1. 1. Technical Drawings

2. a) Drawing multiview

3. b) Drawing isometric

4. 2. Motion Transmission Systems

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 3. Speed Change and Torque
In Motion Transmission Systems

14. 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

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

16. 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)

17. 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

18. 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.

19. 4. Motion Transformation systems

20. 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

21. 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

22. 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

23. 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.

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

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

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

27. 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

28. 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

29. 6. Functional dimensioning

30. 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

31. Tolerances
Diameter 50
50 + 2
49 + 2
49 + 1
50 + 1

32. Tolerance
5 - 2
5 + 2
5 + 2

33. 7. Mechanical Engineering
Assembling parts

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

35. 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

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

37. 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

38. 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

39. 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

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

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

42. Carjack
Screw gear system

43. Car steering
Rack and Pinion

44. Bottle Opener

45. Mechanical Engineering

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

47. 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

48. 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

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

50. Constraints
Constraints

51. 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

52. 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

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

54. 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.

55. 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

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

57. Types of Materials

58. 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)

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

60. 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.

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

62. 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

63. 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)

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

65. 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