22.322 Mechanical Design II

22.322 Mechanical Design II Spring 2013

Exam #1 Re-do Problem Solutions Problem 3 N2=35 N3=(2.5)(10) = 25 N4=55 N5=(7)(5)=35 N6=(9)(5)=45 +2 +2 +2

Exam #1 Re-do Problem Solutions Problem 4

Lecture 18 Balancing • 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 weight • Unbalance in rotating machines occurs when a rotating member does not possess symmetry with respect to mass • Examples: automobile tire, washing machine

Lecture 18 V2 w2R R mw2R

Lecture 18 F kx cx

Lecture 18

Lecture 18 • 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

Lecture 18 • To perform a dynamic balance of an automobile wheel, the following setup is typically used:

Lecture 18 Example

22.322 Mechanical Design II