Engineered Products

Skills of the Engineer (4), PS, D, C PM

• Problem solvers

• Designers

• Communicators

• Project managers

Problem Solvers

• Presented with a challenge or problem and then come up with a solution

Designers

• Final design would be tested then evaluated

Communicators

• Verbal, writen and graphical forms

• CAD, pictorial, orthogonal and assembly

Project Managers

• Ensure al parts of the project occur at the right time and on the right schedule and within constraints on materials and cost

Historical Development

Lawn Mowers

Car Development

Historical development of Lawn Mower

Different Types of Lawn Mowers over the years

1. John Ferrabee (1830)

2. Follows and Bate (1900)

3. Royal (1936)

4. Victa 2 Stroke (1950)

5. Victa 2 stroke (1960)

6. Sunbeam 2 stroke (1974)

7. Honda 4 stroke (2011)

1. John Ferabee (1830)

• The first push mower invested by Edward Budding in 1830

• Roller for regulating the height to prevent the machine from dropping into ground

• Front Mounted Catcher

MATERIALS

• Wrought iron and cast iron

• Cast iron → strong, durable, easy to cast, good for early manufacturing

• Wrought iron → tough, malleable, and far less brittle than cast iron.

2. Follows and Bate (1900)

• Catcher behind the main body of the mower

• Gear driven

• Timber Handles

  Lightweight and easy to shape with the tools available in 1900.

• Steel frame and gears High strength and toughness, allowing the mower to handle mechanical loads.

3. Royal (1936)

• Petrol engined domestic mower

• Chain drive and front mounted catcher

• Reel mower, reel doing the cuttin- A reel is a cylinder with multiple curved blades that spin forward

• Fabricated steel frame, engine uses cast iron

• Steel reel → tough + sharp

4. Victa 2 Stroke (1950)

• Cast iron base plate with no provision for catcher

• Handles painted tube steel

• Started by using a rope wrapped around a pulley at the top of the motor

• Tiresome, took many pulls

Cast iron base plate

– Very high compressive strength, making it durable under engine vibration.

5. Victa 2 Stroke (1960)

• Self propelled model

• Fuel tank and impulse starter

• Polyethelene catcher

6. Sunbeam Mower (1974)

• 160 cc two stroke motor

• Fuel tank, recoil starter

• Pipes exhaust fumes to reduce airbone pollution

7. Honda 4 Stoke ( 2011)

• Mulch and catch mower

• Base plate is cast aliminium

• Catcher is Poleyethelyne Terephtalte

• Offer choice between mulching and catching

• More versatile

Car Development

• First car- Gotleib Daimler

• Mass Produced using production line method

• Volkswagen- Most popular car

• Citroen DS19

• Transverse engine

Effect of Engineering on Peoples lives

• Lawn mowers

• Cars

Effect of Lawn mowers on peoples lives

• The sunbeam mower 1947, that any heavier than air pollutant were deposited directly on the ground

• Saves time and effort: Instead of cutting grass by hand, people can mow quickly.

• Better appearance: Keeps gardens, parks, and sports fields neat and well maintained.

Effect of Cars on peoples lives

• Development of 4 wheel brakes on in the mud to late 1930’s starts to make the car a much safer travel option

• Innovative suspension systems and disc brakes improved by dynamic safety

• By all 1972 all cars sold in Australia must have seatbelts

• 21st Century: Hybrid Car

Environmental Implications (Petrol Engine 4)

• Induction

• Compression

• Ignitiiton (Power)

• Exhaust

1. Induction

• The valves open

• The piston moves down

A piston is a tightly fitting component that moves up and down inside a cylinder to transfer force from expanding gases into mechanical motion.

What it does:

• Moves up and down

• Gets pushed by burning fuel gases

• Converts that push into motion for the engine

2. Compressin

• Valves are closed

• Pistons move up

3. Power

• Spark Plug igniting the compressed fuel mixture

• Piston goes down

4. Exhaust

• Exhaust valves open pushing the gases out of the cylinder

• Pistons move up

Nature and Types of forces

Concurrent- Pass through game point

Non concurrent- Intersect various points

Collinear- Lie on the same line

Resultants and Equilibrants

Resultant: The single force that has the same effect as all the forces acting together

Equilibrants: The force that balances the resultant

Principle of transmissibility of forces

• A force may be relocated at any position along its line of action, with the same magnitude, direction and sense, and still have the same effect.

Imagine you are pushing a shopping trolley in a straight line.

You apply a force of 50 N forward at the handle (top).

Now imagine the same 50 N force is applied at the middle of the trolley, still in the same straight direction.

In both cases:

The trolley moves the same way

The effect on its motion is unchanged

Three force rule for equilibirum ( Calculation)

Moment ( Calculation)

Couples ( Calculation)

Engineering Materials (very important) WH, HT, A

Modification of Materials

• Work hardneing

• Heat Treatment

• Alloying Materials

Work Hardening *metal becomes stron,, and hard,,,, after being plast__ defo__ at its recr___ temperatur

makes stronger but less fl__

• Work hardening is when a metal becomes stronger and harder after being plastically deformed (bent, stretched, hammered), at its “ recrsytillisation temperature” (stressed grains of a metal reform to unstressed)

• Makes it stronger but less flexible

As the metal deforms, the atoms slide across the shearplane, and dont move as they are encounter grain boundaries

Heat Treatement

• Heat treatment is the process of heating and cooling a metal in a controlled way to change its properties (like strength, hardness, or flexibility).

Steel ( Heat Treatment) FERROUS METALS ONLY

• Heated until red hot (1000 degree celscius) then quenched in water, the steel will become hard but brittle *easy to break.

