1. Technical Drawings

a) Drawing multiview

b) Drawing isometric

2. Motion Transmission Systems

Motion Transmission A) Definition: Relaying the same type of motion from one part of an object to another (rotational to rotational, translational to translational) Motion transmission systems contain: A driver component that initiates the motion At least a driven component that receive the motion and transfers it Some systems might also contain intermediate components between the driver and driven components

Motion Transmission 1. Gear trains Contains at least two gears that meet and mesh together Direction of components Alternates from one gear to another Reversibility Yes

Motion Transmission When building a gear train, you must consider: 1. The Gear teeth (they must be evenly spaced, the same size and have the same direction) 2. The Gear types (straight gears vs. bevel gears) 3. The Gear size (the higher the number of teeth, the slower the rotation) The larger the diameter the slower the rotation

Motion Transmission 2. Chain and sprocket Connects components that are far away from one another. The gears do not mesh together; they are connected with a chain (or sprocket) Direction of components The sprockets inside the sprocket will turn in the same direction. Reversibility Yes

Motion Transmission When building a chain and sprocket, you must consider that: The teeth on the sprocket are identical The chain links must mesh easily with the sprocket’s teeth The system requires constant lubrification The smaller the sprocket the fastest it turns

Motion Transmission 3. Worm and screw gear Consists of one endless screw and at least a gear It is not reversible When building a worm and screw gear, you must ensure that: The gear teeth match the worm’s grooves The driver must be the worm

Motion Transmission 4. Friction gear systems Similar to gear trains yet less efficient because the friction gears can slip. The larger the gear the slower the rotation

Motion Transmission 5. Belt and pulley system When building a belt and pulley system, you must ensure: Pulleys must contain a groove where the belt can fit The belt must adhere to the pulleys The smaller the pulley the faster it turns

3. Speed Change and Torque In Motion Transmission Systems

a) General Rule The speed varies with the number of teeth (or the diameter of the gears) If motion is transmitted to a smaller gear, the speed is increased If motion is transmitted to a larger gear, speed is decreased If motion is transmitted to a gear of equal size, there is no speed change

b) Scientific reason: Torque Definition: The two forces (of equal strength and of opposite direction), which cause a component to rotate around an axis

b) Scientific reason: Torque Types of Torque: Engine torque: increases the speed of components in mechanical systems Resisting torque: slows or stops the rotation of components in mechanical systems (e.g. friction)

b) Scientific reason: Torque The connection between Torque and speed change If the engine torque is = to the resisting torque, there is no speed change If the engine torque is greater than the resisting torque, there will be an increase in speed If the engine torque is smaller than the resisting torque, the object will slow down

Speed Change To find out the exact speed of the driven gear we must find the speed ratio: Speed ratio = diameter (or # of teeth) of the driver gear diameter (or # of teeth) of the driven gear What does this mean exactly? If I have a driver gear with 20 teeth and a driven gear with 10 teeth. The speed ratio is 2. This means that the driven gear is turning twice (2 x) as fast of the driver gear.

4. Motion Transformation systems

Motion Transformation A) Definition Relaying a motion from one part to another while altering the nature of the motion (e.g. rotation to translation or translation to rotation) B) Types of motion Transformation systems Rack and pinion Screw Gear systems Cam and follower Slider–Crank mechanism

Motion Transformation 1. Rack and Pinion Contains a rack (straight bar with teeth) and a pinion (gear) While building a rack and pinion you must ensure that: The teeth on the rack and on the pinion must be identical The system requires frequent lubrification The greater the number of teeth on the pinion the slower the rotation

Motion Transformation 2. Screw gear systems (2 Types) Contains a screw and a nut Type 1: the screw is the driver Transforms rotational motion into translational motion (e.g. jack to lift the car) Type 2: the nut is the driver Transforms translational motion into rotational motion

Motion Transformation 3) into Cam and Follower Rotational motion changed translation motion When building a cam and follower, you must ensure that: The follower must be guided in its translational motion The shape of the cam determines how the follower will move A device such as a return spring is usually necessary to keep the follower in continual contact with the cam.

Motion Transformation For a regular cam the axis of rotation is centered. For an eccentric cam the axis of rotation is off-centered.

