Drawings

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Drawings

• Review

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Drawings

• Drawings are used to communicate information
• Sketch
• A drawing done without instruments or
  measurements, but conveys the general idea and
  proportions
• Technical Drawing
• Serves as a reference and presences all
  information is drawn with tools and is to scale

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Drawings

• Technical Drawings (cont)
• Geometric Layout
• Set of lines that form a technical drawing
• Basic Lines
• the standard graphic symbols that form a
  technical drawing (allow it to be a reference
  document)

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Drawings

• Technical Drawings (cont)
• Dimensioning
• The inclusion on a technical drawing of the
  dimension required to manufacture (create) an
  object
• Use dimension lines and extension lines
• Tolerance
• The imprecision allowed between a parts actual
  dimensions and the corresponding dimensions that
  appear on a technical drawing

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Drawings

• Scale
• The relationship between an objects dimensions
  in a drawing and the actual dimensions of the
  object
• Full-size scale or actual-size scale
• Reduction scale drawing is smaller than real
  life
• Enlargement scale drawing is bigger than real
  life

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Projections

• Projections
• a 3D representation of an object in 2D
• Types of Projections
• Orthogonal Projections
• Multiview (Orthographic) - Top, Front, Right
  view
• Isometric
• Oblique projections

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Projections

• Projections (cont)
• Exploded view
• Cross-section
• Drawing of an object as if it were cut by a
  cutting plane line

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Projections

• Projections (cont)
• Sections
• Partial representation of an object that presents
  only the objects surface on the cutting plane
• Types of section
• Revolved
• Removed

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Projections

• A) Definition
• A projection is a representation of a 3
  dimensional object in two dimensions
• Uses Basic Lines
• B) Types of projections
• 1. Orthogonal Projections
• Multiview
• Isometric
• 3. Oblique Projections

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Multiview Projection
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Isometric Projection
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Oblique Projection
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B) Types of Projections

• A) Multiview Projection
• Definition
• A 2 dimension representation of different views
  (faces) of an object (usually front, top and
  right side)
• Advantages
• Provides a complete description of the object
• Allows for the representation of all the
  measurements to scale or as is

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Multiview

• Top View
• Front view Right side view

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B) Types of Projections

• B) Isometric Projection
• Definition
• A drawing depicting all 3 dimensions of an object
• The axis (x, y, z) are at 120 degree angles of
  each other.

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Isometric

• The edge of your shape is facing the page
• You can see all three angles without distortions

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B) Types of Projections

• 2. Oblique Projections
• Definition
• A drawing depicting all 3 dimensions of an object
  where one side is parallel to the paper
• This distorts the depth of the object

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Please Note

• For construction purposes
• Use a combination of multiview and isometric
  projections as they show the overall design
• For a more detailed drawing showing all the
  parts, we have an exploded view

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Exploded view

• Purpose
• Projection accompanying the assembly instructions
  or specifications of an object
• Made up of different parts which are drawn
  separately from one another
• Exploded views include
• The names of each part (the nomenclature), the
  quantity and bill of materials (material list)

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1. Diagrams

• 3. Standards in diagrams
• Symbols for Force
• Compression
• Tension
• Shearing
• Symbols for movement
• Translational
• Rotational
• Helical

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1. Diagrams

• 3. Standards in diagrams
• Symbols for parts
• Screw/bolt
• Nut
• Symbols for guides
• Translational
• Rotational

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Motion Transmission Systems
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Motion Transmission

• A) Definition
• A motion transmission system transmits the same
  type of motion from one part of an object to
  another
• For example rotational to rotational

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Specific system vocabulary

• Motion transmission systems contain
• A driver a 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

Driven
Driver
Intermediate
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Specific system vocabulary

• Reversibility
• A system is considered reversible when the
  driven component could become the driver unit,
  and it would not change any of the motion types

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Motion Transmission

• B) Types of motion transmission systems
• Gear Train
• Chain and Sprocket
• Worm and Screw gear
• Friction Gears
• Belt and pulley

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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
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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
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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
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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
  sprockets teeth
• The system requires constant lubrification
• The smaller the sprocket the fastest it turns

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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 worms grooves
• The driver must be the worm

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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

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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

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Speed Change

• In Motion Transmission Systems

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Speed Change

• 1. Worm and screw gear
• For each turn of the worm, the gear moves by one
  tooth. The greater the number of teeth the
  slower the speed.

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Speed Change

• 2. Remaining systems
• 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

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Motion Transformation systems
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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
• SliderCrank mechanism

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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

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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

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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.

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Motion Transformation

• Eccentric vs. Regular cam
• In a regular cam, the axis of rotation is
  centered.
• In an eccentric cam the axis of rotation is
  off-centered.

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Motion Transmission

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