Belts, Clutches and Brakes - Mercer...
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![Page 1: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/1.jpg)
Clutches and Brakes
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Brakes and clutches
• Clutch is a device that connects and disconnects two
collinear shafts.
– Similar to couplings
– Friction and hence heat dissipation
• Purpose of a Brake is to stop the rotation of a shaft.
• Braking action is produced by friction as a stationary part
bears on a moving part.
– Heat dissipation is a problem
– Brake fade during continuous application of braking due to heat
generated
![Page 3: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/3.jpg)
Brakes and clutches are essentially
the same devices. Each is
associated with rotation
• Brakes, absorb kinetic energy of the
moving bodies and covert it to heat
• Clutches Transmit power between
two shafts
![Page 4: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/4.jpg)
Types of Brakes
• Band
• Rim/Drum
– Internal shoe
– External shoe
• Disk
• Cone
• Many others
![Page 5: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/5.jpg)
Braking
• Forces applied
• Torque regenerated to ‘brake’
• Energy is lost :HEAT
• Temperature rise of brake materials
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Energy Considerations
• 𝑇𝑜𝑟𝑞𝑢𝑒 = 𝑇 = 𝜃 𝐼𝑒𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 = Fr
• ∆𝐾. 𝐸.=Work
• ∆𝐾. 𝐸.= 1
2𝑚 𝑣𝑓
2 − 𝑣𝑖2 + 𝐼 𝜔𝑓
2−𝜔𝑖2
𝑊𝑜𝑟𝑘 = 𝑇𝑑𝜃
• Work=MC(ΔT)-Heat loss
![Page 7: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/7.jpg)
Brake Friction Materials
• Sintered metal
– Cu +Fe+ Friction modifiers
• Cermet: sintered metal + ceramic content
• Asbestos
– (not used any more in general applications)
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Characteristics:
• High friction f=0.3 to 0.5
• Repeatable friction
• Invariant to environment conditions
• Withstand high temps
– 1500F cermet
– 1000f sintered metal
– 600-1000 asbestos
• Some Flexibility
![Page 9: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/9.jpg)
Model of Clutch/Brake
Remove relative rotation
![Page 10: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/10.jpg)
Clutches: Couple two shafts
together
![Page 11: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/11.jpg)
An Internal Expanding
Centrifugal-acting Rim Clutch
Fig. 16–3
![Page 12: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/12.jpg)
Clutch: How much force we need to
stop the relative rotation
![Page 13: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/13.jpg)
Basic Band Brake: How much force
is needed to stop the Drum rotation
![Page 14: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/14.jpg)
Alternate Band/Drum Brake
![Page 15: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/15.jpg)
Cantilever Drum Shoe Brake
![Page 16: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/16.jpg)
External Cantilever Drum Brake
![Page 17: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/17.jpg)
Common Internal Drum Brake
![Page 18: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/18.jpg)
Internal Friction Shoe Geometry
•
Fig. 16–4
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Internal Friction Shoe Geometry
Fig. 16–5
p is function of θ.
Largest pressure on the shoe is pa
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Pressure Distribution Characteristics
• Pressure distribution is
sinusoidal
• For short shoe, as in (a),
the largest pressure on the
shoe is pa at the end of the
shoe
• For long shoe, as in (b),
the largest pressure is pa
at qa = 90º
Fig. 16–6
![Page 21: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/21.jpg)
Force Analysis
Fig. 16–7
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Force Analysis
Shigley’s Mechanical Engineering
Design
Self-locking condition
MN is the Normal Moment (opens brake),
Mf is Frictional Moment ( assists closing brake)
F is actuating force
![Page 23: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/23.jpg)
Force Analysis
Shigley’s Mechanical Engineering
Design
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Force Analysis
![Page 25: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/25.jpg)
Basic Band Brake: How much force
is needed to stop the Drum rotation
![Page 26: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/26.jpg)
Notation for Band-Type Clutches and Brakes
Shigley’s Mechanical Engineering
Design Fig. 16–
13
![Page 27: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/27.jpg)
Force Analysis for Brake Band
Shigley’s Mechanical Engineering
Design
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Force Analysis for Brake Band
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Common Disk Brakes
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Geometry of Disk Friction Member
Shigley’s Mechanical Engineering
Design Fig. 16–
16
![Page 31: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/31.jpg)
Uniform Wear
Shigley’s Mechanical Engineering
Design
For uniform wear, w is constant, so PV is constant.
Setting p = P, and V = rw, the maximum pressure pa
occurs where r is minimum, r = d/2,
![Page 32: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/32.jpg)
Uniform Wear
Shigley’s Mechanical Engineering
Design
Find the total normal force by letting r vary from d/2
to D/2, and integrating,
![Page 33: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/33.jpg)
Uniform Pressure
Shigley’s Mechanical Engineering
Design
![Page 34: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/34.jpg)
Comparison of Uniform Wear with Uniform
Pressure
Shigley’s Mechanical Engineering
Design
![Page 35: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/35.jpg)
Automotive Disk Brake
Shigley’s Mechanical Engineering
Design
![Page 36: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/36.jpg)
Geometry of Contact Area of Annular-Pad Brake
Fig. 16–19
![Page 37: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/37.jpg)
Analysis of Annular-Pad Brake
Shigley’s Mechanical Engineering
Design
![Page 38: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/38.jpg)
Uniform Wear
Shigley’s Mechanical Engineering
Design
![Page 39: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/39.jpg)
Uniform Pressure
Shigley’s Mechanical Engineering
Design
![Page 40: Belts, Clutches and Brakes - Mercer Universityfaculty.mercer.edu/jenkins_he/documents/ClutchesandBrakesIntro.pdfNotation for Band-Type Clutches and Brakes Shigley’s Mechanical Engineering](https://reader034.fdocuments.us/reader034/viewer/2022051321/5add54b47f8b9aeb668cc4b1/html5/thumbnails/40.jpg)
Example 16–3
Shigley’s Mechanical Engineering
Design
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Example 16–3
Shigley’s Mechanical Engineering
Design
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Example 16–3
Shigley’s Mechanical Engineering
Design