Mocks Flashcards
1
Q
What is a mechanism?
A
- all mechanical systems have mechanisms which transform an input motion and force into an output one
- they’re designed so you can gain a mechanical advantage from using them (make something easier). This involves changing the magnitude and direction of the applied force
- some mechanisms change one type of motion into another
2
Q
What are the various types of motion?
A
- linear motion: moving one way in a straight line
- reciprocation motion: moving backwards and forwards in a straight line
- oscillation motion: moving backwards and forwards in an arc
- rotary motion: moving in a circle
3
Q
What are levers?
A
- levers move and lift loads by rotating about stationary points called fixed pivots
- there are 3 main types of lever that you need to know about: first order, second order, and third order
4
Q
What are first order levers?
A
- first order levers have the pivot between the effort and the load. Pushing down on your side of the lever lifts the load up the other end - the lever has rotated about the pivot
- if the load is closer to the pivot than the effort, a large load can be lifted using smaller effort - the lever gives a mechanical advantage
- as as you move the pivot closer to the load it becomes easier to lift - the magnitude of the effort required decreases
5
Q
What are second order levers?
A
- second order levers have the load in the middle
- here the pivot is at one end of the lever and the effort is at the other end. The classic example is a wheelbarrow.
- the closer together the pivot and load are, the easier it is to lift
6
Q
What are third order levers?
A
- third order levers have the effort in the middle
- third order levers can be things like fishing rods, cricket bats, and garden spades
- moving the effort and pivot further apart makes it easier to move or lift the load
7
Q
What are linkages?
A
- levers can be connected together to form linkages
- Simple linkages can change the magnitude of the force and the direction of motion
- two examples are: push/pull linkages, and bell cranks
8
Q
What are push/pull linkages?
A
- push/pull linkages use 2 fixed pivots
- the input and output motions of the linkage are in the same direction. The motion of the link arm is in the opposite direction
- Here, each fixed pivot is in the centre of an arm. Changing the position of these pivots will change the magnitude of the the output force - often the easiest way to see this is by making a model
9
Q
What is a bell crank/
A
- a bell crank changes the direction of a force through 90°
- the magnitude of the output force can be changed by moving the fixed pivot so it’s not an equal distance between the two moving pivots
10
Q
What are gears and gear trains?
A
- gears are toothed wheels that interlock. They transfer motion from one part of a machine to another
- a gear train is where two or more gears are linked together. They can be used to change the direction of motion or change the magnitude of the input force
- e.g. in a driver gear, turned by hand or a motor, turns the driven gear. Both will turn the opposite directions.
- e.g. if you use a third gear (called an idler) the driver and driven gears will move in the same direction. The idler does not affect the speed of the other two gears.
11
Q
How can the relationship between the driver and driven gears be described?
A
- if linked gears are different sizes, the smaller gear will turn faster
- this relationship can be shown by using a gear ratio
- gear Ratio = no. Teeth on driven gear /no. Teeth on the driver gear
- the size of this ratio describes how much the mechanism changes the speed of the gears from the input speed to the output speed
- output speed = speed of driver gear (input speed) / gear ratio
12
Q
What are rotary systems?
A
- mechanical systems that work by using rotary motion (e.g. gear trains)
13
Q
What is a pulley?
A
- a simple pulley is made up of a wheel with a grooved outer edge and a cable, rope or belt that sits on the groove
- pulleys make lifting a load easier
- one pulley on its own changes the direction of the force required. The same amount of force is needed but pulling down might be easier than lifting something up
- using two or more pulleys together can change the magnitude of the force too - they can make things feel a lot lighter
- e.g. one fixed pulley and one moving pulley (a block and tackle) will mean you only need half the force to lift a load
14
Q
What is a belt drive?
A
- a belt drive transfers movement from one rotating shaft to another
- belt drives are used in pillar drills and washing machines
- in a pillar drill, a flexible belt joins two separate pulley wheels - this links the motor to the drill shaft
- this belt can be put in different positions to make the drill turn faster or slower. This works in a similar way to gears - if the wheels are different sizes, the smaller wheel will spin faster
- the diameter of the wheel can be used to calculate the velocity ratio - how fast the driven wheel will spin relative to the driver wheel
- velocity ratio = diameter of the driven pulley wheel / diameter of the driver pulley
- output speed = speed of driver pulley wheel / velocity ratio
15
Q
What is a cam mechanism?
