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ME 311: Dynamics of Machines and

Mechanisms

Lecture 22: Engine Dynamics: Part 4

By

Suril Shah

Mechanical Department

IIT Jodhpur

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Outline

• Pin Forces

• Balancing the Single-cylinder Engine

• Design Trade-offs And Ratios

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Simplified Kinematics

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Gas Torque

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5

Approximate Model

Approximate Model

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Inertia Force

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Shaking Force

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Inertia and

Shaking Torques

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Total torque

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Flywheel (3400 rpm)

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Pin Forces in the

Single-cylinder

Engine

• Design of the pins and the bearings at the joints

• We will calculate the effect of

– Gas force (Fg)

– Inertia force due to the piston mass (Fip)

– Inertia force due to the mass of the conrod at the wrist pin (Fiw)

– Inertia force due to the mass of the conrod at the crank pin (Fic)

– Inertia force due to the mass of the crank at the crank pin (Fir)

• Superpose them to obtain the complete pin force at each joint.

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Gas force (Fg)

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Inertia force due to the piston mass (Fip)

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Inertia force due to the mass of the conrod

at the wrist pin (Fiw)

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Inertia force due to the mass of the

conrod at the crank pin (Fic)

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Inertia force due to the mass of the

crank at the crank pin (Fir)

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19 20

800 rpm 3400 rpm

6000 rpm

Speed Vs Pin

Forces

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Pin forces in

LRCS

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Balancing Single Cylinder Engine

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Crank Over balalnced

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Exact Balance Vs Over Balance

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Effect of balancing on Pin

Forces

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THANK YOU

Next Class: Multicylinder Engine

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