GCSE DT (Graphics) (copy)

3 sections: A (core technical principles, 20 marks), B (specialist technical principles, 30 marks), C (designing & making principles, 50 marks), 2 hours, 100 marks, 50% of GCSE

automation

using automatic equipment in production

automation has been developing in factories since the industrial revolution, with machinery being used to complete tasks previously done by humans

automated machines are programmed to carry out a procedure multiple times to improve production times. automation has streamlined the manufacturing system by increasing production & reducing errors

setup costs of machinery is high but when the machines are operating less waste is produced and running costs are lower

the use of automation in workplaces has led to an increase in skilled workers but a decrease in job opportunities

robotics

the use of robotics is one part of automation but robots different to automation because they use AI to collect info & improve the performance of a procedure

robotics is popular because of its ability to increase efficiency and handle harmful materials humans can’t, but they are very expensive

specialist buildings

smart technology has improved the efficiency of buildings, with many factories using renewable energy sources to try to minimise environmental impact

modular buildings can be erected quickly & at a low cost, and improvements in stock control mean less storage space is needed

smart technology

technology that uses a chip to store information

modular building

a building made of smaller prebuilt parts & put together

crowdfunding

traditionally new businesses would borrow money from a bank to raise enough funds to develop a project. but this is risky and can be expensive due to interest payments

crowdfunding uses websites to advertise products as investment opportunities where people can choose to back a project with a financial donation if they think it will be viable & work successfully

backers are often rewarded with free gifts, discounts or a pre-agreed part of any profits if the product is succesful

virtual marketing & retail

promotion of products online & sharing experiences, reviews and recommendations has rapidly become part of the retain experience

algorithms can generate info about users’ buying habits and suggest relevant retail sites for them using search engine optimisation (SEO)

blogs, vlogs and social media all provide advertising platforms and costs of retailing from a website are far lower than from a high street shop

search engine optimisation (SEO)

the process of using techniques to improve return rate of a webpage when indexed by a search engine

cooperatives

organisations with lots of people working together towards common goals. run and owned by members who share decision making, profits & risk

UK examples: the co-operative group (co-op), nationwide building society

fair trade

trade in which fair prices are paid to the farmers & workers who create products

a trading partnership / principle where fair prices & wages are paid are paid to workers especially in developing countries & safe suitable working conditions are ensured throughout the manufacutring chain

sets minimum standards for pay & conditions:

• workers are paid a fair wage

• working conditions are monitored & kept safe

• safety equipment (goggles, guards) is enocuraged

• harmful / toxic chemicals are reduced / replaced

• sweatshops, child labour & exploitation are banned

not a legal requirement but has become popular due to ethical concerns from designers & consumers. many companies choose to fair trade endorse products to reflect their belief that workers should be treated well & to support sales

sustainable

able to be maintained at a certain rate / level. a sustainable resource can be replaced once used e.g. as a tree is chopped down many more can be planted to ensure the use of trees can be sustained

finite resources

resources that can only be used once and are in limited supply - non-renewable resources that will eventually run out e.g. metals, plastics, fossil fuels (coal, natural gas, oil)

popular as they are easily accessible (due to strong supply chains) and often have benefits for manufacturing particular products or for energy supplies

many companies have become more careful in their use of finite resources and they consider the ecological footprint carried by using such materials. but not all companies do this and some still rely on finite resources even though their use damages the environment.

