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Engineering Drawings 29
A short series of lectures on Engineering Drawing as Part of ENGG1960
Introduction to Biomedical Engineering 1 By Paul BriozzoWhat is an Engineering Drawing ?
An Engineering Drawing is a technical (not artistic) drawing which
clearly defines and communicates a design to other interested parties.
Other parties may have an interest in design collaboration, procurement / purchasing,
costing, manufacturing, quality control, marketing, handling / packaging.Why do we need to know
about Engineering Drawings ?
• To allow our designs to develop from a thought or concept to a
design / sketch on “paper”.
• To enable us to communicate our designs / sketches to colleagues for
• To convert our sketches / designs into layout drawings which show
how our ideas link up to existing infrastructures.
• To include our design / sketches as part of a proposal for client /
management approval and review.
• To provide Manufacturers with working Engineering Drawings
based from our original designs / sketches. Consider the following description
of a “V‐Block”
MATERIAL: CAST IRONPictorial FreehandExamples of Layout Drawings
Collapsible Canoe Outrigger Design Project, 1998
Undergraduate Design Project under the Leadership of A/Prof. Harry Lipkin, Georgia Tech UniversityExamples of Layout Drawings
Lunar Module Landing Gear Plans, NASA, 1969Proposal Drawing
Engineering drawing by Harry C. Shoaf (Space Task Group Engineering
Division) of the proposed ʺlunar landerʺ to be used with an advanced
version of the Mercury spacecraft. (Shoaf, Drawing, Nov. 15, 1961.)
Lunar Lander, 1969
Surveyor 1 ,1966Engineering Drawing
Detail Drawing (Finish Drawing) of Connecting Rod, M.Jacek1973The History of Engineering Drawing
Free Hand Sketches –Leonardo DaVinci1500 AD
Design for a flying machine c1488
Anatomical study of the arm c1510
Sforza monumentGraphical Projections
st nd rd th
1 Angle 2 Angle 3 Angle 4 AnglePerspective
Staircase –two point perspective
Cube –two point perspective
Cube –one point perspective Cube –two point perspective Cube –two point perspectiveMethod and
Rules of Projections
• Select a view from the most advantageous position.
• Observe overall structure first.
• Note: parallelism, proportions and alignment.
Rules of Projection
• Object viewed from ∞.
• Parallel lines remain parallel.
• Proportions remain unchanged.
• Circles are always ellipses with the major axis of ellipse
perpendicular to the polar axis of circle.
• Transformation of 90°angles.Parallel Projection
st nd rd th
1 Angle 2 Angle 3 Angle 4 AngleOblique ProjectionOblique Projection
Cavalier and Cabinet Projections
• Cavalier views are not preferred. They show lines which represent
the depth of the object as being disproportionally long. Even though
they are parallel to each other, depth lines appear to diverge away
from each other.
• Cabinet views are preferred over Cavalier. The issue of depth
disproportionality and divergence is “somewhat” eliminated by
halving the depth dimension.Oblique Projection
4 Basic Rules
1. Place the object so that the view with the most detail is parallel to the picture plane.
2. Place the object so that the longest dimension runs horizontally across the sheet. Oblique Projection
4 Basic Rules
3. In some cases the previous rules conflict, and when this is so, Rule 1 has
preference as the advantage gained by having the irregular face without distortion is
greater than that gained by observing Rule 2.
4. Decisions about viewing an object in oblique projection should aim to show the
object so that its shape is most clearly presented and is conducive to showing its
• Projection lines are perpendicular to Projection Plane.
• Principal axes inclined to Projection Plane.
• Isometric (Equal Scaling)
•≠≠ TrimetricIsometric Dimetric