Pulleys, Sprockets, and Gears

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Pulleys, Sprockets, and Gears
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Pulleys, Sprockets Gears

• Pulleys, sprockets and gears are mechanisms used
  to transfer energy through rotary motion. These
  components can be used to
• change the speed of rotation
• change the direction of rotation
• change the amount of torque available to do work
• Following is a comparison of the components and
  the equations used to calculate speed and torque.

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Applications
Sprockets
Pulleys
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Pulleys Sprockets
Pulley Sprocket
Method of Transmitting Force Belt Chain
Advantages Quiet, no lubrication needed, inexpensive No slip, greater strength
Disadvantages Can slip Higher cost, needs lubrication, noisy
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Pulleys Sprockets
Speed Ratio Input Rate
Output Rate Angular velocity uses the symbol ?
and has units of
revolutions
per minute (rpm). ? In / ? out D out / D in
Torque in D in Torque out D out
Driven (out)
D out
Driver (in)
D in
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Gears
A gear train is another mechanism for
transmitting rotary motion and torque. Gears
transmit rotary motion through interlocking
teeth. A gear train is made when two or more
gears are meshed.
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Applications
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Gears
N number of teeth
Driver (in)
Driven (out)
Driver (in)
Driven (out)
Idler Gear
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Gear Ratio Input Rate Output Rate Angular
velocity in N in Angular Velocity out N
out ? in N in ? out N out Gear Ratio ? in
N out ? out N in or Gear Ratio
? in D out ? out D in
and Torque in D in N in Torque out D
out N out
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Example Find gear ratio and find the input
torque required so that the output torque is 100
ft-lb.
Driven
Driver
24T
36T
GR N out / N in 36/ 24 1.5 T in T out N
in / N out 100 24 / 36 66.7 ft-lb
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Example Find gear ratio and find the input
torque required so that the output torque is 100
ft-lb.
A
B
C
GR N B / N A N C/ N B N C / N A 36/ 24
1.5 T in T out N in / N out 100 24 / 36
66.7 ft-lb Gear Ratio is unchanged by the idler
gear.
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Compound Gear Trains
60T
60T
Driven
Driver
C
A
D
15T
B
15T
GR N B / N A N D/ N C 60/ 15 60/15 16