Technology

What is Technology and the Design Process

Technology is defined as the process of utilizing natural and synthetic materials to create new products that solve specific problems. This process is structured through a sequence of steps known as the Design Process.

The Steps of the Design Process

Identifying the Problem: Read the provided information regarding a problem and write a short explanation of it in your own words. * Example: Regan Sunglasses needs a design for beach sunglasses for students aged 16 to 21.
Researching how to Solve the Problem: Find out everything possible about the product being designed. Research areas include: * Availability of existing products that solve similar problems. * Optimal size and shape for the product. * Forces the product must endure. * Materials and tools needed for construction. * Total cost of the product. * Example Research Topics: Styles students prefer, typical spending habits, color preferences, and functional differences between beach and normal sunglasses.
Designing a Solution: This involves creating a Design Brief, which consists of two parts: * The Information Paragraph: Answers "What are you designing?", "Who asked for the design?", "Who is the user?", and "What is the purpose?" * Specifications and Constraints: * Specifications: A list of everything that must be done (e.g., "the sunglasses must be blue"). There is no choice left. * Constraints: A list of things that limit the design but still allow some choice (e.g., "must be a bright color," "must cost no more than $R500$ "). * Initial Design Drawings: Designers must produce at least two possible design solutions through sketches, including detailed notes to explain components. * Lists of Materials and Tools: An exhaustive list of every item needed, including adhesives (glue).
Making a Prototype: * Develop a final design with detailed plans. * Decide on a building plan (the sequence of construction). * Build a test model (prototype) to evaluate the design physically.
Evaluating the Solution: Testing if the solution solves the problem optimally. Evaluation should occur at every step of the process. The most critical evaluation happens once the prototype is finished but before it is presented to the customer.
Communicating the Solution: Presenting the final design and all related information to the client.

Factors Influencing the Design Process

Three constant factors must be evaluated at every stage:

Environment: The effect the design may have on the surroundings.
Community: How the design might affect different communities in the country (positively or negatively).
Bias: Ensuring the design is not biased toward one or more groups of people.

Graphic Communication and Drawing

Graphics are used to convey ideas without words. This includes everyday icons, road signs, and technical drawings.

Types of Lines in Working Drawings

Dark (Continuous): Used for completed drawings and to indicate visible edges.
Feint (Construction lines): Used as a guide for the drawing.
Dashed: Shows hidden details such as internal holes.
Wavy: Used to show part sections of irregular borders.
Chain: Indicated the center of a circular object or a hole for symmetry.

Artistic and Working Drawings

Freehand Sketches: Quick pencils drawings produced with only a pencil and eraser. Lines should be continuous and objects must be in good proportion.
Enhanced Drawings: Use texture, shading, shadows, and color to make a product look realistic.
Two-Point Perspective: A 3D drawing where the object "vanishes" toward two points ( $Lvp$ and $Rvp$ ) to create a realistic illusion of depth.
Isometric Drawing: A 3D drawing drawn on a $30^{\circ}$ horizontal axis.
Orthographic Projection: Standardized working drawings showing different views of an object.

Dimensioning and Scale

Dimensioning Rule: * Extension line: Drawn $1\,mm$ from the drawing edge. * Dimension line: Drawn the length of the piece being measured, at least $10\,mm$ from the drawing edge. * Arrows: About $3\,mm$ long and $1\,mm$ wide. * Dimension: A number written without units (units are understood to be in $mm$ ), placed $1\,mm$ above the dimension line. * Circles: Dimensioned using a diameter symbol ( $\varnothing$ ) or radius ( $R$ ). Extension lines are not used for circles.
Scale: Shown as a ratio of drawing size to actual object size. * $1:1$ : Same size. * $2:1$ : Drawing is twice the size of the actual object ( $2 \times$ size). * $1:2$ : Drawing is half the size of the actual object.

Forces and Materials

Force Definition and Measurement

A force is either a push or a pull on an object. It can result in movement, twisting, or the breaking of an object. Force is measured in newtons ( $N$ ), named after Sir Isaac Newton.

$Weight = Mass \times 9.8$

Example: An object with a mass of $10\,kg$ has a weight of $10 \times 9.8 = 98\,N$ .

Static Force: Does not move or change in strength (e.g., a brick resting on a surface).
Dynamic Force: Moves or changes in strength (e.g., force exerted on a skateboard).
Even Load: Centered perfectly on its support.
Uneven Load: Shifted to the left or right of its support.

Types of Forces

Compression: Pushing, squeezing, or crushing forces.
Tension: Pulling or stretching forces (an object is said to be "in tension").
Torsion: Twisting forces acting in opposite directions causing rotation. Internal cross-bracing is used to counteract torsion in structures.
Shearing: Two forces pushing in opposite directions on a part causing it to tear/shear (e.g., tearing paper).
Bending: The result of force pushing on a material. Bending subjects one side of the material to compression and the opposite side to tension. * Beams used to avoid bending: Flat bar on edge, Angle iron, T-bar, and I-beam.

Properties of Construction Materials

Density: Amount of matter compacted in a fixed volume ( $Density = \frac{mass}{volume}$ ). High density materials (like iron) are heavy; low density materials (like aluminum or foam rubber) are lighter.
Stiffness: Capability to resist bending (e.g., cast iron is stiff; iron wire bends easily).
Flexibility: Capability to bend and return to original shape without permanent distortion (e.g., spring steel).
Toughness: Capability to withstand sudden impact or shock (e.g., ash wood used for cricket stumps).
Brittleness: Material that cracks or breaks under compression rather than bending (e.g., concrete, glass, chalk).
Corrosion Resistance: Capability to withstand environmental breakdown. Stainless steel (iron mixed with chromium) resists rust. Wood is painted to prevent rot.
Stability: Capability to resist change in shape or size under varying conditions (wet, dry, hot, cold). Wood expands when wet; metal expands when hot.
Fatigue: Structural failure caused by materials being bent, stretched, or stressed too often.

