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Mechanisms (Rotary motion mechanism (Variation in velocity (Apart from…
Mechanisms
Mechanisms
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The most important element in all of them is the driving force that initiates the movement. The drivng force can be a spring, an electric motor or our own muscles.
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Linear motion mechanisms
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·Levers
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-F: is the force or effort .
-R: is the resistance or load.
-d: is the distance between F and the fulcrum.
-r: is the distance between R and the fulcrum.
·Law of a lever: It's F · d = R · r
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·Fixed pulley: It's a wheel that has a groove around it into which a rope, cham or belt fits. F = R
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·Compound pulley
This ts a system of fixed and moveable
pulleys, often called block and tackle.
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Rotary motion mechanism
Friction drives
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When primary drive wheel moves, it turns or drives the second or output wheel causing it to move as well. The output wheel rotates in the opposite direction of the pnmary wheel
·Formula: N1 · N2 = D1· D2 ---> N1/N2 = D2/D1
N are the velocites of primary wheel and the output wheel
D are the diameters
Pulleys with belt
They consist of two pulleys or wheels that are e a certain distance a part, 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 connected pulleys. The two pulleys, and the two axles, rotate in the same direction
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Worm gear
This is a screw that moves a helical cogwheel that is set perpendicular to the screw.
·Formula: N wheel = N screw · Z grooves / Z wheel.
N--> velocities Z grooves--> number of grooves of the screw
Z wheel-->number of teeth of the wheel
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Gear train
This is a system of more than two gears, connected together.
·Formula: N4/N1 = Z1 · Z3 / Z2 · Z4
N--> velocities Z--> number of teeth
Pulley trains with belts
It's a system of pulleys, or wheels, with a belt
formed by more than two wheels.
·Formula: N4/N1 = D1 · D3 / D2 · D4
N--> velocities D--> diameters of each wheel
Variation in velocity
Apart from transmitting force and motion, rotary transmission mechanisms allow velocity to vary.
·When the wheels and the gears have the same diameter or the same number of teeth, they rotate at the same velocity.
·When they' re different sizes, th» smallest rotates more quickly.
The ratio of the velocities of the two wheels is given by the gear ratio
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