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ENGR 114 Chapter 2: Scale and Projections

ENGR 114 Chapter 2: Scale and Projections Scale Scales are used to measure distances on technical drawings. Types of scales Mechanical Engineers Scale (Fractional divisions) Civil Engineer’s Scale (Division of 10) Metric Scale Architectural Scale (Fractional divisions)

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ENGR 114 Chapter 2: Scale and Projections

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  1. ENGR 114 Chapter 2: Scale and Projections

  2. Scale • Scales are used to measure distances on technical drawings. • Types of scales • Mechanical Engineers Scale (Fractional divisions) • Civil Engineer’s Scale (Division of 10) • Metric Scale • Architectural Scale (Fractional divisions) • Combination Scale

  3. Mechanical Engineer’s Scale • Mechanical Drawings are drawn in inches. • 16 Divisions per inch • Scales • 1:1 Full Size • 1:2 Half Size • 1:4 Quarter Size • 1:8 One Eight Size

  4. Civil Engineer’s Scale • Civil Drawings are drawn in feet as the base unit. • Scales commonly used • 1”:10’ 1”:100’ • 1”:20’ 1”:200’ • 1”:30’ 1”:300’ • 1”:40’ 1”:400’ • 1”:50’ 1”:500’ • 1”:60’ 1”:600’

  5. Metric Scale • Metric Mechanical Drawings are drawn in inches. • Metric Civil Drawings are drawn in meters. • Scale • 1:1 Full Size • 1:2 Half Size • 1:5 Fifth Size • 1:10 Tenth Size

  6. Drawing Scale • We use scale in drawing to represent objects in the appropriate size on our drawing sheet. • We can represent large objects on a B-Size sheet using scale. (1” = 50’) • We can represent small objects on B-Size Sheet using scale. (4:1) • What are some examples that you might want to represent in a drawing?

  7. Drawing Scales are Ratios • Drawing Size : Actual Size A rectangular box on a drawing with the scale of 2:1 has the measured dimensions 10” W x 16” L x 20” H. How large is the actual box?

  8. Drawing Scales are Ratios • Drawing Size : Actual Size You are looking at drawings for a proposed golf course. The distance from the tee-box to the hole is 12 inches. If the scale on the drawing is 1”:50’, how far is it from the tee-box to the hole.

  9. Understanding Projections • Behind every 2D drawing of an object is a space relationship involving the object and three “imagined” things: • The observer’s eye or station point • The plane of projection • The projectors • Also called visual rays or lines of sight

  10. Types of Projection • There are two main types of projection • Parallel projection – the projectors are parallel • Perspective projection – the projectors come together at the station point • Perspective drawings represent objects as we see them

  11. Types of Projection

  12. Types of Projection

  13. Perspective Projection • Perspective – The most realistic of the pictorial drawing styles because it is closest to the way that we see. • An ordinary photograph shows the view in perspective. • We will not cover this view in this class. • You can study it on you own. See Chapter 16 in you text. • A drawing class would be another option.

  14. Perspective Projection

  15. Types of Parallel Projection • Orthographic projections are a type of parallel projection • Orthographic (right angle) projections have parallel projectors that are perpendicular (90 degrees) to the plane of projection • In orthographic projection objects can be presented at true size or scaled at a proportion of their true size

  16. Types of Orthographic Projection • Multiview projection – A two dimensional representation of a three dimensional object. • It shows one or more necessary views of an object • Front, Rear, Top, Bottom, Right or Left

  17. Multi-view drawing

  18. Multiview DrawingsFirst- and Third-Angle Projection • There are two main systems used for projecting and unfolding the views: • Third-angle projection which is used in the United States, Canada and some other countries • First-angle projection which is primarily used in Europe and Asia • You should understand both methods

  19. Multiview DrawingsThird-angle Projection

  20. Multiview DrawingsFirst-angle Projection

  21. Types of Orthographic Projection • Axonometric projections • Isometric, Dimetric, and Trimetric

  22. Isometric Projection • For a cube an isometric view obtained by first looking straight towards one face. Next the cube is rotated ±45° about the vertical axis, followed by a rotation of approximately ±35.264° (precisely arcsin(tan 30°) ) about the horizontal axis

  23. Isometric Drawings

  24. Isometric Grid - 30˚

  25. Types of Parallel Projection • Oblique projection – when projectors are parallel to each other but are at an angle other than 90 degrees to the plane of projection • Oblique projections are commonly drawn at a 45˚ angle from the plane of projection.

  26. Oblique Projection

  27. Pictorial Projections Reviewed

  28. Types of Projection • Technical drawings of 3D objects usually use one of four standard types of projection • Multiview • Axonometric • Oblique • Perspective ORTHOGRAPHIC Parallel PICTORIAL

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