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Chapter 17
Flexible Mechanical Elements
Lecture Slides
© 2015 by McGraw-Hill Education.  This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner.  This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part.
Chapter Outline
Shigley’s Mechanical Engineering Design
Characteristics of Some Common Belt Types
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Table 17–1
Flat-Belt Geometry – Open Belt
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Fig.17–1a
Flat-Belt Geometry – Crossed Belt
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Fig.17–1b
Reversing Belts
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Fig.17–2
Flat-belt with Out-of-plane Pulleys
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Fig.17–3
Flat-belt Shifting Without Clutch
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Fig.17–4
Variable-Speed Belt Drives
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Fig.17–5
Free Body of Infinitesimal Element of Flat Belt
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Fig.17–6
Free Body of Infinitesimal Element of Flat Belt
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Fig.17–6
Analysis of Flat Belt
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Hoop Tension Due to Centrifugal Force
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Forces and Torques on a Pulley
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Fig.17–7
Initial Tension
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Flat Belt Tensions
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Plot of Belt Tension vs. Initial Tension
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Fig.17–8
Transmitted Horsepower
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Correction Factors
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Velocity Correction Factor Cv for Leather Belts
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Fig.17–9
Pulley Correction Factor CP for Flat Belts
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Steps for Flat-Belt Analysis
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Properties of Some Flat- and Round-Belt Materials
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Properties of Some Flat- and Round-Belt Materials
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Table 17–2
Minimum Pulley Sizes for Flat and Round Urethane Belts
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Table 17–3
Crown Height and ISO Pulley Diameters for Flat Belts
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Table 17–5
Example 17–1
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Fig.17–10
Example 17–1
Shigley’s Mechanical Engineering Design
Example 17–1
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Example 17–1
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Belt-Tensioning Schemes
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Fig.17–11
Relation of Dip to Initial Tension
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Example 17–2
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Example 17–2
Shigley’s Mechanical Engineering Design
Example 17–2
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Example 17–2
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Example 17–2
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Variation of Flat-Belt Tensions at Some Cardinal Points
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Fig.17–12
Flat Metal Belts
Thin metal belts exhibit
High strength-to-weight ratio
Dimensional stability
Accurate timing
Usefulness to temperatures up to 700ºF
Good electrical and thermal conduction properties
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Tensions and Torques in Thin Flat Metal Belt
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Fig.17–13
Bending Stress in Flat Metal Belt
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Tensile Stresses in Flat Metal Belt
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Largest tensile stress during a belt pass:
Smallest tensile stress during a belt pass:
Belt Life for Stainless Steel Friction Drives
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Table 17–6
Regression Line for Stress and Passes
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Minimum Pulley Diameter
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Table 17–7
Typical Material Properties for Metal Belts
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Table 17–8
Steps for Selection of Metal Flat Belt
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Steps for Selection of Metal Flat Belt
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Example 17–3
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Example 17–3
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Standard V-Belt Sections
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Table 17–9
Inside Circumferences of Standard V-Belts
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Table 17–10
Length Conversion Dimensions
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V-Belt Pitch Length and Center-to-Center Distance
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Horsepower Ratings of Standard V-Belts
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Table 17–12
Adjusted Power
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Angle of Wrap Correction Factor
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Table 17–13
Belt-Length Correction Factor
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Table 17–14
Belting Equation for V-Belt
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Design Power for V-Belt
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Number of belts:
Suggested Service Factors for V-Belt Drives
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Table 17–15
V-Belt Tensions
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Fig.17–14
V-Belt Tensions
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Some V-Belt Parameters
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Table 17–16
V-Belt Factor of Safety
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V-Belt Tension vs. Passes
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Durability Parameters for Some V-Belt Sections
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Table 17–17
Example 17–4
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Example 17–4
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Example 17–4
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Example 17–4
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Timing Belts
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Fig.17–15
Standard Pitches of Timing Belts
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Table 17–18
Roller Chain
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Fig.17–16
Dimensions of American Standard Roller Chains
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Table 17–19
Engagement of Chain and Sprocket
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Fig.17–17
Chain Velocity
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Chordal Speed Variation
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Fig.17–18
Roller Chain Rated Horsepower Capacity
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Roller Chain Rated Horsepower Capacity
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Available Sprocket Tooth Counts
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Tooth Correction Factors K1
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Table 17–22
Multiple-Strand Factors K2
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Table 17–23
Nominal Power Ratings for Chain
From American Chain Association publication Chains for Power Transmission and Materials Handling
For single-strand chain
Nominal power, link-plate limited
Nominal power, roller-limited
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Chain Dimensions
Chain length in pitches
Center-to-center distance
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Chain Drive Power
Allowable power
Power that must be transmitted
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Variations in Tabulated Power Conditions
Power ratings in Table 17–20 are for chains of 100 pitch length and 17-tooth sprocket.
For deviations from this,
From a deviation viewpoint,
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Recommended Maximum Chain Speed
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Example 17–5
Example 17–5
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Example 17–5
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Types of Wire Rope
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Fig.17–19
Stress in Wire Rope
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Wire-Rope Data
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Table 17–24
Equivalent Bending Load
Wire rope tension giving same tensile stress as sheave bending is called equivalent bending load Fb
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Percent Strength Loss
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Fig.17–20
Minimum Factors of Safety for Wire Rope
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Table 17–25
Bearing Pressure of Wire Rope in Sheave Groove
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Maximum Allowable Bearing Pressures (in psi)
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Table 17–26
Relation Between Fatigue Life of Wire Rope and Sheave Pressure
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Fig.17–21
Fatigue of Wire Rope
Fig. 17–21does not preclude failure by fatigue or wear
It does show long life if p/Su is less than 0.001.
Substituting this ratio in Eq. (17–42),
Dividing both sides of Eq. (17–42) by Su and solving for F, gives allowable fatigue tension,
Factor of safety for fatigue is
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Factor of Safety for Static Loading
The factor of safety for static loading is
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Typical Strength of Individual Wires
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Service-Life Curve Based on Bending and Tensile Stresses
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Fig.17–22
Some Wire-Rope Properties
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Working Equations for Mine-Hoist Problem
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Working Equations for Mine-Hoist Problem
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Working Equations for Mine-Hoist Problem
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Example 17–6
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Example 17–6
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Example 17–6
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Example 17–6
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Example 17–6
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Example 17–6
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Flexible Shaft Configurations
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Fig.17–24b
Flexible Shaft Construction Details
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Fig.17–24a