A
- cams change rotary motion to reciprocating motion
- it has two main parts - the cam and the follower
- cams come in many shapes and sizes but they always rotate
- changing the size or shape of the cam can be used to change the magnitude of the output motion (the reciprocating motion of the follower)
- the follower rests on the cam as it rotates and follows its shape. It may have a small wheel to reduce friction. The follower moves up and down (reciprocating motion) as the cam turns
16
Q
What are the different types of cams?
A
- circular cam: (offset or eccentric) produces a uniform reciprocating motion
- snail cam: for half the follower will not move, then it will gently rise and then suddenly drop. It will only work in one direction
- four-lobed cam: has four lobes (bits that stick out). For each turn of the cam the follower will rise and suddenly fall four times. This cam shape will only work in one direction
- pear cam: for half a turn the follower will not move then it will gently rise and fall
17
Q
Describe cartridge paper
A
- high quality and has textured surface
- great for sketching with different drawing materials like pencils, crayons and inks
18
Q
Describe Lay-out paper
A
- thin and translucent
- used for general design work
19
Q
Describe tracing paper
A
- semi transparent
- used to copy images
20
Q
Describe grid paper
A
- square or isometric pattern printed on it
- useful for orthographic and scale drawings
- isometric paper’s good for isometric drawings
21
Q
Describe bleed proof paper
A
- used when drawing with felt tips and marker pens
- ink doesn’t spread out/bleed
22
Q
What are boards
A
- the weight of paper and board is measured in gsm. Above 200 gsm it’s not paper anymore - it’s a board
- it’s often used in packaging because of its low cost compared to other packaging materials, and it’s high strength to weight ratio
23
Q
Describe solid white board
A
- high quality bleached surface, ideal for printing
- used for primary packaging
24
Q
Describe ink jet card
A
- used for ink jet printing
- designed so that ink doesn’t bleed
- allows printed image to be sharply defined and of a high quality
25
Describe corrugated card
- made up of a fluted inner core sandwiched between 2 outer layers which can be printed on
- the flutes add strength and rigidity
- this is useful in a lot of secondary packaging to protect products during transit
26
Describe duplex board
- has different colour and texture on each side
- often where only one side is seen, so that only one side needs to be smooth for printing
- used for food packaging
27
Describe foam core board
- is made by sandwiching expanded polystyrene foam between 2 thin layers of card
- it’s stiff, lightweight, and the thin outer card layer can be scored
- good for making models and mounting posters
28
Describe foil lined board
- has an aluminium foil lining
| - used for food packaging, foil keeps flavour in, and air and moisture out
29
What are softwoods
- grow in colder climates and fast
- cheap and accessible
- have leaves like needles and usually evergreen and have cones
30
Describe pine
- yellow with brown streaks
- string and cheap but knotty (harder to work with)
- used for telegraph poles, fences, and cheap furniture
31
Describe larch
- softwood
- attractive yellow to reddish-brown colour
- harder, tougher, more durable than most softwoods
- resistent to rot
- Good for decking and cladding the outside of buildings and fence posts
32
Describe spruce
- reddish brown colour
- hard and has a good strength to weight ratio
- knotty and not very durable
- used for structural purposes like air rafts, crates, and ship masts
33
What are hardwoods?
- grow in warm climates and slowly
- more expensive
- broad flat leaves and deciduous
- tighter grain and denser and harder (except balsa)
34
Describe oak
- light brown
- tough durable and very strong
- attractive grain markings
- finishes well
- used in interior panelling, flooring and furniture
- corrodes steel and fittings
35
Describe mahogany
- red-brown colour
- durable and easy to work with
- expensive
- good quality furniture
36
Describe balsa
- white or tan colour
- very low density for a hardwood
- very soft
- easy to cut and shape
- high strength to weight ratio
- modelling
37
Describe beech
- pinkish brown
- hard enough to resist denting
- can be bent using steam
- chairs and toys
38
Describe ash
- pale cream colour
- tough and absorbs shock well
- tool handles, wooden sports equipment
- attractive
- furniture
39
What are ferrous metals ?
