Technology 9 November Flashcards
What is an Outline
All parts of the object that are visible
What is a Dimension line
These describe the size
What is a Hidden detail?
Parts of an object that is not visible
What is a Centre or long-link chain line
It indicates the centre of an object
What is a Projection line
Used to show the projection between different lines
What is a Construction line
Used while constructing the main drawing
Look at pg 3 of Graphic communication for images of lines
Learn table
What is a dimension
A dimension is the length of a part of a line, shape or object. These can either be one-dimensional, two-dimensional or three-dimensional.
What is a 1-dimensional line
A one-dimensional shape is simply a line. A line has a length but no thickness. The length of the line is the one dimension. A line is drawn with some thickness to enable us to see it.
What are the 4 types of lines
Curved
Verticle (up and down)
Oblique (diagonal)
Horizontal (left to right)
What are 2-dimensional shapes
These are flat shapes or surfaces that in most cases need at least two dimensions to fully describe them. The true shape of 2D surfaces, because they are flat, can be drawn on flat sheets of paper.
What is an orthographic drawing
It is when each plane of a 3D object is drawn seperatley
The following will show you where each drawing must go
Front view Side View
Top view
What 5 things does the design process consist of
1) Identify (needs or wants)
2) Investigate (needs analysis and description)
3) Design (designing, developing and making)
4) Evaluate (testing, evaluation and presentation)
5) Communication (the idea or solution)
What is a structure
A structure is an arrangement of materials intended to support, bear, contain or withstand applied loads and forces. We are surrounded by structures, both natural and manufactured.
What are the reasons for structures
Structures provide protection and shelter.
the shell of a snail
Structures support loads.
The spider’s web
Structures provide containment.
What are the 3 types of structures
Shell structures
Frame structures
Mass / Solid structures
What is a shell structure
A shell is a hollow structure, which could bear substantial loads, contain, support and protect something.
What is a frame structure
Frames are useful in structures where strength and lightness are essential.
What is a mass or solid structure
A mass or solid structure is made up almost entirely of matter.
In making decisions about the type of structure, materials and dimensions, there are three critical factors to consider. What are they
1) Strength
The structure must not fracture or collapse when in use.
2) Rigidity
The structure must resist bending, buckling, twisting or distorting in shape when loaded.
3) Stability
The structure must not fall over.
Define force
Force is an effect that a body experiences as something that pulls or pushes it
What is referred to when someone asks about the strength of a structure
The strength of a structure is the strength of the material from which it is made. This is the resistance of the material to fracture when force is applied to it.
What is a Newton
A Newton is the unit by which force is measured. It is abbreviated as N. A force of strength 1 Newton is approximately equal to the weight (the force of gravity) on a 100-gram mass.
What is a load
In Technology, a force applied to a body or a structure is called a load. When the body is subject to the force, it is loaded
What are the two types of loads
Static loads
These are loads that build up gradually over time, or with negligible dynamic effects. Since structural analysis for static loads is much simpler than for dynamic loads.
Dynamic loads
These are loads that display significant dynamic effects. Examples include impact loads, waves, wind gusts and strong earthquakes.
Define stress (in a structure)
The concentration of force over an area is called the stress in the material.
The following is a general rule for area and load
Load: the greater the load on an object, the greater will be the stress in the material.
Area: the smaller the cross-sectional area the greater will be the stress in the material.
NB: It is the stress in the material and not the load applied on an object, that determines whether it will fracture or not.
What are the types of stress
Material can be stressed in 4 ways:
1) Tensile stress causes tension in the material.
2) Compressive stress causes compression in the material
3) Shear stress
4) Torsion stress
What is the unit for stress
The Pascal (Pa) is a force of 1 Newton acting over an area of 1m² in a material.
Briefly explain the rigidity of structures
Not only must structures be strong enough to carry the load they must be rigid.
The rectangular wooden beam is strong enough to carry a load without braking but the load causes bending of the beam.
The simple way of making this rectangular profile beam rigid is to re-orientate it so that the longer edge is vertical
Making H-bars,T-bars or angle–iron makes metal beams more rigid
Scoring and folding a piece of card in corrugations makes a rigid beam
What are the 4 ways of strengthening a structure
1) Triangulation
Triangulation is to design and make the framework with the members joined to form triangles
2) Gussets
Gussets are plates that are attached at the joints of the framework.
3) Tie
The part of the structure that has a tensile force acting on it is called a TIE
4) Strut
The part that has a compressive force acting on it is called a STRUT.
Define the centre of gravity in an object/structure
The point, at which the pull of gravity (weight) acting to the left and to the right of a point is equal, is known as the centre of gravity of that object.
What is a bridge
Bridges are structures that support loads. They provide passage over some sort of obstacle: a river, a valley, a road or a set of railroad tracks.
Name the 4 types of bridges
There are four major types of bridges:
∙ the Beam bridge
∙ the Arch bridge
∙ the Suspension bridge
∙ the Cantilever bridge
What is the key difference between bridges
The biggest difference between these is the distance they can each cross in a single span. A modern beam bridge is likely to span a distance of up to 60m, while a modern arch can safely span up to 245 or 305m. A suspension bridge is capable of spanning up to 2000m.
