22.322 mechanical design ii

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22.322 Mechanical Design II

Spring 2013

Learning with Purpose March 20, 2013

Exam #1 Re-do Problem Solutions

Problem 3

N2=35N3=(2.5)(10) = 25N4=55N5=(7)(5)=35N6=(9)(5)=45

+2

+2

+2

Learning with Purpose March 20, 2013

Exam #1 Re-do Problem Solutions

Problem 4

Learning with Purpose March 20, 2013

Rotating parts should be designed to be inherently balanced by their geometry.An unbalance in machines is attributed to irregularities such as machining errors, size variation in bolts, nuts, welds, etc., wear and particle accumulation.To balance a shaft, disk, or gear, we need to determine the size and location of the eccentric mass.Then, to correct the problem we can make the mass distribution symmetrical by adding or removing weightUnbalance in rotating machines occurs when a rotating member does not possess symmetry with respect to massExamples: automobile tire, washing machine

Lecture 18

Balancing

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Lecture 18

w2R

mw2R

V2

R

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Lecture 18

F

kx cx

Learning with Purpose March 20, 2013

Lecture 18

Learning with Purpose March 20, 2013

For a car, tire and rim balancing is necessary from time to time.A static wheel balance entails placing the wheel in a horizontal plane suspended by a cone through its center hole.A bubble level is attached to the wheel and weights are added to the rim until the wheel sits level.This type of balancing is generally no longer done because it neglects the effect of unbalanced moments.

Lecture 18

Learning with Purpose March 20, 2013

Lecture 18

Learning with Purpose March 20, 2013

Lecture 18

Learning with Purpose March 20, 2013

Lecture 18

Learning with Purpose March 20, 2013

To perform a dynamic balance of an automobile wheel, the following setup is typically used:

Lecture 18

Learning with Purpose March 20, 2013

Lecture 18

Example