fossil fuels

natural, finite fuel formed from the remains of living organisms e.g. oil, coal, natural gas

they are a finite resource so they can’t be replaced once extracted from the ground. more than 80% of the world’s energy comes from fossil fuels

ecological footprint

an analytical measurement of the amount of global resources used

non-finite resources

renewable energies that harness earth’s natural resources. found naturally and can be replaced e.g. wood, cotton, renewable energy sources (solar, wind)

renewable energy

power that’s generated using natural resources that won’t run out. they are a non-finite resource as they harness the earth’s natural resources

examples include wind, solar, tidal, hydroelectric, biomass

in 2018 around 1/3 of the UK’s electricity was generated from renewable energy resources

waste disposal

how materials & resources are disposed of is carefully monitored & managed by local councils. households are encouraged to recycle waste items where possible, including products made from materials like hard plastics, paper & steel, as well as natural garden waste

in 2016 the uk recycled 25% of household waste with the target of 50% in 2020

all other waste goes to landfill site which release harmful gases that pollute the surrounding air & soil

landfill sites

places where refuse is buried underground

continuous improvement / kaizen

the practise of continually making small adjustments to production techniques to improve speed & quality and save resources, improving the way a company works

encourages people to work together & give regular feedback to make small improvements, in order to increase productivity and create team harmony

known in manufacturing, healthcare & services industries by the japanese name ‘kaizen’

efficient working

its important for companies to work efficiently. this includes speed of production, reducing errors, and reducing waste, which can be done by utilising automation or CAM

implementing quality control checks ensures that errors are quickly spotted and provides the customer with reassurance

computer aided manufacture (CAM)

the manufacture of a part / product from a computer aided design (CAD) using computer-controlled machinery e.g. 3D printers, laser cutters, milling machines

advantages:

• fast & accurate production

• machines can run constantly on repetitive tasks

disadvantages:

• expensive to set up

• needs a skilled workforce of engineers

pollution

pollution is caused when harmful substances are released into the natural environment - can occur in the air, water or natural land

legislation has been brought in to help the issue e.g. uk cosmetic product can’t contain plastic microbeads any more - banned in the uk in 2018 as they were polluting the ocean

harmful products (e.g. batteries) should be disposed of correctly and companies are being encouraged by government incentives (benefits given by the government) to recycle waste wherever possible

global warming

the rise in the average temperature of the earth’s surface

manufacturing processes in factories & the use of day to day product like cars can cause harmful chemicals (e.g. carbon monoxide & nitrogen oxides) to be released. these chemicals pollute their & natural land

worldwide environmental awareness has led to limitations on the levels of pollution and emissions of greenhouse gases, as well as targets on renewable energy generation to try to stop global warming

development of more efficient electrical products (e.g. low energy light bulbs & better building insulation) has cut down on energy costs. some countries offer incentives to increase the use of emission controls, electric vehicles and energy saving devices e.g. better insulation & automatic shut off devices

technology push

when technology advances enough to invent / develop new products

research & development in science & industry leads to new discoveries which can be used to improve existing products or develop new ones

happens before there is a consumer demand for a product

research & development is valuable for companies who are the first to introduce a new innovative product

example: smartphones developed due to technology push - existing touchscreen technology was used to improve the mobile phone market

greenhouse gases

the gases responsible for global warming & climate change: carbon dioxide, methane, nitrous oxide, CFCs (chlorofluorocarbons)

consumer

(in business) a person who uses a product & may also buy it

market pull

when consumer demand forces the invention / development of a new product

product ideas are produced in response to market forces or customer needs e.g. development of cameras to become smaller, more lightweight & higher performing due to customer needs

change in job roles

rapid changes in technology & automation in recent years have led to a decline in the need for traditional skills (manufacturing techniques used before automation)

rather than facing unemployment, workers have had to be retrained or up-skilled to manage new technologies

e.g. robotics - employee needs to understand how a robot is programmed & can be controlled to perform a task, rather than performing the manual task themselves

changes in fashion trends

fashion trends are influenced by changing technology. wearable items embrace new tech e.g. high-tech watches, and textile technology utilises electrically conductive material or 3D printing technology

embracing new technology allows products to remain popular with a modern market while creating new & innovative looks (e.g. dress with 3D printed panels)

trend forecasts are able to predict the future patterns and colours 2 years before products come onto the market. manufacturers can buy this info to influence their designs & enable them to keep ahead of their market competitors (other producers who sell similar products)

manufacturer

a person/company that makes something from raw materials or from an assembly of component parts

market compatitor

another producer who sells similar products

respecting faiths & beliefs

many countries have a diverse range of cultures so it’s important for designers to consider a range of cultural beliefs when designing for the mass market.