What allows one type of bridge to span greater distances than another type of bridge?
What allows one type of bridge to span greater distances than another type of bridge lies in how each bridge type deals with two important forces called Compression and Tension.
Define Compression
Compression is a force that acts to compress or shorten the object it is acting on.
What is Tension
Tension is a force that acts to expand or lengthen the object it is acting on. A member of a frame that is being stretched is called a tie.
True or False Compression and tension are present in all bridges.
True
Compression and tension are present in all bridges. It is the job of the bridge design to handle these forces without buckling or snapping.
Define buckling
Buckling is what happens when the force of compression overcomes an object’s ability to resist compression.
Define snapping
Snapping is what happens when the force of tension overcomes an object’s ability to resist tension.
How does one deal with buckling and snapping
The best way to deal with these forces is to either dissipate them or transfer them.
Define the term dissipate
To dissipate force is to spread the force out over a greater area, so that no one spot has to withstand the worst of the concentrated force. An arch bridge is a good example of dissipation.
Define the term transfer
To transfer force is to move the force from an area of weakness to an area of strength that was designed to handle the force. A suspension bridge is a good example of transference.
What is the supporting lattice work to a beam bridge called
This supporting latticework to a beam bridge is called a truss
What is a beam bridge
A beam bridge is a rigid horizontal structure that is resting on two piers, one at each end. The piers directly support the weight of the bridge and any traffic on it. The weight is travelling directly downward.
How do beam bridges deal with tension and compression
The force of compression manifests itself on the topside of the bridge’s deck. This causes the upper portion of the deck to shorten. The result of this compression on the upper portion causes tension in the lower portion of the deck (fig.34). This tension causes the lower portion of the neck to lengthen.
Fig.34
Many beam bridges handle the load of compression and tension by increasing the height of the beam. By increasing the height with more concrete or steel beams, the beam has more material to dissipate the loads. This supporting latticework to a beam bridge is called a truss (fig.35 & 36). A support truss adds rigidity to the beam, greatly increasing its ability to dissipate compression and tension.
What is an arch bridge
Each span in an arch bridge is a beam supported by the very strong arch structure. An arch bridge is a semicircular structure with abutments on each end.
The force of compression is pushed outward along the curve of the arch (fig.37) towards the abutments.
Why is the tension in an arch bridge negligible
The tension in an arch is negligible. The natural ability of an arch to dissipate the force outward greatly reduces the effects of tension on the underside of the arch. The larger the semicircle of the arch however, the greater the effects of tension on the underside will be.
What is the job of the keystone
The keystone is the most important stone in an arch bridge, without this stone the arch would collapse. The keystone holds the arch together.
What is a good example of an arch bridge
The Sydney Harbour Bridge (fig.38 & 39) is a very famous example of an arch bridge. It is still the largest (but not the longest) steel arch bridge in the world.
Fig.38 Fig.39
Bloukrans Bridge in Garden Route
What is an aqueduct
Ancient Romans built arch bridges and aqueducts (fig.43) that are still standing and structurally sound today. These bridges and aqueducts are real testaments to the natural effects of an arch structure.
How do suspension bridges cope with compression and tension
Compression pushes down on the deck (fig.45), but because it is suspended, the cables transfer the compression to the towers, which dissipate the compression directly into the earth. The cables between the supports receive most of the tension forces. The anchorages are also under tension, but since they are also held firmly to the earth, the tension is dissipated into the earth.
Almost all suspension bridges have a supporting truss system beneath the deck. This helps to stiffen the deck and reduce the tendency of the roadway to sway or ripple.
What is a suspension bridge
A suspension bridge is one where cables (or ropes or chains) that are securely anchored are strung across an obstacle and the deck is attached or “suspended” from these cables. Most suspension bridges have two tall towers through which the cables are strung (fig.44). Thus, the towers are supporting the majority of the weight.
What are the 2 different types of suspension bridges
The classic suspension bridge is recognised by the elongated “M” shape (fig.45). ∙ The less common cable-stayed design, has more of an “A” shape (fig.46).
The longest bridge in the world is the Akashi Kaikyo Bridge (fig.48) in Japan.
How thick are the cables in a suspension bridge
The main steel cables are extremely thick. Each main cable is composed of smaller cables bound together to form an extremely strong single cable.
What is a cantilever bridge
A cantilever is one of the simpler beam structures. It is a beam that is supported at one end only and can carry a load along the length. It is very limited in its possibilities and is mainly used in drawbridges.
Give an example of a cantilever bridge
Scotland’s Forth Rail Bridge (fig.50)
Briefly explain the identify step of the design process
Knowing where and what the needs and wants of the community are. Analysing a specific scenario or situation and being able to draw out the opportunities to improve the specific situation, is where the whole process begins.
It is vital to continually be on the lookout for and identify potential obstacles, needs or wants throughout the Design Process.
Briefly explain the Investigate step in the design process
Analyse the situation and do research to gain information that will make the way forward easier.
Skills employed during this phase are collecting, information-processing skills, recording, identifying, analysing, questioning, predicting, communicating, comparing, observation, listening, classification, arranging, calculation, interpretation and collation.
