MECHANIMS

  1. MECHANIMS

around us we can see many moving objects and mechanims that produce movements that we can also call motion.

telling the time

entertaining children in trhe park

transporting people from A to B

lifitng and carrying objects

Mechanims are devides that transmit and convert forces and motion from a driving force or inpuut element to and output element.
they allow us to carry out certain tasks more easily and more efficienly

2.LINEAR MOTION MECHANIMS: Mechanims that transmit motion and force in a stright line from one point to another.

2.1.Levers

·F is force or effort applied at one and of the bar

·R is the resistance or load which acts at the other end of the bar

·r is the distance from R to the fulcrum

·d is the distance from F to the fulcrum

The following equation inicastes a balanced lever:
F·d= R·r
it's called the law of the lever

2.2. Fixed pulley

A fixed pulley is balanced when the efoort F is equal to the resistance of the load, R
F=R

2.3. Movable pulley

A moveable puley is balanced when it
satisfies this equation
F=R/2

2.4. compouns pulley

This is a system of fixed and moveable pulleys, often called block and
tackle.

  1. ROTARY MOTION MECHANIMS

3.1. Friction drivers

I he ratio between the rotation veloaty of the wheels or pulleys depends on
the relative size of the wheels.
It is expressed by the followmg equation:
N1·D1=N2·D2 - D1/D2=N1/N2

N1 and N2 are the velocities of the primary drive wheel and the
output wheel
D2 and D2 are the corresponding diameters
They are expressed in units of length: usually millimetre

3.2. 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.

3.3. Gear mechanisms and cogwheels

The ratio between the rotation veloaues of the wheels depends on the
number of teeth on each wheel. It's expressed by this equation:
N1·Z1=N2·Z2 - Z1/Z2=N1/N2

3.4. worm grear

A worm screw fulfils this equation: Nwheel= Nscrew·Zgroovers/Zwheel

3.5. Gear mechanisms with a chain

The relation between the rotation veloaties of the wheels depends on the
number ofteeth on each gear.
N1·Z1=N2·Z2 - Z1/Z2=N1/N2

3.6. grear train

The gear ratio between the drive wheel (I) and the dnven wheel (4) depends
on the number ol geared teeth m the system
N4/N1= Z1·Z3/Z2·Z4

3.7. Pulley trains with belts

The gear rauo between the dnve pulley (I) and the dnven pulley l4) depends
on the relauve size of the pulleys in the system. It's expressed as a function of their diameters.
N4/N1= D1·D3/D2·D4

4 MECHANISMS THAT TRANSFORM
MOTION:
·from rotary into linear
·from rotary into reciprocating

4.1. From rotary into linear

P is the distance between two consecutive teeth in milimetres

Z is the number of teeth in the pinion

L is the velocity of the rack's movement in milimdetres per minute

N is the number of rotations per minute of the pinion

Nut and bolt system

Winch and crank handle

4.2. From rotary into reciprocating

Cranlshaft

Cam

Crank-link-slider

Eccentric cam

5-OTHER MECHANISMS

5.1. Mechanisms for controlling

The most typical mechanism of this type is the ratchet, which allows rotation in one direction but impedes it in the opposite direction, as you can see in the diagram

· disc brakes · band brakes · drum brakes

5.2. mechanisms that store energy

By traction

By torsion

By compression

5.3. connecting mechanisms

·FIXED CONNECTIONS

·MOVABLE CONNECTIONS

·CLUTCHES

5.4. supports: bushimg and bearings

bearings are made up of two concentric rings balls or rollers between them

in bushing the axle or the shaft is inserted in a plain circular piece