clothes designers could incorporate designs into collections that allow customers from other cultures to dress more modestly. cosmetics manufacturers may choose not to use animal ingredients because of people’s beliefs

designer

someone responsible for planning the layout or structure of a piece of work e.g. a poster, website or computer game

mass market

the market for goods produced in large numbers

impact on society

not all products are designed for the mass market - some groups of people have specific needs that need to be met. this can be achieved through inclusive design or specific products

impact on society - physical disabilities

products aimed at users with physical disabilities ensure they can use the product with ease. user needs are met by understanding the nature of the disability e.g. visual impairments, mobility restrictions, motor control.

impact on society - age

when designing products aimed at elderly users it’s important to understand the difficulties users may experience - mobility issues, visual impairments, hearing loss

eg a long shoehorn will allow an elderly person to put a shoe on without having to bend down

impact on society - religious groups

religious groups have a variety of preferences that can be addressed through design - use of certain symbols, dietary restrictions & clothing requirements all need to be considered

computer aided design (CAD)

can design new products in 3D, visualise them in a variety of materials and send image around the world for collaboration & consultation. once production is finalised these designs are sent to CAM machines (like Autodesk & Solidworks) to be formed

advantages:

• designs can be drawn & developed quickly

• design can be viewed from all angles + with a range of materials

• some testing & consumer feedback can be done before costly production

disadvantages:

• expensive to set up

• needs a skilled workforce

• hard to keep up with constantly changing & improving technology

flexible manufacturing systems (FMS)

a series of different machines producing different parts for a product. flexible because machines can be reprogrammed at any time to change their task, and production can be changed to produce more/fewer parts without stopping other areas of the process

just in time manufacturing (JIT)

triggered by a customer order. correct amounts of materials are ordered in for the order and arrive just as they are needed by production

saves money on storage, reduces waste, ensures there’s no money wasted on producing stock that won’t be sold

disadvantages - if any part of the product can’t be sourced, clients will have to wait

lean manufacturing

Japanese concept based on minimising costs & maximising efficiency by cutting down on waste and the amount of materials & energy used in production

this is done by adapting designs and making changes to the production process. eg to reduce waste a product can be redesigned to include a tessellating pattern, to improve efficiency changeover times between production runs could be reduced

planned obsolescence

designing products that will have a limited life and will become obsolete and require to be replaced eg disposable razors or modern mobile phones as they need continual software upgrades and are soon replaced by new better performing models

generally bad for the environment as it creates more waste

design for maintenance

designing products that are more durable and have spare parts available to mend & maintain them. only possible with low tech or modular products that don’t require lots of skill to repair eg a push bike can be regularly maintained with parts like pedals & chains being replaced

design for disassembly

when a product has reached the end of its life it can be taken apart and the parts can be reused or recycled eg a stool could be unscrewed to allow the seat & legs to be recycled

environmental design

can be achieved by:

• making products from renewable materials to create less waste material eg paper straws

• transporting materials in a more efficient way to cut down on greenhouse gas emissions

• cutting down the use of finite resources in production & energy supply

fossil fuels - coal

in a coal power station coal is crushes into a fine powder before being burned. the hot coal heats water, turning it into steam. steam builds up into a very high pressure and this is used to spin a turbine, which is connected to an electrical generator which generates electricity

coal is no longer used to generate electricity in the UK

advantages:

• there’s enough coal on earth to last 100s of years

• produces high amounts of energy

disadvantages:

• produces carbon dioxide when burned which contributes to global warming

• damage is caused to natural land when mining

fossil fuels - natural gas

accounts for around 30% of the UK’s energy production. used for heating & cooking and is one of the main sources of power for electricity production in the UK

natural gas is most commonly produced off shore and transported trough pipelines to a gas-powered electricity power station

advantages:

