Design and Technology Notes

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dam is used to trap water, the water released turns turbines, turbines turn generators, electricity is distributed. Wind-blades are designed to catch wind, blades turn turbines using gears, turbines turn generators, electricity is distributed. Solar photovoltaic- photovoltaic cells convert light to electricity. Tidal barrages- barrage built across river estuary, turbines turn as tide enters (and when tide leaves), turbines turn generators, electricity is distributed. Wave-motion of waves forces air up cylinder to turn turbines, turbines turn generators, electricity is distributed. Geothermal- cold water is pumped underground through heated rocks, steam turns turbines, turbines turn generators, electricity is distributed. Biomass- fuel (wood, sugar cane, etc.) is burnt to generate heat, which heats water to generate steam; steam turns turbines; turbines turn generators; electricity is distributed. Switching to alternative and renewable fuel sources means the non-renewable fuel sources will last longer. Types of Motion- Basic Gears Rotary motion- Rotary motion follows the path of a circle, for example the rotation of wheels or an electric motor shaft. Rotary motion can be measured by counting the number of revolutions in a set period of time, for example revolutions per minute (RPM). Linear motion- Linear motion is in a straight line, for example a vehicle travelling in a straight line or items on a conveyor belt. The speed at which objects travel in a straight line is measured by dividing the distance they travel by the time taken (speed- distance/time). Speed is often measured in metres per second (m/s) or kilometre per hour (km/h). Oscillating motion- Oscillating motion is similar to circular motion, but the motion moves back and fourth in a circular path. An example is the head of an electric toothbrush. The rate of oscillating motion is measured in oscillations per second or per minute. Reciprocating motion- Reciprocating motion is back and fourth in a straight line. An example is the blade on an electric jigsaw. The rate of reciprocating motion is also measured in oscillations per second or per minute. A spur gear is a wheel with teeth around its edge. The teeth of a spur gear mesh with (link into) other gear spurs to form a gear train. A simple gear train consists of a driver gear (the input) and the driven gear (the output). If the driver gear is the smaller gear, it is called a pinion. Gears are mounted on shafts that carry the rotation to different parts of the mechanism. If the two gears in a simpler gear train are different sizes, they will rotate at different speeds. The simple rules are: The smaller gear will rotate faster than the larger gear. The gears will rotate in opposite directions. A gearbox is a mechanical system that contains several simple gear trains working together to achieve a very large speed reduction. Gear systems usually require some form of lubrication (a substance applied to reduce friction) to reduce friction (resistance caused by two surfaces rubbing together) and to prevent the teeth wearing away, for example oil or grease. Social and Ethical Issues- Including Overseas Production Fair trade- Fair trade is about establishing better prices, working conditions and terms of trade for farmers and workers. Many supermarkets and department stores stock fair trade goods, for example tea, coffee, chocolate and rice. Social and ethical awareness- Products are made by real people and there are moral implications for us all when buying things. We need to consider the social (social awareness- how the designing, making and use of products impact upon people) and ethical issues lethical awareness- concerned with doing the right thing) involved in designing and making the products we buy. For example, the cotton industry has a huge ethical issue surrounding child labour and the welfare of workers. People can make a difference by being aware of social and ethical issues and making informed choices when designing or buying products. For example, buying clothes made from fair trades cotton helps low-paid cotton farmers around the world. Ergonomics and Anthropometrics Ergonomics is the study of the relationship between people and the things they do, the objects they use, and their environment. A product that has been designed with ergonomics in mind is likely to be easier and more straightforward to use. What environment will it be used in? 1 Ergonomics How do people use it? What size, shape or weight should it be? Can people understand it? Anthropometrics are human body measurements (for example, height, weight, finger length, hand-span). Anthropometric data can be used by all designers to help to ensure a product is easy to use for all potential users. For example, anthropometric data can help designers to find the best height and width for a workstation. Fibres and Textiles Fibres can be mixed or blended together to benefit from the properties of more than one fibre- improving the function, aesthetic value or cost of the final product. Fibre Cotton Linen (flax) Wool Silk Natural fibres- Properties/working characteristics Absorbent, strong, good handle, cool to wear, drapes well, creases easily, easy to handle and sew, will not stretch, burns easily Absorbent, strong, good handle, cool to wear, drapes well, natural lustre (shine), creases easily, easy to handle and sew, will not stretch, burns easily Absorbent, strong, good handle, warm, crease resistant, shrinks easily, drapes well, difficult to handle and sew, stretches easily, some flame resistance Absorbent, strong, good handle, good insulator (cool in summer and warm in winter), drapes well, high natural lustre (shine), crease resistant, difficult to handle and sew, low stretch (can be stretched out of shape), burns slowly Uses Medical dressings, T-shirts, socks, denim jeans, cosmetic pads, nappies, bed sheets, upholstery, canvas, car tyre cords, fishing nets Bed sheets, table coverings, tents, skirts, suits, upholstery, canvas, wallpaper, bank notes Coats, jumpers, sportswear, blankets, socks, insulation, soundproofing, snooker tables, carpeting Evening wear, ties, handkerchiefs, bed sheets, medical dressings, parachutes, sutures (stitches), wall coverings Fibre Polyester Nylon (polyamide) Acrylic Viscose (rayon) Elastane Synthetic fibres- Properties/working characteristics Non-absorbent, strong, good handle, poor insulator, durable, crease resistant, will not stretch, melts easily Non-absorbent, abrasion resistant, very strong. some elasticity, durable, Resistant to chemicals and perspiration Water resistant, quick drying, strong, good insulator, resistant to chemicals and perspiration Absorbent, good insulator, creases easily, will not stretch, weak fibre, particularly when wet Non-absorbent, excellent. elasticity, resistant to chemicals and perspiration, quick drying Uses Clothing, pillow filling, upholstery padding, bedding, carpeting, thread, ropes, boat sails Seat belts, tents, parachutes, rucksacks, shoelaces, toothbrush bristles, umbrellas, life jackets, tights, underwear, carpeting Fleece, ski jackets, blankets, rugs, outdoor furniture, knitwear, cleaning cloths Blouses, sportswear, shirts, blankets, curtains, table cloths, upholstery Swimwear, sportswear, denim jeans, leggings, tights