Belts, Clutches and Brakes
Transcript of Belts, Clutches and Brakes
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Belts, Clutches and Brakes
Belts, ropes, chains are used to convey power over a long
distance
It often used as a replacement for gears. , they are less nosy, and absorb shocks and vibration
In contrast to other system that friction is no good, here we rely on the friction to transmit power
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Brakes and clutches are essentially the same devices. Each is associated with the rotation
• Brakes, absorb kinetic energy of the moving bodies and covert it to heat
• Clutches Transmit power between two shafts
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Belts• They are four types of the belts
Size range center distance
T=0.75 to 5 mm No upper limit
d= 3to 19 mm No upper limit
A=13 to 38 mmB=8 to 23 mm Limited2β= 34o to 40o
p=2 mm and up Limited
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Belts are made from fiber reinforce urethane or rubber-impregnated
fabric reinforced with steel or Nylon
• Flat belts has to operate at higher tension than the V belt
• V belt speed should be in the range of 7000 fpm.
• V belts are slightly less efficient than flat belts, but it can transmit more power.
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Timing Belt
Timing belts transmit power at the constant angular velocity ratio, application when precise speed ratio is important
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Belt Drives, and its dimensions
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Due to friction, the tight-side tension is greater
than the slack-side tension.
rFFT )( 21
Initial tension recommended )(21
21 FFFi
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Due to friction, the tight-side tension is greater than the slack-side tension.
rFFT )( 21
r= pitch radius, from the center to the neutral axis of the belt
1F =tension on the tight side
2F =tension on the slack side Initial tension recommended
)(21
21 FFFi
Transmitted horse power
12
6300033000)( 21
dnV
TnVFFhp
T torque lb-in, n rpm, d pitch in, V fpm
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Speed ratio
1
2
2
1
rr
nn
2VgwFc
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Tension in the flat belt or round belt From the free body Diagram
sin/
2
1
2
1
02
sin)(0
02
cos2
cos)(0
fc
fc
c
cy
x
eFFFF
eFFFF
fdFF
dF
dFdFFdFdNF
dFfdNddFFF
For the V belt
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From these equation s you can evaluate tension in the belt
sin/fe
121 )( rFFT
sin/
2
1 fc eFFFF
1
11 )
1(
rT
FF c
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Maximum tension in the belt considering the effects of bending
in the belt• Fmax=KsF1
• Ks Service factor
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Belts are subjected to the fatigue loading
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Clutches
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Important issue , how much force we need to stop the rotation
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How much force is needed to stop the Drum
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