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Mechanisms:Mechanisms are devices that transmit and convert forces and…
Mechanisms:Mechanisms are devices that transmit and convert forces and motion from a
driving force or input element to an output element.
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Linear motion mechanisms
Fixed pulley:
A fixed pulley is balanced when the effort F is equal to the resistance of the load, R: F=R
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Compound pulley
This is a system of fixed and moveable pulleys, often called block and
tackle.
These mechanisms transmit motion and effort in a circular way, from the input to the output
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Gear mechanisms with a chain These are two cogwheels with parallel axles that are a certain distance apart, they rotate simultaneously by means of a metal chain or a toothed belt stretched over both wheels
Gear mechanisms and cogwheels: Cogwheels are sets of wheels that have teeth called cogs The ratio between the rotation veloaues of the wheels depends on the
number of teeth on each wheel.
Gear train This is a system of more than two gears, connected together as shown in
the diagram.
The rotary motion of the first wheel drives the second wheel and
so on
Pulleys with belt:They consist of two pulleys or wheels that are a certain distance apart.Their axles are parallel and they rotate simultaneously due to the effect of the belt
Pulley trains with belts:The rotary motion of axle 1 is transmitted to axle 2 by the belt that connects them. Pulleys 2 and 3 rotate at the same velocity The motion of pulley 3 is transmitted topulley 4 by the belt that connects them. All the wheels rotate m the same
direction
Friction drives:The first wheel is called the primary drive wheeL When it moves, it turns or drives the second or output wheel, causing it to move as well.I he ratio between the rotation veloaty of the wheels or pulleys depends on the relative size of the wheels.
Mechanisms that transform motion: There are two ways in which motion can be transformed:
from rotary into linear
from rotary into reciprocating
From rotary into linear
Nut and bolt system: This consists of a bolt or threaded bar and a nut that has the same
intenor diameter as the diameter of the bolt.
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Rack and pinion system: This uses a pinion that is a small cogwheel, mounted on a rack that is a
toothed belt or bar
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Other mecanisms
Mechanisms for controlling and directing motion: The most typical mechanism of this type is the ratchet, which allows rotauon in one direction but impedes it in the opposite direction, as you can see in the diagram Disc brakes consist of pads and a disc anached to the oblect that we
want to slow down
Band brakes consist of a metal band that puts pressure on a drum
attached to the axle of the oblect we want to slow down.
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Mechanisms that store energy: Springs are devices that absorb energy This energy can be released
later, little by little or all at once.
By traction. The spnng is stretched, in a bed frame for example.
By torsion. The spnng is twisted, in a clothes peg for example
By compression. The spnng is compressed, in a chair for example.
Connecting mechanisms:
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Movable connections are used to connect shafts that can move
along the axle or at an angle to each other. There are two main types: Oldham iomts and Cardan joints.
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