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Mechanisms (Rotary motion mechanisms (Friction drives (Friction drives are…
Mechanisms
Rotary motion mechanisms
Theese are mechanisms that transmit effort and motion in a circular way, from the input to the output.
Friction drives
Friction drives are made up of two or more wheels that are in contact. The first wheel is called primary drive wheel an the second one is the output wheel. When the primary drive wheel moves it turns the output wheel and starts moving. The ratio between the rotation velocity of the wheels or pulleys depends on the relative size of the wheels. It is expressed by thi equation : N
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Pulleys with belt
They consist of two pulleys or wheels that are a certain distance appart. Their axles are parallel and they rotate simultaneously due to the effect of the belt. The rotation of one axle is transmitted to the other through the connected pulleys.
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Worm gears
This is a screw that moves a helical cogwheel that is set perpendicular to the screw. A worm screw fulfils this equation:
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Gear train
This is a system of more than two gears that are connected together. Each of the connected geared wheels rotate on the opposite direction to the wheel that it is attached to.
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Pulley trains with belts
The gear ratio between the drive pulley and the driven pulley depends on the relative size of the pulleys in the system. It is expressed by the next equation:
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Linear motion mechanisms
Levers
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Types of levers
Class 1
- The fulcrum is between the effort applied and the resistance - The effect of the effort applied can be multiplied or reduced
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Class 2
-The ressistance is between thwe fulcrum and the effort applied - -The effect of the effort is always multiplied (d>r)
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Class 3
- The effort applied is between the fulcrum and the resistance -The effect of the effort applied is always reduced
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Fixed pulley
A fixed pulley is balanced when the effort F is equal to the ressistance of the load, R (F = R). A fixed pulley is a wheel that groove around it into wich a rope, chain or belt fits.
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Movable pulley
A moveable pulley is a set of two pulleys (one is fixed with the other). A moveable pulley is balanced when it satisfies this equation: F = R/2
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Compound pulley
This is a system of fixed and moveable pulleys, often called block and tackle. When we use this the effort is less than with a fixed pulley or a moveable pulley. When the number of pulleys increases the less effort is needed to be aplied
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Around us we can see many objects and mechanisms that produce movement that we call motion also. There are diverse uses for the mechanisms: - transporting people from A to B - telling the time - entertaining children in the park - lifting and carrying objects The driving force can be a spring , an electric or our own muscles.