Motion Transmission 4. Slider-crank mechanism This is the mechanisms used in pistons

Sometimes good, sometimes not 5. Adhesion and Friction Sometimes good, sometimes not

a) Adhesion Definition: Factors affecting adhesion: The tendency of two surfaces to remain in contact with each other (There tendency to cling to one another) Factors affecting adhesion: The nature of the material The presence of a lubricant Temperature Adhesion decreases with temperature State of the surface The smoother a surface, the less adhesion Perpendicular force Adhesion increases with the perpendicular force applied

b) Friction Definition: To reduce friction: Force that resists the slipping of one moving part over another To reduce friction: A) Polishing B) Lubrification Lubrification is the mechanical function of any part that reduces friction between two parts Liquid lubricants: oil, water Semi solid lubricants: Vaseline, vegetable fat Solid lubricant: Graphite, parrafin

6. Functional dimensioning

3. Functional Dimensioning Definition: Set of specific tolerances related to certain parts responsible for the smooth operation of an object. Tolerance: required manufacturing precision E.g. Distance between the gears E.g. Precision of the center of a gear E.g. Precision of the teeth

Tolerances Diameter 50 50 + 2 49 + 2 49 + 1 50 + 1

Tolerance 5 - 2 5 + 2 5 + 2

7. Mechanical Engineering Assembling parts

a) Typical functions to ensure proper functioning Sealing To seal Lubricating To reduce friction Guiding Allows specific motions Links To connect components together

b) Guides Freedom of motion Types of guides Rotation and/or translation around the x, y, or z axis Types of guides Rotational guide: ensures rotation Translation guide: ensures translation Helical guide: ensures rotation and translation around the same axis

c) Links There are always 4 characteristics/link Direct Indirect Flexible Rigid Removable Non-removable Partial Complete

Characteristic definitions Direct: The two pieces fit without requiring another component E.g. puzzle pieces E.g. Pen cap and the pen Indirect: The two pieces need an extra component to hold them together E.g. A poster and the wall E.g. 2 pieces of paper

Characteristic definitions Flexible: The linking component or materials are flexible E.g. Sticky tack E.g. velcro Rigid: The linking component or materials are non flexible E.g. A nail E.g. a dowel and a base

Characteristic definitions Removable: Can be removed without damaging the material or linking component E.g. Screw E.g. Sticky Tack Non-Removable: Cannot be removed without damaging the material or linking component E.g. A nail E.g. Glue

Characteristic definitions Complete: Does not allow any movement between the pieces Partial: Allows some movement between the pieces

Justify the use of each of these systems Why this system? Justify the use of each of these systems

Carjack Screw gear system

Car steering Rack and Pinion

Bottle Opener

Mechanical Engineering

Definition of mechanical properties Hardness Ability to resist indentation Elasticity: Ability to return to their original shape Resilience: Ability to resist shocks

Definition of mechanical properties Ductility: Ability to be stretched without breaking Malleability: Ability to be flattened or bent without breaking Stiffness: Ability to retain their shape when subjected to many constraints

Other properties Resistance to corrosion: Electrical conductivity: Ability to resist the effects of corrosive substances which cause the formation of rust, for example. Electrical conductivity: Ability to carry an electric current Thermal conductivity: Ability to transmit heat

What external forces are at play? Constraints What external forces are at play?

Constraints Constraints

Types of constraints Compression: Tension When a material is subjected to forces that tend to crush it Tension When a material is subjected to forces that tend to stretch it

Types of Constraints Torsion Shearing Deflection When a material is subjected to forces that tend to twist it Shearing When a material is subjected to forces that tend to cut it Deflection When a material is subject to forces that tend to bend it

Ways that materials react to the constraint Deformation Ways that materials react to the constraint

Types of material deformation Elastic: When the constraint leads to a temporary change in the shape or dimensions of the material. When the constraint is removed, the material returns to its original form.

Types of material deformation Plastic: The constraint leads to a permanent change in the shape or dimensions of the material. Even when the constraint is removed, the material remains deformed

Types of Material Deformation Fracture: The constraint is so intense that it breaks the material

Types of Materials

1. Wood Wood is a ligneous (fibrous) material whose bark has been removed. The mechanical properties differ depending on the type of wood Types of wood Hardwood (deciduous trees) More resistant to wear and harder than softwood Softwood (coniferous trees) Modified Wood (properties usually more constant)

Properties: Hardness, elasticity, resilience Low thermal and electric conductivity Easily shaped and assembled Light weight

Issues: Protection: It can rot, be subject to disease Properties depend on water content and conditions of growth Due to its organic nature, fungus, insects and micro-organisms can infest the wood. Protection: By varnishing, heating, painting or treating the wood, we can extend its lifetime.

2. Ceramics Ceramic is a solid non-metallic material obtained by heating inorganic matter containing various compounds Types of ceramic Crystalline Non-crystalline (glass)

Properties Issues Low thermal and electrical conductivity Hardness Resist corrosion Durable Issues Fragile to shocks and thermal shocks Wears easily in presence of acids and bases

3. Metals Metals: A material extracted from a mineral ore Metals are not usually used in their pure form, but are combined with other substances to improve their properties. This mixture is called an alloy (homogeneous mixture of two or more metals)

Properties (vary on the metal used) Usually shiny Good conductors (heat and electricity) Ductility and Malleability depend on the materials

Degradation Corrosion and Oxidation Protection: Coat the metal with a less corrosive metal (Zn, Au, Ag, Ni) Coat the metal with paint, enamel, grease, resin