Characteristic 1: Direct vs. Indirect Links Key question: do ...

Characteristic 1: Direct vs. Indirect Links Key question: do ...

Thermoplastic A thermoplastic is a plastic that, when heated, softens enough to be moulded; when cooled it hardens, retaining its new shape. Most of the plastics listed on the previous slide are thermoplastics. Alternatives to thermoplastics: Thermosetting plastics harden permanently when heated or exposed to an energy source Chemosetting plastics harden when two chemicals are mixed together (like epoxy) Recycling plastic Most of the thermoplastics listed on the last slide can be recycled, but

nylon and acrylic cant be. The plastics must be sorted before being recycled. Items made of plastic now have a sorting number stamped on them to make them easier to recycle Chapter 12.5 Guides and Links in Technical Objects Basic Mechanical Functions Technical objects are made of components Components are the parts and fluids that have a function in the object.

There are two very basic functions that component parts have: Guiding function: A guide helps control or guide the motion of a moving part in a technical object. Linking function: A link helps connect two parts of a technical object together. Types of motion Name of motion symbol example Unidirectional Translation (slide one way) Bidirectional Translation (slide both ways)

Unidirectional rotation (turn one way) Bidirectional rotation (turn both ways) Helical motion (unidirectional or bidirectional) (screw-like motion) A B Mechanical Guides Guides Two main types of guides are:

Rotational guides, which help a part to turn, twist or rotate In diagrams, the simplified symbol for a rotational guide is The motion symbol is or Translational guides, which help a part to slide or translate In diagrams, the simplified symbol for a translational guide is The motion symbol is or Mechanical Links

Links A link connects two or more parts of a technical object. Linking can be done by many things: Nails, spikes Screws Bolts, nuts, Rivets

Glue, Tape Etc. A link can also have a guide built into it, turning it into a sliding link or a rotating link. Link Characteristics Links have four pairs of characteristics. Every link has a characteristic from each pair. 1. 2. 3.

4. Direct link vs. Indirect link Rigid link vs. Flexible link Removable link vs. Permanent* link Complete link vs. Partial link *permanent is sometimes called non-removable When you read the section on links, make sure you list examples that illustrate the different link characteristics Characteristic 1: Direct vs. Indirect Links

Key question: do the two main pieces need anything to hold them together? Direct Links do not require anything else to hold them together. Example. A jar lid or a pen cap. Indirect Links need something else... (a nail, a screw, glue, a staple or tape) to hold them together:

Characteristic 2: Rigid vs. Flexible Links Key question: Is the link made from solid, rigid materials? Rigid links hold pieces together firmly, with no movement or flexibility. Head Rigid Link Handle Flexible links allow some flexibility or deformation between the pieces.

Lamp Tire Flexible Link Flexible Link Wheel hub battery Characteristic 3. Removable vs. Permanent Link Key question: Was the link designed to be taken apart easily? Removable links can be removed easily.

Screws, staples, snap together parts etc. Permanent links are very hard to remove. Taking them apart usually damages them. Glue, welds, mortar etc. Characteristic 4. Complete vs. Partial Key question: Can the parts move? In a complete link, there is no possible movement between

the parts. In a partial link there is possible movement between the parts. Link Types The six principal types of link are: 1. Fixed Link (always complete) 2. Rotating Link (AKA. Pivot link) 3. Sliding Link 4. Sliding & Rotating link (AKA Pivoting-sliding)

5. Spherical Link (AKA. Ball & Socket Link) 6. Helical Link: (AKA. Helicoidal Link) For each of the link types, give an example that illustrates how the link works. 1. Fixed Link There is no motion between the linked parts. Fixed links are always complete, never partial However they can be direct or indirect, rigid or flexible, permanent or removable No motion No motion No motion (when sealed)

2. Rotating Link The guided part can undergo rotation around one axis. (in other words, one part can rotate). Rotating links are always partial, never complete They can be direct or indirect, removable or permanent, rigid or flexible. Rotating links contain a rotational guide. 3. Sliding Link The guided part can undergo translational motion on one axis (in other words, one part can slide.) Sliding links are always partial, never complete. Sliding links contain a translational guide

4. Sliding Rotating Link The guided part can undergo rotational and translational motion on the same axis. (in other words, the part can rotate and slide at the same time.) 5. Spherical Link The guided part can undergo rotational motion in many directions. (in other words, it can rotate several ways) Spherical links are always partial, never complete. 6. Helical Link The guided part can undergo helical motion. (In other words, it twists and moves forward at the same time, like a screw.)

Total of 24 possible types of link (but not all of them are used) Type of Link (example) Direct vs. indirect Rigid vs. Flexible Permanent vs. Removable

Complete vs. partial Fixed Links Rigid (flexible) Permanent Removable Complete (glue, nail, weld)

Indirect Direct Never partial! Rotating Links Indirect Rigid Permanent Partial

(Rarely direct) (flexible) (Removable) Never Complete! Usually Indirect Rigid Permanent Or Removable

Partial Never Complete! Rigid (flexible) Permanent or Removable Never Complete! (doorknob, scissors) Sliding Link (sliding door, drawer)

Sliding/Rotating Link (latch) Spherical Link (Joysticks, ball joints) Helical Links (screws, faucets) (Rarely direct) Indirect (Rarely Direct)

Direct (flexible) Partial Rigid (flexible) Permanent (Rarely Indirect) (Removable)

Never Complete! Direct Rigid Removable Partial (Rarely Indirect) Common (Unusual) Impossible

(flexible) (permanent) Partial Never Complete! Helical Direct, Rigid, Removable, Partial Sample 2 Assignments on Links and Linking Functions.