• emits less CO2 than coal or oil

• existing infrastructure makes it easy to transport & use

disadvantages:

• highly flammable so if there’s a gas leak an explosion can easily happen

• non-renewable so supplies will eventually run out

in the UK there are shale gas (gas trapped in shale rock) deposits, which are obtained through fracking. there’s lots of discussion about whether this should be used - concerns about damage to land & release of harmful gases. fracking isn’t currently allowed in the UK

fracking

a process of forcing liquid & sand into shale rock to force oil or gas out

fossil fuels - oil

in the UK oil is mainly used for fuel or it’s turned into plastics. but a very small amount is burned to heat water, creating steam to generate electricity

advantages:

• small amount can produce lots of energy

• relatively easy to store & transport

disadvantages:

• creates significant air pollution when burned

• considerable impact on water, land use & disposal

nuclear power

nuclear energy generates ~15% of the UK’s energy. a huge amount of energy can be produced through the nuclear process using a relatively small around of uranium.

energy is produced as heat throughout fission - atoms are split and the energy is used to convert water into super-heated steam which spins turbines to produce energy

advantages:

• no harmful gases released

• more efficient than fossil fuels

disadvantages:

• power stations have to close after around 40 years of use when the uranium becomes less efficient at heating the water

• disposal of uranium is difficult & costly

wind energy

harnessed through wind turbines - the blades turn with the wind, driving a generator which produces the electricity. there are many dotted around the countryside, but they are now more commonly grouped together off-shore in large quantities to form a wind farm

advantages:

• constantly available & sustainable

• no cost for wind + running cost of turbines are relatively low

disadvantages:

• periods of low wind = little/no energy produced

• cost a lot to build & put in place

• some people don’t like the look of turbines / think they spoil the natural landscape

solar energy

solar panels are made from photovoltaic cells which harness the sun’s light energy & convert it into electricity

solar power provides clean energy from a plentiful supply, but there is still development work to be done to make solar panels more efficient. the placement is also important to ensure they track the path of the sun & harness the optimum amount of solar energy

advantages:

• clean, renewable energy source

• reduces household energy bills

disadvantages:

• some people don’t like the look of solar panels / feel they spoil the appearance of a building

• cost a lot to install

• doesn’t produce as much electricity when there is cloud cover eg during winter / night

tidal energy

tidal energy relies on the gravitational pull of the moon which causes the change in water levels (tides). the UK only generates a small amount of energy from tidal power but it’s estimated that the UK could potentialy harness around 1/5 of its electricity demand this way

a tidal barrage (dam) is built across the mouth of a river where it meets the ocean so that the incoming (and outgoing) tide passes through turbines to generate electricity

advantages:

• clean & renewable

• tidal power plants last for a long time

• could produce 1/5 of the UK’s energy (island)

disadvantages:

• construction of barrages is expensive

• environmental impact of barrages is unknown

hydroelectricity

uses a dam to block a valley / major river, often creating a reservoir behind. when water has built up behind the dam it’s directed & released by valves through turbines, which turn generators to produce electricity

advantages:

• clean & renewable

• valves can be opened quickly to produce energy at peak times

• no pollution when running

disadvantages:

• dam construction is expensive

• objections from people in surrounding environment

• affects the wildlife by flooding the valley

biomass energy

growing plants / using animal materials so they can be burned to produce heat. plants like rapeseed or willow are specifically grown as biomass crops so they can be burned in a furnace

advantages:

• clean & renewable

• CO2 is released in the process & can be reused by plants

• replacement plants can be grown quickly to ensure good supply

disadvantages:

• creates atmospheric pollution

• land use for energy crops may be needed for other purposes eg agriculture

energy storage - batteris

2 main types - single use & rechargeable. single use batteries (aka primary types) are commonly alkaline batteries and are readily available in supermarkets & shops

batteries are available in a range of sizes & shapes eg tiny button-cell batteries that power calculators & hearing aids or large batteries powering cars & trucks

