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Belt and Chain Drives
(Flexible Drive Elements)
Shigley’s Mechanical Engineering Design
Why Flexible Drives?
Shigley’s Mechanical Engineering Design
+ • Long Distances Between Shafts
• Less Expensive
• Adjustable Centers
• Tolerates some mis alignment better than gears
- • Not as compact as gears
• Some speed limits
• Power and torque limits
Common Belt Types
Shigley’s Mechanical Engineering Design
Type Pulley
1. Flat Crowned pulley
(conveyor belts)
2. Round (O-ring) Grooved pulley
3. V-belt Flanged pulleys
4. Timing (toothed) Cogged pulley
(no stretch or slip)
5. Proprietary belt designs
Characteristics of Some Common Belt Types
Shigley’s Mechanical Engineering Design
Table 17–1
Flat-Belt Geometry – Open Belt
Shigley’s Mechanical Engineering Design Fig.17–1a
Reversing Belts
Shigley’s Mechanical Engineering Design Fig.17–2
Typically
O-Ring
Drives
Flat-belt with Out-of-plane Pulleys
Shigley’s Mechanical Engineering Design Fig.17–3
Variable-Speed Belt Drives
Shigley’s Mechanical Engineering Design Fig.17–5
Free Body of Infinitesimal Element of Flat Belt
Shigley’s Mechanical Engineering Design
Fig.17–6
m is the mass/length
Free Body of Infinitesimal Element of Flat Belt
Shigley’s Mechanical Engineering Design
Fig.17–6
Analysis of Flat Belt
Shigley’s Mechanical Engineering Design
Fc = Hoop Tension Due to Centrifugal Force
Shigley’s Mechanical Engineering Design
Forces and Torques on a Pulley
Shigley’s Mechanical Engineering Design
Fig.17–7
Initial Tension
Shigley’s Mechanical Engineering Design
Flat Belt Tensions
Shigley’s Mechanical Engineering Design
Transmitted Horsepower
Shigley’s Mechanical Engineering Design
Correction Factors for Belts, Based on Manufacturer Data
Shigley’s Mechanical Engineering Design
Velocity Correction Factor Cv for Leather Belts
Shigley’s Mechanical Engineering Design
Fig.17–9
Pulley Correction Factor CP for Flat Belts
Shigley’s Mechanical Engineering Design
Belt-Tensioning Schemes
Shigley’s Mechanical Engineering Design Fig.17–11
Standard V-Belt Sections
Shigley’s Mechanical Engineering Design
Table 17–9
Inside Circumferences of Standard V-Belts
Shigley’s Mechanical Engineering Design
Table 17–10
Length Conversion Dimensions
Shigley’s Mechanical Engineering Design
V-Belt Pitch Length and Center-to-Center Distance
Shigley’s Mechanical Engineering Design
Horsepower Ratings of Standard V-Belts
Shigley’s Mechanical Engineering Design
Table 17–12
Adjusted Power
Shigley’s Mechanical Engineering Design
Angle of Wrap Correction Factor
Shigley’s Mechanical Engineering Design
Table 17–13
Belt-Length Correction Factor
Shigley’s Mechanical Engineering Design
Table 17–14
Belting Equation for V-Belt
Shigley’s Mechanical Engineering Design
Design Power for V-Belt
Shigley’s Mechanical Engineering Design
Number of belts:
V-Belt Tensions
Shigley’s Mechanical Engineering Design
Roller Chain
Shigley’s Mechanical Engineering Design
Roller Chain
Shigley’s Mechanical Engineering Design Fig.17–16
ANSI numbers
Shigley’s Mechanical Engineering Design
ANSI Chain No. XY
X: pitch in 1/8-inches
Y: 0=standard, 1=light duty,
5 for bushed chain with no rollers
Most roller chain is made from plain
carbon or alloy steel, but stainless steel is
used in food processing.
Dimensions of American Standard Roller Chains
Shigley’s Mechanical Engineering Design
Table 17–19
Engagement of Chain and Sprocket
Shigley’s Mechanical Engineering Design
Fig.17–17
Chain Velocity
Shigley’s Mechanical Engineering Design
Chordal Speed Variation
Shigley’s Mechanical Engineering Design
Fig.17–18
Roller Chain Rated Horsepower Capacity
Shigley’s Mechanical Engineering Design
Roller Chain Rated Horsepower Capacity
Shigley’s Mechanical Engineering Design
Available Sprocket Tooth Counts
Shigley’s Mechanical Engineering Design
Example 17–5
Shigley’s Mechanical Engineering Design
Example 17–5
Shigley’s Mechanical Engineering Design
Example 17–5
Shigley’s Mechanical Engineering Design
Wire Rope
Shigley’s Mechanical Engineering Design
Fig.17–19
Berg cable timing belts
Shigley’s Mechanical Engineering Design
Stress in Wire Rope
Shigley’s Mechanical Engineering Design
Wire-Rope Data
Shigley’s Mechanical Engineering Design
Table 17–24
Equivalent Bending Load
Wire rope tension giving same tensile stress as sheave bending is
called equivalent bending load Fb
Shigley’s Mechanical Engineering Design
Percent Strength Loss
Shigley’s Mechanical Engineering Design
Fig.17–20
Minimum Factors of Safety for Wire Rope
Shigley’s Mechanical Engineering Design Table 17–25
Bearing Pressure of Wire Rope in Sheave Groove
Shigley’s Mechanical Engineering Design
Maximum Allowable Bearing Pressures (in psi)
Shigley’s Mechanical Engineering Design Table 17–26
Relation Between Fatigue Life of Wire Rope and Sheave Pressure
Shigley’s Mechanical Engineering Design 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
Shigley’s Mechanical Engineering Design
Factor of Safety for Static Loading
The factor of safety for static loading is
Shigley’s Mechanical Engineering Design
Typical Strength of Individual Wires
Shigley’s Mechanical Engineering Design
Service-Life Curve Based on Bending and Tensile Stresses
Shigley’s Mechanical Engineering Design Fig.17–22
Some Wire-Rope Properties
Shigley’s Mechanical Engineering Design
Working Equations for Mine-Hoist Problem
Shigley’s Mechanical Engineering Design
Working Equations for Mine-Hoist Problem
Shigley’s Mechanical Engineering Design
Working Equations for Mine-Hoist Problem
Shigley’s Mechanical Engineering Design
Example 17–6
Shigley’s Mechanical Engineering Design Fig.17–23
Example 17–6
Shigley’s Mechanical Engineering Design
Example 17–6
Shigley’s Mechanical Engineering Design
Example 17–6
Shigley’s Mechanical Engineering Design
Flexible Shaft Configurations
Shigley’s Mechanical Engineering Design
Fig.17–24b
Flexible Shaft Construction Details
Shigley’s Mechanical Engineering Design
Fig.17–24a
