ME TUMechanical Engineering DepartmentFaculty of Engineering, Thammasat University

ME311MECHANICAL DESIGN

Module 6Couplings and Keys

Dulyachot CholaseukMechanical Engineering Department

Thammasat University

ME TUMechanical Engineering DepartmentFaculty of Engineering, Thammasat University

ME311 Module 6 : Couplings and Keys 2

Contents

1. Coupling design2. Key design

ME TUMechanical Engineering DepartmentFaculty of Engineering, Thammasat University

ME311 Module 6 : Couplings and Keys 3

Coupling design1Function: connect two shafts

ME TUMechanical Engineering DepartmentFaculty of Engineering, Thammasat University

ME311 Module 6 : Couplings and Keys 4

Rigid coupling

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ME311 Module 6 : Couplings and Keys 5

Alignment problem

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ME311 Module 6 : Couplings and Keys 6

Alignment problem

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ME311 Module 6 : Couplings and Keys 7

Alignment

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ME311 Module 6 : Couplings and Keys 8

Flexible couplings

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ME311 Module 6 : Couplings and Keys 9

Universal joints for extreme misalignment

Universal joints cause speed fluctuation.

Universal joints have axial movement

ME TUMechanical Engineering DepartmentFaculty of Engineering, Thammasat University

ME311 Module 6 : Couplings and Keys 10

Universal joints Speed fluctuation

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ME311 Module 6 : Couplings and Keys 11

CV joints for extreme misalignment and sliding

Rzeppa CV Tripod CV

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ME311 Module 6 : Couplings and Keys 12

Tripod CV joints

Tripod CV

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ME311 Module 6 : Couplings and Keys 13

Rzeppa CV joints

Rzeppa CV

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ME311 Module 6 : Couplings and Keys 14

Flange couplings

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ME311 Module 6 : Couplings and Keys 15

Sizing of rigid couplings

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ME311 Module 6 : Couplings and Keys 16

Standard dimension

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ME311 Module 6 : Couplings and Keys 17

Bolt dimension

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ME311 Module 6 : Couplings and Keys 18

Calculation

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ME311 Module 6 : Couplings and Keys 19

Safety factor

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ME311 Module 6 : Couplings and Keys 20

Key design2Function: connect hub to shaft by positive contact

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ME311 Module 6 : Couplings and Keys 21

Types of keys

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ME311 Module 6 : Couplings and Keys 22

Keyway broaching

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ME311 Module 6 : Couplings and Keys 23

Keyway milling

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ME311 Module 6 : Couplings and Keys 24

Average stresses in key

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ME311 Module 6 : Couplings and Keys 25

Question

Theoretically keys should be square

(h = w) but in practice h < w for larger

shaft. Why?

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ME311 Module 6 : Couplings and Keys 26

Design procedure

Sizing the shaft and the hub

Select standard key size from the table

Determine the length from

2 s

y

N FlS h

=

If the key is longer than the standard hub

hub shaft1.2 2l d≈ −

then the use of multiple keys may be a solution.

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ME311 Module 6 : Couplings and Keys 27

Standard key size

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ME311 Module 6 : Couplings and Keys 28

Other shaft joining mechanisms

Tapered pin

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ME311 Module 6 : Couplings and Keys 29

Other shaft joining mechanisms

Spline

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ME311 Module 6 : Couplings and Keys 30

Axial positioning mechanisms

Retaining rings

Radial assembly rings

Axial assembly

rings

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ME311 Module 6 : Couplings and Keys 31

Retaining Ring Pliers