- contain iron
- mostly magnetic
- protective coatings are often applied to prevent ferrous metals from rusting (except stainless steel as its resistent to rust)
40
Describe cast iron
Ferrous metal
Very strong is compressed but brittle and not malleable
Used for bench vices, car brake disks, manhole covers
41
Describe low carbon steel
Quite strong and cheap
Rusts easily and can’t be hardened
Used in car bodies, screws, nuts, bolts, nails, washing machines
42
Describe high carbon steel
Harder than low carbon steel
Can be hardened
Not as easy to work with and it rusts
Used in tools (e.g. chisels, files, saws, drills)
43
What are non-ferrous metals?
Don’t contain iron
So don’t rust and likely to be exposed to moisture
44
Describe Aluminium
Lightweight
Corrosion resistant
Expensive
Not as strong as steel and hard to join
Uses in aeroplanes, cans and ladders
45
Describe brass
Quite strong
Corrosion resistant
Malleable
Ductile
Looks nice
Used in electric parts, door handles and taps
46
Describe copper
Relatively soft
Malleable
Ductile
Very good electrical conductor
47
Describe tin
Soft
Corrosion resistant
Malleable
Ductile
Low melting point
Used in foil, tin cans, alloying metal in solder
48
Describe zinc
Not very string
Corrosion resistant
Used in coating steel (e.g. on nails, buckets and watering cans)
49
What are alloys?
One or more elements combined with a metal
50
Give example of 2 alloys and describe them
- high speed steel
Contains iron, mor Ethan 0.6% carbon and other metals u]including chromium, tungsten, and vanadium
It keeps its hardness when heated to high temperatures, so it’s used in high speed cutting tools that get hot when used
- stainless steel (iron and chromium and carbon and nickel)
Cast iron and mild steel are strong but rust easily
Adding chromium and nickel increases strength, toughness, and ductility and decreases rust
Used in surgical equipment, sinks and cutlery
51
What are the 2 types of plastics/polymers
Thermoforming
Thermosetting
52
What are thermoforming plastics?
- they don’t resist heat well and are easily formed into different shapes by heating, melting, and remoulding
- they are easy to recycle - they’re ground down, melted and re-used
53
Describe acrylic
Thermoforming
Hard
Stiff
Shiny
Resists weather well
Can be used to make motorcycle helmet visors, baths, signs
Is brittle
54
Describe high density polythene
Thermoforming
Stiff
String
Lightweight
Used for washing up bowls, baskets, folding chairs, gas and water pipes
55
Describe polythene terephthalate
Thermoforming
PET is a polyester
Light
Strong
Tough
Used to make see-through drink bottles and fibre for clothes
56
Describe high impact polystyrene
Thermoforming
Rigid and fairly cheap
Used for vacuum forming and fabricating boxes like CD cases or smoke detector casings
57
Describe polyvinyl chloride
Thermoforming
Brittle
Cheap
Durable
Used for blister packs, window frames, vinyl records and some clothing
58
Describe polypropylene
Thermoforming
Tough
Flexible
Can be made in a variety of bright colours
Used for plastic chairs
59
What are thermosetting plastics?
Plastics that resist heat and fire
Undergo a chemical change when heated and moulded to make a product - they permanently become hard and rigid
They’re non-recyclables
60
Describe epoxy resin
Thermosetting
Rigid
Durable
Corrosion resistant
Good electrical insulator
Used for circuit boards and wind turbine rotor blades
61
Describe urea formaldehyde
Thermosetting
Hard
Brittle
Good electrical insulator
Used for plus sockets and cupboard handles
62
Describe melamine formaldehyde
Thermosetting
Strong
Scratch resistent
Used to laminate chipboard and for plates and bowls
63
Describe phenol formaldehyde
Thermosetting
Hard
Heat resistant
Very easily moulded
Used for bottle caps And snooker balls
Also mic=send with other materials to form a composite
64
Describe polyester resin
Thermosetting
Hard
Stiff
Cheap
Good electrical insulator
Added to glass fibres to form glass-reinforced plastic
Used for kayaks, shower stalls and garden furniture
65
What are prototypes?