AA and AAA are common forms used in homes. both typically produce around 1.5V per battery. a larger PP3 battery used for smoke alarms & medical equipment produces 9V per battery

once a battery runs out it has to be replaced unless it’s rechargeable, in which case it is connected to a mains power source to be recharged

rechargeable batteries are more expensive than single-use but can be recharged so are more economical in the long term. however they have a limited lifespan - they can only be recharged a number of times before they lose battery life (eg smartphone batteries)

batteries can be recycled to prevent them ending up in landfill sites - they contain harmful chemicals & metals that are bad for the environment if disposed of incorrectly. they can contaminate the ground or poison wildlife that eat them

energy storage - kinetic-pumped storage system

a fast acting electrical energy storage system used to top up the national grid power supply at peak times when more electricity is needed. works by having 2 reservoirs and a hydroelectric dam system

during the night excess electricity is produced by other energy stations meaning the cost of electricity is much lower. during this time the kinetic-pump plant will pump water from a lower reservoir to a higher one. when there is a sudden need for more electricity (spike) during the day, the dam is opened and the water from the top reservoir spins the turbines to quickly produce the energy needed

traditional materials

materials that have been in use for centuries like paper, wood, stone & metals

modern materials - graphene

a single carbon layer material which is hypothetically 100x stronger than steel, but we haven’t manufactured it in large enough quantities yet. in theory it could provide body armour which is bulletproof, invisible & almost weightless

modern materials - titanium

a modern metal used in sport & medical applications like replacement hip joints & high performance bicycles. it has a high strength-to-weight ratio and is corrosion resistant

modern materials - metal foams

metal foams are strong but lightweight and are produced by injecting gas or foaming agent into molten metal. only 5-25% of the foam is metal, allowing the material to retain its strength but without its density / weight. often used in vehicles like planes & cars as they can absorb shock in a crash

modern materials - LCDs & OLEDs

liquid crystal displays (LCDs) use the light-modulating properties of liquid crystals (which are between a liquid & solid state) to display an image. when charge is applied to each crystal the shape changes to block light or let it through

LCDs require a backlight to work & many modern devices now use organic light-emitting diodes (OLEDs) instead, which allows devices to be thinner & lighter. OLEDs are more expensive as each pixel is its own light but they allow for thinner panels and better colour & contrast

modern materials - nanomaterials

tiny particles (1-100 nanometres) that can be used in thin films or coatings like the oleophobic coatings on phone screens that repel greasy fingerprints, or hydrophobic materials that repel water

modern materials

a material that has been engineered to have improved properties

smart materials

while smart materials are modern materials, not all modern materials are smart. to be classified as a smart material, they need to exhibit a physical change in response to some external stimuli - they have to change when you do something to them, and when you remove it they return to their original form

smart materials - shape-memory alloys (SMA)

metal alloys that can remember their shape when heated. they have been utilised on spectacle frames that spring back to shape if they’re squashed

nickel titanium (nitinol) is a type of SMA that contracts when heated (instead of expanding like most materials). braces made form nitinol heat up in the mouth and pull on the teeth so they move with it

smart materials - thermochromic pigments

change colour when their temperature changes. can be mixed with paint or polymers to give the materials the same colour-changing properties eg colour changing mugs or kids bath items

smart materials - photochromic pigments

change their properties when exposed to UV light eg glasses with clear lenses inside & sunglasses when exposed to bright sunlight, or windows that prevent rooms from getting too hot in warm weather

smart materials - quantum-tunnelling composite (QTC)

an insulating rubber containing tiny particles of metal. when squashed the metal particles meet & allow the flow of electrical current - so QTC is an insulator when resting and a conductor when pressure is applied

often used in outdoor applications where water might otherwise damage tiny microswitches. it’s also been used in clothing to control smartphones & portable music players, and in power tools to give variable speed controls in touch-sensitive pads