Mechanical Systems: Gears

A gear is a wheel with wedge-shaped teeth. When the teeth of two adjacent gears fit together, they are said to "mesh."

Gear Types

Spur Gears: Most common. Used to change speed of rotation, transfer counter-rotation, or serve as force multipliers. Counter-rotation means meshed gears always turn in opposite directions.
Rack and Pinion: Converts rotary motion into linear motion (or vice-versa). Found in car steering, microscope focusing, and sliding gates.
Worm and Worm Wheel: A shaft with a screw thread (worm) meshing with a gear (worm wheel). The worm always drives the wheel. One revolution of the worm moves the wheel by one tooth, resulting in a large speed decrease but a massive force increase. Used in guitars and microscopes.
Bevel Gears: Teeth are cone-shaped, allowing rotation to be converted from one axis to another (usually at a $90^{\circ}$ angle).

Gear Principles and Ratios

Driver Gear: The gear to which power/force is applied.
Driven Gear (Follower): The gear turned by the driver.
Idler Gear: Placed between driver and driven gears to make them rotate in the same direction.
Velocity Ratio (VR): Relationship between the speed of the driven gear and driver gear. * $VR = \frac{\text{Driven teeth}}{\text{Driver teeth}}$ * $VR = \frac{\text{Driven diameter}}{\text{Driver diameter}}$ * If VR > 1, the driven gear turns slower. If VR < 1, it turns faster.
Force (Torque) Ratio: Relationship between the force of the driven and driver gears. * $Force Ratio = \frac{\text{Driver teeth}}{\text{Driven teeth}}$ * $Force Ratio = \frac{\text{Driver diameter}}{\text{Driven diameter}}$
Mechanical Advantage Laws: * The larger the gear, the slower it turns but the greater the force it exerts. * The smaller the gear, the faster it turns but the less force it exerts. * Velocity and Force ratios are indirectly proportional: as one increases, the other decreases. * Force multiplication occurs only when VR < 1 and Force Ratio > 1.

Mechanical Systems: Pulleys

A pulley is a grooved wheel for a rope or cable.

Pulley Types

Single Wheel Fixed Pulley: Redirection of force only ( $MA = 1$ ). It is easier to pull down (using one's own weight) to lift an object up.
Single Wheel Moveable Pulley: Attached to the load. Provides an $MA = 2$ because two lengths of rope support the load.
Compound Pulley (Block-and-Tackle): Two or more pulleys working together. Used for very heavy loads in cranes or engine hoists.
Belt-Driven Pulleys: Transmit rotary motion via a belt. Unlike gears, they rotate in the same direction unless the belt is crossed.

Pulley Calculations

Mechanical Advantage (MA): * $MA = \frac{\text{Weight of load (N)}}{\text{Effort (N)}}$ * $MA = \text{Number of falls (rope lengths supporting the load)}$
Rope Length and MA: * $MA = \frac{\text{Rope length pulled}}{\text{Height load lifted}}$ * If you gain force ( $MA = 2$ ), you lose distance (must pull double the rope length).
Velocity and Force Ratios (Belt Pulleys): * $VR = \frac{\text{Driven diameter}}{\text{Driver diameter}}$ * $Force Ratio = \frac{\text{Driver diameter}}{\text{Driven diameter}}$

Hydraulic and Pneumatic Systems

These systems use fluids to transfer force. A "Process" in these systems involves liquid or air flow to produce an "Output."

Core Principles

Pneumatics: Uses compressed air or gas. * Advantages: Cheap, easy to fix, clean (not messy), safe. * Disadvantages: Noisy, lacks accuracy.
Hydraulics: Uses liquid (usually oil). * Advantages: Accurate, provides constant force, copes with high pressure, oil acts as a lubricant and prevents rust. * Disadvantages: Expensive, messy, fire hazard, leaks are hard to block.
Pressure: Force spread over an area ( $P = \frac{F}{A}$ ). Units are $N/m^2$ or Pascals ( $Pa$ ).
Pascal's Principle: Pressure exerted on a fluid in a closed system is transferred equally to all parts. * $P_1 = P_2$ * $\frac{F_1}{A_1} = \frac{F_2}{A_2}$ * Output Force formula: $F_2 = \frac{F_1 \times A_2}{A_1}$

Mechanical Advantage in Hydraulics

$MA = \frac{\text{Output force}}{\text{Input force}}$

Example: If a jack lifts a $2000\,kg$ car ( $20000\,N$ ) using $100\,N$ input force, $MA = 200$ . Height is lost as force is gained; to lift the car $1\,mm$ , the input piston must move $200\,mm$ . To solve this, a reservoir and one-way values are used to allow multiple small strokes of a lever to lift the car incrementally.

Mechanical Control Systems

Ratchet and Pawl: A wheel with angled teeth (ratchet) and a lever (pawl) that allows movement in one direction only.
Cleats: Control movement of ropes. A Jam Cleat has horns to wedge the rope. A Cam Cleat uses spring-loaded teeth to grip.
Bicycle Brakes: Use calipers on a common pivot. Brake pads exert friction on the wheel rim when a cable is pulled.
Disc Brakes (Car): Hydraulic system where brake fluid travels from a master cylinder to a slave cylinder. The force is multiplied and used to press pistons and brake pads against a wheel disc to stop rotation.