Prototypes are full-size, fully-functioning products or system
They’re made using the materials and manufacturing methods that are intended for the final product
This allows you to test the product and the production method you’re going to use
66
How does prototypes help?
Allows you to check that the manufacturing specification is correct
Any problem identified during this process will need to be solved, and the manufacturing specification modified to include the changes
Can help calculate manufacturing costs - important so you don’t end up with a final product that costs far too much to make (including materials, labour, packaging, cost of new equipment, energy and waste disposal
67
How can you use prototypes to evaluate you design?
Prototypes are evaluated by checking that they meet the criteria set out in the design specification
Parts that don’t fit the design specification can be improved
Need to make sure that the prototype meets the requirement of the design brief - what the client wants or needs
68
How does feedback from other people help?
- prototypes allow other people to try your product
- feedback from the client, potential customers and experts in the industry provide additional suggestions on how you can can modify your design
- this will improve the product so that it’s marketable - appealing to the target market, is fit for purpose and will sell
69
What is iterative design?
Modifying something, evaluating it, then making another modification and testing a that and so on (repetitive process)
70
What is modelling?
A practice version of your design or parts of it. It’s a good way to visualise your design in 3D and to spot any problems
The modelling stage should be used to try different materials and joining techniques, and considering reducing the number of parts to make construction easier
You can make models using materials that are easy and quick to work with (e,g, cardboard, balsa, jelutong, newspaper or foam core board
You can also use construction kits
You can use toile, breadboards, CAD/CAM, mathematical modelling
71
What is toile?
They are early versions of a clothing design. They can be worn by a model or put on a mannequin ad are used to work out proportions and fit the garment. Toiles for one-off garments are often fittend to the intended wearer
The fabric used should be cheap (so the design can be experimented and improved without costing too much and wasting the real fabric), lightly coloured (so you can mark up any changes needed) and have similar properties to the fabric your planning to use (to make the drape of the garment can be perfected too, as it will be similar to when the real fabric is used)
Calico is a common toile fabric
72
What are breadboards?
Used to test whether circuit design works
Boards with rows of holes that electronic components can be pushed through. Wires are plugged into other holes to complete the circuit for testing
Useful as they don’t require soldering - important when developing a circuit, as components can be easily removed and circuit easily changed
73
What is mathematical modelling?
- it shows how an object or system will behave in reality. These models are made using data and information about known relationships between variables
74
What are natural fibres?
Natural fibres can be harvested from plants and animals
Renewable resources and biodegradable and therefore sustainable
In general they are absorbent and strong when dry but have poor resistance to biological damage (e,g. from moths and mould)
75
Describe cotton
Natural fibre
Smooth
String, hard wearing, absorbent, comfortable to wear, feels quite cool in hot weather, easy to wash & add colour, doesn’t cause allergies, non-static, fairly cheap
Creases easily, high flammability, poor elasticity, can shrink when washed, dries slowly
Used in these fabrics; denim, corduroy, calico
Used in jeans, t shirts, blouses, soft furnishings
76
Describe wool
Natural fibre
Soft or coarse
Warm, absorbent, good elasticity, low flammability, crease-resistant, available in lots of fabric weights
Can shrink when washed, dries slowly, can feel itchy, fairly expensive
Used in fabrics: knitted fabrics, Harris tweed, gabardine, jersey, felt
Used in suits, jumpers, coats, dresses carpets
77
Describe silk
Natural fibre
Very smooth and glossy
Smooth, resistent to shrinking/stretching, absorbent, good drape, low flammability, comfortable to wear, lightweight , sun resistent
Creases easily, might not wash well, weak when wet, expensive
Used in fabrics: organza, chiffon, satin
Used in lingerie, underwear, dresses, shirts and ties
78
What are synthetic fibres?