Martensite

• Very hard structure formed when steel is rapidly cooled/ quenched

Tempered Martensite

• Quenched steel that has been reheated to reduce brittleness and increase toughness

Heat Treatment Process “ Steel”

Ferrite: Soft, ductile form of iron in steel

Pearlite: Layered structure of ferrite and cementite that increases strength

1. Annealing

2. Process Annealing

3. Normalising

4. Spherodising

5. Tempering

Annealing

• Steel is heated about 900 degrees and then cooled very slowly (usually in a furnace)

• Results in an unstressed grain structure consisting of ferrite and pearlite

Process Annealing

• Lower-temperature heating around 550-650 degrees on mild steel

• Ferrite phase undergoes recovery and recrystallisation, being unstressed

• Pearlite is less affected because its layered structure is more stable at these temperatures.

Normalising + produces finer grain stru__ then anneal…

• Steel heated up to 900 degrees to relieve stress, then cooled in air

• Produces a finer grain structure then annealing

Spherodising (softer)

• Occurs during a rehating after steel has been quenched in 650-700 degrees

• The cementite (Cementite a hard compound in steel made of iron and carbon), forms into spheroids in a soft ferrite matrix.

• HARD CEMENTITE BREAKS UP INTO ROUND PARTICLES RESULTING IN STEEL BEING SOFT, LESS BRITTLE, EASIER TO MACHINE

Tempering

• Reheating quenched steel to 200-600 degrees, then cooled to reduce brittleness and INCREASE TOUGHNESS

Non Ferrous Heat Treatment : JUST KNOW THE NAME

PRECIPITATION HARDENING

Other Materials Heat Treatment

• Glass can also be heat treated

Alloying Materials

• Elements that are added to a base metal (usually a metal like iron or aluminium) to change and improve its properties.

  
  

Alloying can create 2 types of solid solutions

• Substitutional solid solution

• Interstitial solid solution

Substituional solid solution *atoms

• Atoms must be similar in size

Interstitial solid solution

• Atoms must be much smaller

Diagram of the 2

a- solid

b- inter

Engineering Applications of Materials ( Material suitability)

• Specific strenth

• Corrosion resistance

• Resistance to fatigue

• Hardness and Toughness

Electricty

• Electricity: The flow of electrons through a system

Current (I)

• Measure of quantity of electrons flowing per second

• Units: A

Potential Difference (E)

• Voltage, Electromotive force (EMF)

• Measure of electric pressure forcing electrons through a system

• Units : (V)

Resistance (R)

• The amount of resistance exhibited by a system

• Units: _M_

Ohms Law

V=IR

• Potential difference= Current x Resistance

Voltage drop

Subtract from intial voltage

Resistance formula (resistivi__, x leng/ area

Area is always cross sectional

so PI R 2

OR PI X DIAMATER DIVIDED BY 4

Electrical Safety

• A lot of modern domestic appliances are double insulated

Induction Motors (only know the name) and How it works, Used

• electrictuy flows in ___ coils

• Spinning m__ field

• Creates Curr__

• Rotor spi__

• There are vairous diferent types of induction motors “ The Squirrel cage”

An induction motor is a specific type of electric motor.

• Electricity flows in the outside coils (stator)

• This creates a spinning magnetic field

• That spinning field induces (creates) current in the inner part (rotor)

• The rotor then gets pulled along and starts spinning

Used in

• Fans

• Refrigerators

• Lathes

Electric Motors ( what induction motor falls in)

• Electric Motors convert electric energy into mechanical energy, a generator does the opposite

How electric motors work?

• A standard electric motor passes current through a rotating coil

• The coil will have a magnetic field created around it which will react with the magnetic field surrounding it.

DC motor

1. Electricity flows in through a ring ( Commutator)

2. Spins in contact with brushes

DC = brushes + split ring needed

AC motor

1. AC electricity flows in

2. Current already changes direction (Alternating Current)

3. Creates a changing magnetic field

4. Rotor spins continuously

DC: current supplied through brushes + spinning ring, and the ring switches direction

AC: current already switches itself, so no ring needed

Back EMF *voltage

Supply EMF: the voltage supplied by a power source that drives current in a circuit.

Back EMF: the voltage produced in a motor that opposes the supply voltage when it is running.

Series and Parallel Resistors

• Series = R1 + R2 + R3…

• Parallel

Conductivity

• The reciprocal of resitivity

• Low resisitivity means high conductivity

• UNITS= Siemans per meter

Simple Circuit and Components ( Drawing)

Memorise All

Features of the commonly used electric components

• Switches

• Cell

• Battery

• Resistor

• Potentiomater

• Capacitor

• Electrolytics Capacitor

• Diode

• Light emitting Diode

• Transistor

• Motor

• Loudspeaker

Switches

• Allow the operator to control the flow of electricity in the appliance

Cell

• Devise used to proudce electricity

Battery

• A group of cells connected together

Potentiometer

• Variable resistor, ( resistance might be increased or decreased)

Capacitor

• Device capable of storing an electric charge

Electrolytic Capacitor

• A special capacitor whch has polarity

• Polarity ( Both negative and positive charge)

Diode

• A Diode only allows current to flow in one direction

Light Emitting Diode ( LED)

• A diode that emits light

Transistor

• Acts like a switch or amplifier

Motor

• Converts electricity into rotary motion

Loudspeaker

• Used to emit warning sounds on appliances

AC and DC circuits

AC and DC Transimissons

• AC = easy to change voltage → used in power grids

• DC = efficient for very long distances → used in special situations

Dimensioning