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MECHANISMS - Coggle Diagram
MECHANISMS
Rotary motion mechanisms:
Friction drives: Are made up of two or more wheels that are in contact.
First wheel is called primary drive wheel; second is called output wheel.
D1/D2=N2/N1 or D1xN1=D2xN2
Pulleys with belt: Two pulleys that are a certain distance apart.
Their axels are parallel amd they rotate simultaneously.
Gear mechanisms and cogwheels
Are sets of wheels that have teeth called cogs. They transmit rotatory motion between the two conneted axles.
N=Speed; Z=Numbers of teeth. N1xZ1=N2xZ2
Worm gear
Is a screw that moves a helical cogwheel that is set perpendicular.
N wheel= Nscrew x Zgrooves/Zwheels
Gear mechanism with a chain
These are two cogwheels with a metal chain.
Gear train
Is a system of more than two wheels connected together.
Pulley trains with belts
Is a system of pulleys or wheels with a belt
Variation in velocity
If the wheels are the same, they have the same speed, but if they are different, the smallest one is faster.
Other mechanisms
Mechanisms for controlling and direction motion:
The ratchet is very common, and they all use brakes
Brakes: Disc brakes: Consits of pads and a disc; Band brakes: A metal band that puts pressure on a drum; Drum brakes: Include one or two brake shores.
Mechanisms that store energy:
Springs are devices that absorb energy.
By compression: The spring is compressed; By traction: The spring is stretched; By torsion: The spring is twisted
Connecting mechanisms:
Clutches connect axles
Fixed connections: permanent connections; Movable connections: Connect shafts and aren't permanent
Supports: bushings and bearings
In bushings te axle or the saft is inserted in a plain circular piece.
Bearings are made up of two concentric rings with balls between them.
Mechanisms that transform motion
From rotatory into linear
Rack and pinion system:
Uses a pinion mounted on a rack. L=PxNxZ
Nut and bolt system:
Consists of a bolt and a nut with the same diameter.
Winch and crack handle
Consists of a drum that rotates and a crack handle that allows to pull objects.
From rotatory into reciproacting motion
Crank-link-slider
This is composed of a crank and a rod called connecting link.
Crank shaft
This is a set of connecting rods attached to a joined axle. Each of the joints acts as a crank.
Cam
Is a rotating object that pushes a follower as it moves
Eccentric cam
Is a wheel with an off-centre rotation axle that doesn't coincide with the centre of the semicircunference.
They have diverse uses. The most important element in all of them is the driving force.
The driving force can be a spring, an electric motor or our own
muscles.
Linear motion mechanisms:
Levers:
Are rigid bars that are supported by a fulcrum.
-F is the force or effort; R is the resistance or load; d is the distance from F to the fulcrum; r is the distance from R to the fulcrum.
Types of levers: Class 1: The fulcrum is between F and R; Class 2: R is between F and the fulcrum; Class 3: F is between R and the fulcrum.
Pulleys: Fixed pulleys: F=R; Movable pulley: F=R/2; Compound pulley: F=R/2xn or F=R/2 elevated to n.
