GCSE (Edexcel) DT

Jelutong

hardwood - even and close grain (easy to shape) / soft and weak (not structural).

Used in: model making and as vacuum form moulds.

Birch

hardwood - Even and regular grain and is easy to work / not very resistant to rot and insects.

Used in: veneers (plywood and cheaper furniture finishes).

Ash

Hardwood - Strong and flexible, good for finishing / not very resistant to rot and insects.

Used in: tool handles, sports equipment, and ladders.

Oak

Hardwood - strong and durable, attractive grain / expensive, rare, hard to work, corrodes Iron and steel.

Used in: Structural building, high end furniture, wine barrels.

Mahogany

Hardwood - very attractive finish, easy to work / expensive, environmental problems with sourcing, is an allergen.

Used in: Furniture and as veneers

Beech

Hardwood - hard, does not easily crack or splinter / expensive, not weather resistant.

Used in: cooking implements, toys, and solid and laminated furniture.

Balsa

Hardwood - very light weight, easily cut/ very soft and structurally weak

Used in: model planes, surfboard cores, and old rafts.

Pine

Softwood - Pale-creamy colour, visible grain. / Contains lots of knots.

Cedar

Softwood - strong smell to keep away insects and weather resistant.

Larch

Softwood - Tough, water resistant, used in small boats. / Expensive.

MDF (Medium Density Fiberboard)

Manmade - No grain structure, very easy to work, made from off-cuts of scrap wood (very cheap). / disintegrates in moisture.

Plywood

Manmade - Thin layers glued together [flexible] (thin). Used in laminates.

Chipboard

Manmade - large chips glued together, made from off-cuts of scrap wood.

Knots

The cross section of a branch in the wood. Change in grain makes sawing harder. Resin in knots stains paint surfaces.

Colour

Varies between specific trees. Is different in every plank. Different woods have different colours, from the pale colours of pine to the rich, dark reddish browns of mahogany.

Elasticity

Measure of ability the stretch and warp. Wood has little. Most elastic is yew, so is used in bows.

Tensile Strength

The amount of pulling force a material can stand. In timbers in is 3-4x the compressive strength (amount of crushing force).

Social footprint

Logging can harm habitats of many animals. Timber is bio-degradable. Trend forecasting can help to predict what woods need to be grown.

Ecological footprint

Soft woods are more sustainable. Forest stewardship council (FSC) logo is used with wood from sustainable forests.

Linear

one direction, straight.

Rotary

one direction, around a central point.

Oscillating

Motion that swings backwards and forwards in an arc from a central point.

Reciprocating

Moving backwards and forwards in a straight line.

Class 1

L.F.E Large input movement can produce a small output movement but with greater force e.g pliers, crowbar

Class 2

E.L.F Large input movement can produce a small output movement but with greater force but the fulcrum is at one end e.g wheelbarrow, nutcracker

Class 3

L.E.F The force applied by the user is grater then the output force e.g tweezers

pear-shaped

Takes half the rotation to rise and fall.

eccentric

Smooth and continuous rise and fall. Pin is off-centre.

snail/drop

Gives a smooth rise and very quick sudden drop.

flat

Large SA means a higher max load at the cost of more friction.

knife's-edge

Used to precisely follow cam, wears down quickly.

roller

Used to reduce friction for higher speeds.

Single throw switch

Either on or off. Mechanical. Often used as a power or selector switch.

PTM/PTB switch (push to make/push to break)

On/off when pushed, other wise off/on.

LDR (Light Dependent Resistor)

A type of resistor where the variable for change is light intensity. More light = less resistance.

Thermistor

A type of resistor where the variable of change is temperature. When temperature is high resistance is low.

Resistor (fixed/variable)

Fixed = used to protect delicate components. Variable = can use an input to easily change resistance.

Transistor

Used to make a decision in a control device. Turns outputs on and off.

Mild steel

Ferrous - Most common metal, ductile, tough, fairly malleable. / Poor corrosion resistance.

Cast iron

Ferrous - Naturally non-stick, will not crack easily like the other two.

Stainless steel

Ferrous - Mild steel + other metals (chromium or nickel). Same as mild steel but is corrosion resistant.

Brass

Non-ferrous - 65/35 % copper/zinc, very hard, work hardened, oxidizes green.

Copper

Non-ferrous - Very soft, ductile, work hardened, easy to shape, excellent, can be annealed.

Aluminium

Non-ferrous - easy to form, light, common.

Ductility

Ability to bend/stretch/deform/twist. Ability to be drawn out without breaking. Increases with temperature.

Malleability

The ability for a material to be permanently deformed without fracturing. Increases with temperature.

Hardness

The ability to withstand deformation.

Fabrication

used to make parts of something.

Assembly

putting the parts together.

Redistribution

casting or moulding materials in one piece.