Post on 27-Dec-2015
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Pulleys, Sprockets, and Gears
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.
Applications
SprocketsPulleys
Pulleys & Sprockets
Pulley SprocketMethod of
Transmitting Force
Belt Chain
AdvantagesQuiet, no lubrication needed, inexpensive
No slip, greater strength
Disadvantages Can slipHigher cost,
needs lubrication, noisy
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 outDriver (in)
Driven (out)
D out
D in
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.
Applications
Gears
Driven (out)Driver (in)
Driver (in) Driven (out)
Idler Gear
N = number of teeth
Gear Ratio = Input RateOutput 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 inTorque out D out N out
DriverDriven
24T36T
Example: Find gear ratio and find the input torque required so that the output torque is 100 ft-lb.
GR = N out / N in = 36/ 24 = 1.5T in = T out * N in / N out = 100 * 24 / 36 = 66.7 ft-lb
DriverDriven
12T24T
36T
Example: Find gear ratio and find the input torque required so that the output torque is 100 ft-lb.
GR = N B / N A * N C/ N B= N C / N A = 36/ 24 = 1.5T in = T out * N in / N out = 100 * 24 / 36 = 66.7 ft-lb
Gear Ratio is unchanged by the idler gear.
A BC
Compound Gear Trains
DriverDriven
15T
60T
15T
60T
GR = N B / N A * N D/ N C= 60/ 15 * 60/15 = 16
A
B
CD