MECHANISMS
They're classified in:
Transmitting Motion
Transforming Motion
Linear
Rotary
Rotary to Linear
Rotary to Reciprocating
LINEAR MOTION
Definition: Mechanisms that transmit motion and force in a straight line from one point to another.
Levers
A lever is a rigid bar that is supported by a fulcrum.
The Law of levers: F · d = R · r
There are 3 class of levers
Class 2: The resistance is between the fulcrum and the effort applied.
Class 3: The effort applied is between the fulcrum and the resistance.
Class 1: The fulcrum is between the effort applied and the resistance.
Fixed Pulleys
A fixed pulley is a wheel that has a groove around lt into which a rope, cham or belt fits It rotates around an axle that is fixed to an immobile surface.
Law: F=R
Movable Pulleys
A moveable pulley is a set of two pulleys — one is fixed while the other can move in a linear direction.
Law: F=R/2
Compound Pulleys
This ts a system of fixed and moveable pulleys, often called block and tackle
Block Law: F=R/2n
Tackle Law: F=R/2N
ROTARY MOTION MECHANISMS
Friction Drives
Pulleys whit Belt
Friction drives are made up of two or more wheels that are in contact
N1· D1 = N2 · D2 -> D1/D2 = N1/N2
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.
Gear Mechanisms and Cogwheels
Cogwheels are sets of wheels that have teeth called cogs. The cogs fit into the spaces between the cogs of another wheel, so that one wheel moves the other.
N1 · Z1 = N2 · Z2 -> N1/N2 = Z1/Z2
Worm Gear
This is a screw that moves a helical cogwheel that is set perpendicular to the screw
N = N · Z / Z
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.
N1 · Z1 = N2 · Z2 -> Z1/Z2 = N2/N1
Gear Train
This is a system of more than two gears, connected together
N4/N1 = Z1/Z2 · Z3/Z4
Pulley Trains With Belts
Look at the diagram below. It's a system of pulleys, or wheels, with a belt formed by more than two wheels.
N4/N1 = D1/D2 · D3/D4
MECHANISMS THAT TRANSFORM MOTION
From Rotary Into Linear
From Rotary Into Reciprocating Motion
Nut and bolt system
Winch and crank handle
Rack and pinion system
This uses a pinion that is a small cogwheel, mounted on a rack that is a toothed belt or bar
L = P · Z · N
This consists of a bolt or threaded bar and a nut that has the same intenor diameter as the diameter of the bolt.
A winch and crank handle system consists of a drum that rotates and a crank handle that allows to pull or lift obiects.
F · d = R · r -> F = R · R · r / d
Crank-link-slider
Crankshaft
This is composed of a crank and a rod called a connecting rod or link. This rod has articulated Ioints at each end — one is connected to the crank and the other to the slider
This is a set of connecting rods attached to a jointed axle. Each of the joints of the axle acts as a crank
Cam
This is basically a rotating object that pushes a follower as it moves.
Eccentric cam
This consists of a wheel with an off centre rotation axle that doesn't coincide with the centre of its circumference.
OTHER MECHANISMS
Mechanisms for Controlling and Directing Motion
Mechanisms That Store Energy
The most typical mechanism of this type is the ratchet, which allows rotauon in one direction but impedes it in the opposite direction.
Springs are devices that absorb energy This energy can be released later, little by little or all at once.
Connecting Mechanism
Movable connections are used to connect shafts that can move along the axle or at an angle to each other
Fixed connections are used to make permanent connections
between axles and shafts
Clutches are mechanisms that allow axles or shafts to be connected or separated
Supports: Bushings and Bearings
In bushings the axle or the shaft is inserted in a plain circular piece that is placed inside a housing to provide a bearing surface.
Bearings are made up of two concentric nngs with balls or rollers between them.