Workbook page 207 to 210 Chapter 12.6 Complex Mechanical Functions Systems and Functions A system is a set of components that share the same function. A complex mechanical function is the role played by a set of components in transferring motion inside a technical object. There are two types of complex mechanical function: 1. Motion Transmission 2. Motion Transformation

Motion Transmission Motion transmission occurs when motion is relayed from one part to another without changing the nature of the motion In other words, if the first part rotates and the second part rotates it is transmission. If the first part slides (translates) and the second part slides it is still transmission But if the first part rotates and the second part slides, its not motion transmission (its transformation!) Examples of Motion Transmission Friction Gears

Gear 1 Gear 2 Simple Gears Belt and Pulley Chain & Sprocket Worm and Gear Pulley 1

Pulley 2 Notice All the transmission systems shown on the previous slide changed a rotation in one part into a rotation in another part. Rotation Rotation = Transmission Although none of the systems illustrated this, the following would also be true: Translation Translation = Transmission

Speed Change in Transmission One of the useful things about motion transmission is that it can change the speed of a rotation. In general, the larger wheels in transmission systems move slower, the smaller wheels move faster. Larger/more teeth on the driver or smaller/less teeth on driven component causes a speed increase. Motion Transformation Crank and Slider Rack and Pinion Cam and Follower Screw Gear The motion transformation systems shown changed the nature of the

motion from rotation to translation. Rotation Translation = Transformation Translation Rotation = Transformation Assignments on Complex Mechanical Functions Read pages 389 to 398 in your text book. Pages 211 to 218. Reminders: Test soon. See blackboard for the date and record it in your agenda. Also, all pages in the purple technology section of your workbook (up to page 218) will be due soon. Dates will be put on blackboard. Video Examples

Gears Pulleys Worm Gear Speed Reducer (with belt and pulley and chain & sprocket attachments) Rack & Pinion with Slider-crank A Camshaft (Cams and followers) Camshaft operating a valve (like a car engine) Electricity Electricity comes from the flow of electrons. Electrons are the negative particles in atoms. Electrons flow through conductors, such as the metal in wires. An electric current is the orderly flow of negatively charged electrons.

Two types of Electric Current Wire Direct Current (DC) is the kind that comes from a battery. The electrical systems in your car use Direct Current. In Direct Current all the electrons move in the same direction all the time. Wire

Alternating Current (AC) is the kind that comes from a generator. The electrical systems in your house use AC. In Alternating Current the electrons move back and forth many times per second (60 Hz in North America). Parts of an Electric Circuit Power Supply: The component that produces the electric current in a circuit. This can be a battery, a generator, a solar panel, or similar device. Conductors: Transmits the electrical current from one

part of the circuit to another. These are usually wires or metal strips. Insulation: Blocks an electrical current. The coating on wires, or the plastic caps on joined wires. Load: Transforms electrical energy into another type of energy Examples include light bulbs, heaters, motors, etc. Controls: The switches and devices that control the circuit. Push button switches, dimmer switches, rocker switches, magnetic switches, etc.

Protection: The components that automatically interrupt the flow of current in an emergency. Examples include fuses and circuit breakers Symbols of Electrical Components (for use in circuit diagrams) Power Supplies: Direct Current (battery) Alternating Current (generator) Conductor wires: Wires are drawn as straight lines, bends are simplified as right angles Loads:

Controls: Light bulb or lamp Resistor or heater Switch, Open (off) Switch, closed (on) Simple Circuit Diagram Switch (drawn in open or OFF position) Control

Power Supply (Battery) Light bulb Load for Energy transformation Wires Conductors Transmission or Transformation? Guide Crank

Slider Guide Hint: Answer: Transformation Unidirectional Rotation is transformed into bidirectional translation (turning into sliding) Transmission or Transformation? Pulley 1 Pulley 2

Hint: Answer: Transmission Unidirectional Rotation is transmitted to another wheel that does the same (turning to turning) The Manufacturing Process Measure (identify the size and/or position on the material) and Mark (trace lines or mark the reference points on material) the parts. Machine (forming parts into shape with equipment) the parts. (Saw, drill, shear, bend, forge, mould, etc.). Assemble (stamp, nail, glue, rivet, weld, etc.) and Finish (polish, stain, paint, varnish, etc.) the technical object.

Measuring Wood Before Cutting Calculate the length you need the piece of wood to be Measure that distance from the clean end of the wood. Measure twice, cut once. Mark the wood. Draw a line across the wood using a square. Put an X on the side of the wood you didnt measure... The scrap side Tips for cutting wood. 5. Cut on the scrap side Place the saw so that the edge of the blade is exactly on your line, and the width of the

blade is on the scrap side. 4. Put an X on the scrap side, Opposite the side you measured, so you dont accidentally cut the wrong side. X 3. Extend the mark across the wood Use a square to get the line straight. 2. Mark the measurement Use a pencil to make a small mark. S

A W 1. Measure twice, cut once Make sure that you have taken the measurement of your wood carefully! Using a Mitre Box to Cut Wood A mitre box can help you make a square cut on a piece of wood. The type of saw used with a mitre box is called a back saw.

Using A Mitre box Support the lip of the mitre box against the edge of the bench. Line up the piece of wood to be cut against the far side of the mitre box Cut away from yourself

Mitre Box Workbench

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