What would one do research on when investigating
- The background context
- The environmental situation
- People concerned
- Comparing existing product
- Develop practical tests for your ideas
What are some questions that you can ask when researching
How? What? Where? When? Who? Why? What if? Etc. These questions are a handy tool that designers make use of and will help to streamline your research
Other questions such as
Time? Cost? Safety? Availability? Materials? Etc. Should also play a part in your mind map.
Why are mind maps important
A mind map is a great tool that can be employed to help with brainstorming and research.
What skills are needed when designing
Planning, drawing, sketching, calculating, testing, investigating, communication, illustrating, modelling, modifying, experimenting, considering, comparing, evaluating, choosing, accepting, rejecting, applying, use of colour, 2D & 3D drawings etc.
What is a design brief
A design brief is a short statement giving the specific outline of the problem, need, want or opportunity. Formulate the problem simply in or two sentences, clearly and comprehensibly. It should contain only the necessary information and be written in general, non-specific terms. Design briefs contain constraints and specifications. The design brief should not offer a solution; it should not indicate how to set about solving the problem, but the final goal should be stated clearly.
What are four key points to remember about your brief.
1) Identify the task you are keen to work on.
2) Make sure the brief has a purpose.
3) Do not begin with such a vague brief that you have no idea where to start.
4) Do not define the brief so precisely that there is no room for innovation or creativity.
What are constraints
Constraints outline the limits within which the work must be done. These will provide a more clear understanding of the design limits, which will affect what can ultimately be achieved. Constraints set limits but do not restrict you to one answer/solution only. A constraint should cover the full range in which a solution can be found. Leave your constraint open-ended to allow for a wide range of solutions.
Define specifications
Specifications outline specific details of the design of the product or system, which must be satisfied. A specification is much more detailed than the design brief that is selected. This is because a specification is a narrower description and definition of the brief.
What are some examples of constraints and specifications
∙ People: Age, target market, human rights, access
∙ Purpose: Function, what the product will do
∙ Appearance: Colour, Shape, Feel
∙ Environment:Where the product will be used, made,
impact on the environment in the long and short term
∙ Safety: For the users and the manufactures
∙ Cost: Of materials, wastage, manufacture, selling price
∙ Ergonomics
∙ Quality
∙ Production: Mass, batch or once-off production
How to develop a plan
Draw up an outline for the following:
∙ Resources needed (e.g. materials list, tools, people, cost)
∙ Sketches showing the necessary dimensions or quantities
∙ All the steps necessary to make the product
Choose and use appropriate tools
Change and adapt design using measuring and checking procedures
Use safe working practices
What often causes technological opportunities
In the real world, it is often the evaluating of existing products that prompts technological opportunities
What does testing the product do
The prototype of the design must now be tested to see if it solves the problem, need, want or opportunity outlined in the brief. Very few designs are perfect.
What are technical conventions
Technical Conventions:
These are the standardised language of symbols, line types, dimensions, units of measurement, South African drawing conventions etc.
What must be taken into consideration when designing for people
When designing for people, five main factors should be considered:
1. The size of the person using the object
2. The types of movement that person will make
3. The reaction of the body to the design through the senses
4. Human rights issues
5. The impact the design will have on the environment and society
What is Ergonomics
Ergonomics:
This is the study of the design of objects, for safe efficient interaction.
What are Aesthetics
Aesthetics
These qualities of the design are what make it attractive or a pleasing experience e.g. colour, shape, texture etc.
Aesthetics are experienced through our own senses.
What are the 5 types of gears
Spur Gear.
Chain and sprocket
Bevel Gear. …
Rack and pinion
Worm Gear.
What is a gear
A Gear is a disk with teeth around its edge
What is the function of an idler gear
If you want the gears to turn in the same direction, an IDLER gear is introduced to the system.
What are gears used for
Gears are mechanical devices that can be used to:
Trade speed for power
Translate motion from one axis to another
To gain mechanical advantage
1.1 To increase or decrease the speed of rotation
1.2 To increase or decrease the force of the rotation
2 To shift movement
2.1 To reverse the direction of rotation
2.2 To move rotational motion to a different axis
2.3 to keep the rotation of two axis synchronized
What is a Pulley
A pulley is a disk with a groove around its edge
Two types of pulleys
Fixed and moveable
What are the three types of levers
Class 1 Lever
The FULCRUM is in between the EFFORT and The LOAD
Class 2 Lever
The LOAD is in between the EFFORT and The FULCRUM
Class 3 Lever
The EFFORT is in between the FULCRUM and The LOAD
When the gears teeth are interlocked its called
When 2 or more gear wheels have their teeth locked we say they have meshed.
Define system
Systems help human beings to be in control of things around him/her and make work easier.
A System (Mechanism) is a device that changes an input motion or force into a desired output motion and force.
Name 4 gears, and give an example of how they are used in everyday life:
Rack and pinion: steering mechanism
Spur: Washing machines
Chain and sprocket: Bicycles
Bevel Gears: Power plants
Worm gear: adjustment systems for string instruments
