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Mechanisms

Terms in this set (32)

What is a mechanism?
The part of a machine which contains 2 or more pieces arranged so that the motion of one compels the motion of others
What are mechanisms generally used for?
-Change direction of movement
-Change type of movement
-Change the speed of movement
-Change the amount of torque
When is the flow of power reversible?
If you can make the input shaft turn by turning the output shaft
What are the four types of movement?
-Rotary
-Linear
-Oscillating
-Reciprocating
Gear ratios compare the ________ to the ________
output to input
If the output gear is larger than the input gear, the speed will __________
decrease
If the output gear is smaller than the input gear, the speed will __________
increase
Force
a push or pull in a straight line
Torque
a push or pull in a circular direction
Simple gear train
-Input and Output shafts: parallel
-Flow of power: reversible
-Gear direction: opposite
Where do you find a simple gear train?
Watches, sewing machine, motor
Simple gear train with idler
-Input and Output shafts: parallel
-Speed is: constant
-Torque is: constant
-Ratio: 1:1
-Flow of power: reversible
-Input and Output gears: same direction
Where do you find a simple gear train with idler?
Paper transport rollers
Bevel Gear
-Angle: 90 degrees
-Speed: constant
-Torque: constant
-Input > Output (speed increases, torque decreases)
-Gear ratio: 1:1
-Flow of power: reversible
Where do you find a bevel gear?
Hand drill, car differential, shaft-driven bicycle
Differential Gear
-Gears used: bevel
-Axles turn: same direction
-Used in: vehicles
-Purpose: wheels spin at different speeds when turning
Worm and Wheel
-Angle: 90 degrees
-Speed is: decreased
-Torque is: increased
-Gear ratio: 24:1
-Flow of power: not reversible
-Direction of travel: reversible
Where do you find a worm and wheel?
Tuning mechanisms on string instruments, electric motors, winch
Leadscrew
-Input movement: rotary
-Output movement: linear
-Revolutions: 4.75
-Flow of power: not reversible
-Force is increased
-Direction of travel: reversible
Where do you find a leads crew?
Jack, vice
Rack and Pinion
-Input movement: rotary
-Output movement: linear
-With a larger pinion gear: the rack will move a longer distance
-Flow of power: reversible
-Direction of travel:reversible
Where do you find a rack and pinion?
Used in steering systems to convert the rotary movement of turning the steering wheel into linear motion in wheels
Universal Joint
-Angular Range: >90 degrees and <270 degrees
-Speed: constant
-Torque: constant
-Ratio: 1:1
-Flow of power: reversible
-Input and Output shafts: same direction
Where can you find a universal joint?
Drive shaft of vehicles, power take-off
Chain Drive
-Angle is: parallel
-Speed is: increased
-Torque is: decreased
-Ratio: 3:5
-Smaller drive gear: speed-decreased, torque-increased
-Shaft direction: same
Where do you find a chain drive?
Bicycle, motorcycle
Belt Drive
-Shafts: parallel
-Speed: constant
-Torque: constant
-Ratio: 1:1
-Larger drive pulley: speed-increased, torque-decreased
-Open belt: same direction
-Crossed belt: opposite
Where do you find a belt drive?
Lawn mower, car engine
Crank and Slider
-Input movement: rotary
-Output movement: reciprocating
-Slider moves: 2 in. (or diameter of crank)
-Flow of power: not reversible
Where do you find a crank and slider?
Steam train, internal combustion
Cam and Follower
-Input movement: rotary
-Output movement: reciprocating
-Flow of power: not reversible
-Direction of travel: not reversible
Where do you find a cam and follower?
Cam shaft
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