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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 Sprockets Pulleys
Pulleys & Sprockets PulleySprocket Method of Transmitting Force BeltChain Advantages Quiet, no lubrication needed, inexpensive No slip, greater strength DisadvantagesCan slip Higher 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 outD out Driver (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) Driven (out) Idler Gear N = number of teeth
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 outD outN out
Driver Driven 24T 36T 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 = 1.5 T in = T out * N in / N out = 100 * 24 / 36 = 66.7 ft-lb
Driver Driven 12T 24T 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 = 1.5 T in = T out * N in / N out = 100 * 24 / 36 = 66.7 ft-lb Gear Ratio is unchanged by the idler gear. AB C
Compound Gear Trains Driver Driven 15T 60T 15T 60T GR = N B / N A * N D/ N C= 60/ 15 * 60/15 = 16 A B C D