ANALYSIS TDC and BDC

TDC Initial Conditions2 = 0

A = 0.029m

B = 0.19113m

C = 0m

TDC Calculations3 = 180

D = 0.22013m

BDC Initial Conditions2 = 180

A = 0.029m

B = 0.19113m

C = 0m

BDC Calculations3 = 180

D = 0.16213m


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POSITION ANALYSIS 45 degrees

Initial Conditions2 = 45

A = 0.029m

B = 0.19113m

C = 0m

Calculations3 = 173.84

D = 0.210553m


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VELOCITY ANALYSIS TDC and BDC


3 = 180

A = 0.029m

B = 0.19113m

C = 0mD = 0.16213m

BDC Calculations3 = 9.53343 rad/sec

d/dt = 0 m/s

TDC Initial Conditions2 = 0

3 = 180

A = 0.029m

B = 0.19113m

C = 0mD = 0.22013m

TDC Calculations3 = -9.53343 rad/sec

d/dt = 0 m/s


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VELOCITY ANALYSIS 45 degrees


3 = 173.84

A = 0.029m

B = 0.19113mC = 0m

D = 0.210533m

Calculations3 = -6.7803 rad/secd/dt = -1.4275 m/s


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ACCELERATION ANALYSISTDC and BDC


3 = 180

A = 0.029m

B = 0.19113m

C = 0mD = 0.16213m

3 = 9.53343 rad/sec

d/dt = 0 m/s

BDC Calculations3 = 1.51729 rad/sec^2

d^2/dt^2 = 0 m/s^2


3 = 180

A = 0.029m

B = 0.19113m

C = 0mD = 0.22013m

3 = -9.53343 rad/sec

d/dt = 0 m/s

BDC Calculations3 = -1.51729 rad/sec^2

d^2/dt^2 = 0 m/s^2


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ACCELERATION ANALYSIS45 degrees


3 = 173.84

A = 0.029m

B = 0.19113mC = 0m

D = 0.210533m

3 = -6.7803 rad/sec

d/dt = -1.4275 m/s

Calculations3 = -14.7957 rad/sec^2

d^2/dt^2 = -11.295 m/s^2


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Working Model Animation

Animation of Single Cylinder Engine
http://e/ME%20358/Semester%20Project/Model_1.dathttp://e/ME%20358/Semester%20Project/Model_1.dathttp://e/ME%20358/Semester%20Project/Model_1.dathttp://e/ME%20358/Semester%20Project/Model_1.dathttp://e/ME%20358/Semester%20Project/Model_1.dathttp://e/ME%20358/Semester%20Project/Model_1.dat


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RESULTS

When analyzing TDC and BDC, our design satisfiesall critical parameters. Our piston travel was calculatedout to be 0.22013-0.16213=0.058m. This is within our0.06m travel and displacement tolerances.

When analyzing the initial 45 degree condition, we

calculated our piston velocity to be 1.4275 m/sdownward and piston acceleration of 11.295 m/s^2downward. With our present initial conditions, thisminimizes the chance of engine block fracture due to aweakness in the casting, and satisfies our piston side

load requirements on the ring lands.Analyzing the graphs in Working Model, Our

position, velocity, and acceleration results coincide verynicely with our calculated results.


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CONCLUSIONS

We can see that one of the main problems with this type ofmechanism is controlling velocity and acceleration of the piston.

For a given displacement, the piston speed and acceleration can be

lowered by increasing the bore and decreasing the stroke. This

reduces stresses on the block, connecting rod, and crankshaft.

Also, increasing the length of the connecting rod would yield aslightly different piston position curve with flatter plateaus. This

would also reduce stresses on the crankshaft and block.

An improvement to the techniques used in analyzing this

mechanism might involve building a mock-up of the engine and

measuring deformations and heat produced in the bearings. Thiswould give much insight about the critical parameters of the engine.


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Resources Used

Working Model (Slider Crank) Solid Works 3D 2005

Design of Machinery, Robert L. Norton

The Single Cylinder Engine

Documents

Transcript of The Single Cylinder Engine