smart materials - self-healing materials

have the ability to repair themselves, extending the lifespan of the products that use them. examples include polymers that can heal knife cuts in themselves, metals that resist corrosion and concrete that can heal when cracked

smart materials - ferrofluids

can be formed by a magnetic field and are used in hydraulic suspension pistons - strength of the magnetic field allows the suspension to be hard or soft depending on what’s necessary. they also have friction reducing properties allowing magnetic objects to glide across the surface

smart materials - polymorph

a polymer that becomes malleable when heated to about 62°C. when it cools it becomes hard enough to drill & cut. this makes it perfect for modelling as it can be reheated & formed again. it’s also excellent for creating ergonomic handles

composite materials

made up of different materials combined to improve their properties. can be a combination of natural and synthetic materials

3 main categories: fibre-based, particle-based and sheet-based

like all modern materials composites are engineered to improve their properties. often the original material has a useful feature but lacks strength or durability. different material combinations can solve this problem. new composites are being developed all the time

fibre-based composites

composites reinforced with fibres. by mixing resin or concrete with fibres of glass or carbon you get the ability to mould complex shapes, but the reinforcement with fibres makes them very strong

glass-reinforced plastic (GRP) uses glass fibres & resin and is used in boat and instrument cases

carbon-reinforced plastic (CRP) uses carbon fibre & resin and is used in F1 car bodies, crash helmets & sports equipment

glass-reinforced concrete (GRC) uses glass fibre & concrete and is used in street furniture and urban features

particle-based composites

composites made with small particles of material. by mixing smaller parti les of sand with larger particles of cement & aggregate (fragments of rock / stone / pebbles) we get a very strong and dense material suitable for building large structures

concrete is made of cement, sand and aggregate and is used for buildings and street furniture

cermet is made of ceramic and metal and is used for electronic components that need to operate under very hot temperatures

sheet-based composites

often available in large sheets. by mixing wood fibres or thin slices of wood veneers with resin you can form large stable sheets for furniture panels and interior construction

medium-density fibreboard (MDF) is made of wood pulp and resin and is used for furniture and interior cladding

plywood is made of wood veneers and resin and is used for furniture and construction

clipboard is made of wood chip and resin and is used for furniture panels and construction

technical textiles

modern textiles can be engineered to have numerous properties like additional strength or resistance to fire, water or dirt

since the development of synthetic fibres there have been numerous improvements in textiles technology and new variations are constantly being produced. like other modern materials properties can be combined or enhanced to meet specific needs

technical textiles: polyamide/nylon

a major advance in textiles technology was the invention of polyamide or nylon, a synthetic material that can be pulled into very thin strands when heated and spun like natural textiles. it’s used extensively as a fabric in clothing

technical textiles: conductive fabrics

allow a small electric current to safely pass through them. used to dissipate static charge or for touch-screen gloves

technical textiles: fire-retardant fabrics

textiles that are more resistant to fire through chemical treatment or manufactured fireproof fibres. often used in furniture and furnishings where fire safety is important

technical textiles: kevlar

a tightly woven fabric that has great impact resistance. used in racing tyres, racing sails, gardening gloves and bulletproof vests

technical textiles: microfibres

much thinner than human hairs and can be coiled to provide a very warm, soft or absorbent material that can be used in winter clothes or products like cleaning cloths

technical textiles: microencapsulation

involves encapsulating liquid or solid substances in tiny thin-walled bubbles. these microspheres gradually release active agents when rubbed, which ruptures the thin-walled membrane. this can bring benefits like smelling good to cover body odours in sports clothing. a similar technology is used in scratch and sniff perfume and aftershave samples in magazines

types of motion

mechanical devices all have an input motion, which transforms the force to make an output motion

linear motion: moves something in a straight line eg a train moving down a track

rotary motion: something moves around an axis / pivot point eg a wheel

reciprocating motion: a repeated up & down or back & forth motion eg a piston or pump

oscillating motion: a curved backwards & forwards momentum that swings on an axis / pivot point eg a swing or clock pendulum

levers

use mechanical advantage to make lifting / applying pressure easier. all levers are made of a bar and a pivot called a fulcrum. 3 main parts:

• effort: the amount of force applied by the user, aka the input

• fulcrum: where the lever pivots

• load: the weight that needs to be moved, aka the output

mechanical advantage

the radio of force produced compared to force applied. the amount of help you get using a machine in comparison to doing something with just human effort. created by levers

measured by dividing the load by the effort (both measured in Newtons) - aka output / input:
mechanical advantage: load (N) ÷ effort (N)

the mechanical advantage can also be calculated theoretically by measuring the distance between the load & pivot and the pivot & effort

classes of lever

3 different types of levers, chosen for their ability to produce the most mechanical advantage for a particular task. arrange the effort, load & fulcrum in a different order

first order: effort, fulcrum, load

second order: effort, load, fulcrum

third order: fulcrum, effort, load

first order levers

place the fulcrum between the effort & load eg a seesaw

if the load is closer to the fulcrum it becomes easier to lift. when the fulcrum is in the centre the effort & load have to be equal to balance them

a crowbar is a first order lever that puts the load closer to the fulcrum, giving it more power to move a load. when the fulcrum is moved nearer the load it takes less effort to move it

second order levers

place the fulcrum at one end of the lever and the effort at the other with the load in the centre

the closer together the fulcrum & load are, the easier it is to lift the load

eg wheelbarrows, nutcrackers & bottle openers

third order levers

place the effort between the fulcrum & the load. if the effort & fulcrum are far apart it’s easier to lift

doesn’t have the mechanical advantage of the other order so is less common

generally used for moving small or delicate items eg tweezers or fishing rods

linkages

levers can be joined together to form linkages. simple ones change the direction of motion & the amount of force

reverse motion linkages

change the direction of input so the output goes the opposite way. a fixed pivot forces the change in direction. often used on foldable clothes horses

parallel motion or push/pull linkages

use 2 fixed pivots to make the input and output travel in the same direction through a link arm. each fixed pivot has a moving pivot on either side, allowing the movement & power to go backwards & forwards

changing the placing of the fixed pivots changes the amount of force exerted while keeping the direction the same

eg a toolbox with draws that open

bell crank linkages

change the direction of a force through 90°

amount of input force can be changed by moving the fixed pivot

used in bicycle brakes so the rider can pull the brakes from the handlebars and make the brake pads touch the wheels

crank and slider linkages

change rotary motion into reciprocating motion

a fixed pivot is attached to a crank which turns around and pushes & pulls a slider

when used in a car engine the ignition of petrol by the spark pushes the slider up, moving the connecting rod & turning the crank

treadle linkages

use a rotary input to turn a crank on a fixed point. a connecting rod joins 2 moving pivots to another fixed pivot

used for windscreen wipers in cars - move backwards & forwards together

angles in linkages - angle rules

a Z angle has 2 internal angles which will both be the same as long as the input & output linkages are parallel

where 2 lines intersect, the opposite angles are equal. where 2 angles sit on a horizontal line the total angle together is 180°

corresponding angles are the same in a F arrangement

cams & followers

a cam mechanism is the shaped part on a pivot point that converts reciprocating motion to rotary motion. has 2 main parts:

• a cam - attached to a crankshaft (a rotating shaft)

• a follower - touches the cam & follows the shape, moving up & down

types of cams

circular cams use an offf-centre pivot to cause the follower to move up & down. it will rise & fall by a reasonably large amount. can be seen in pistons eg on steam engines

pear cams remain stationary for half a turn then gently rises & falls. used to make carousel horses rise & fall

snail or drop cams look like a snail shell and cause the follower to stay stationary for half a turn before gently rising and suddenly falling. only work rotating in one direction. used on production lines to make regular holes / cuts in an item

heart-shaped or constant velocity cams make the follower rise & fall steadily with uniform velocity. no stationary period