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# Forging new generations of engineers - PowerPoint PPT Presentation

Forging new generations of engineers. 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

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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.

Applications

Sprockets

Pulleys

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

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.

Gears

N = number of teeth

Driver (in)

Driven (out)

Driver (in)

Driven (out)

Idler Gear

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

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

Driven

Driver

12T

24T

36T

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.

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