Made from polymers (long chain molecules). These molecules come mainly from coal and oil - non-renewable fossil fuels. They are less sustainable than natural fibres
In general they are resistent to biological damage, can be changed to heating to form different shapes and textures. They are not very absorbent so they can be hard to dye
79
Describe elastane
Synthetic fibre
Soft
Extremely elastic, string, hard-wearing, lightweight, keeps its shape well, resists biological damage
Not absorbent, high flammability, not biodegradable
Used in LYCRA fabrics
Used in sportswear, underwear, combined with other fibres to add stretch
80
Describe polyester
Synthetic fibre
Smooth can have many different finishes
String, hard-wearing, low flammability, good elasticity, cheap, resists creasing, dries quickly, resists biological damage
Not absorbent, not biodegradable, damaged by string acids, melts as it burns
Used in DACRON fabrics
Used in sportswear, bed sheets, curtains, padding, tablecloths
81
Describe polyamide
Synthetic fibre
Can have many different finishes
String, hard wearing, warm, good elasticity, crease resistent, resists biological damage, fairly cheap
Not very absorbent, damaged by sunlight, melts as it burns
Used in nylon fabric
Used in sportswear, socks, tights, furnishings, carpets
82
How are fabrics made?
Yarns are Thread that are woven or knitted to make fabrics
Yarns are made of tiny fibres. These either come in short lengths (staple fibres) or longer lengths (filaments). Yarns f]made from filaments are smooth, whilst yarns made of stable fibres tend to be hairier
Filaments can be spun or used as they are. Staple fibres are spun to produce yarn
Yarns are available in different thicknesses. 1-ply yarn is a single yarn, 2-ply yarn is two yarns twisted together and so on…
There are three main ways to turn fibres/yarns into a fabric - they are weaving, knitting and bonding
Woven fabrics: are made by interlacing two sets of yarn
Knitted fabrics: are made by interlocking one or more yarns together using loops. The loops trap air, so they insulate. They stretch more than woven fabrics
Non-woven fabrics: layers of fibres held together by bonding or felting. They don’t fray and can be cut in any direction, which means there’s little waste when laying out patterns. However they don’t stretch and aren’t very strong
83
Describe woven yarn
Interlacing two sets of yarn - the weft (which goes from right to left) and the warp (up and down)
Simplest weave is the plain weave - the weft oases over and under alternate warp yarns , making it unpatterned. It’s hard wearing - string and holds its shape well and has a smooth finish. It’s the cheapest weave and is used to make loads of fabrics (especially cotton based ones)
Are woven using looms. Smaller looms are hand operated, but industrial looms are used to produce woven yarns in a large scale. They are computer operated and faster, meaning that fabrics can be mass produced at high speed
Used in shirts, upholstery, trousers
84
Describe knitted yarns
Two main types: weft-knitted and warp-knitted
- Weft knitted:
Yarn runs across the fabric, making interlocking loops with the row of yarn beneath
Stretch and can lose their shape easily
If yarn breaks, it can unravel and make a ‘ladder’
Weft-knit fabrics can be produced by hand or machine
Used for jumpers, socks and t shirts
-warp-knitted:
Yarn runs up the fabric, in loops which interlock vertically
They’re starchy but keep their shape
Fabrics are hard to unravel and are less likely to ladder
They’re made by machines (expensive)
Used in tights, swimwear, fleeces and some bed sheets
85
Describe non-woven fabrics
-bonded fabrics:
Webs of synthetic fibre that are glued, needle-punched, stitched, or melted together
Used for interfacing artificial leathers and disposable cloths
-felted fabrics:
Felt is made by combining pressure, moisture, heat to interlock a mat of wool fibres
Felt can be used for carpet underlay, craft material, hats, jewellery and snooker table coverings
86
What is manufactured board?
Processed pieces of wood glued and compressed into panels
87
Describe MDF
Manufactured board
Made from tiny fibres or softwood timber held together by glue ]
No natural grain
Cheap, dense, smooth uniform surface that takes paint and other finishes well. However it’s porous so can be damaged by moisture
Used for shelves and flat-pack-furniture
88
Describe plywood
Manufactured board
Made up of several layers of softwood or hardwood glued together with their grain at right angles to one another
That structur makes it very strong for its weight and thickness
Used for building and furniture
89
Describe chipboard
Manufactured board
Made by compressing wood chips, shavings and sawdust together with glue. Usually used with a veneered surface.
Cheap, not very strong, absorbent, can be easily damaged by moisture
Often used in cheap self-assembly furniture
90
What are the different types of forces?
Tension
Compression
Shear
Bending
Torsion
