Descriptive Geometry was a graphical technique used for analysis of lines and planes in three dimensions. Its principles enabled an engineer to obtain true lengths, true shapes, true angles, distances, and intersection shapes from any two orthogonal views, and then recreate them in any view. Descriptive Geometry was a closely guarded military secret for many years. Its disclosure was an offense punishable by death. With its expertise, France remained the prime military power in Europe until the early 20th century, when improved ordnance, mobile mechanized armies, and airpower once again made fortifications obsolete.
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The classical pentagon shape of the old fortresses is still familiar today.
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part1
As projects become more complex, many people need to become involved besides the originating engineer. To convey the design to others, graphics are invaluable for understanding three dimensional designs. In engineering, a picture is truly worth a thousand words.
click here to continueefacture, this product requires the combined efforts of many engineers from different disciplines. Engineering graphics help each engineer understand exact specifications of every part that goes into the product.
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Chapter 1: Introduction
The objectives of this chapter are to:
Provide a short history on the development of engineering design graphics.
Outline the present usefulness of engineering design graphics.
Motivate students to study and learn engineering design graphics.
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Begin Lesson
useful
You have reached the end of the Introduction. To review the material, go to the next page. To continue to Sketching, click the button below. below.
Prior to the 18th century, most engineering was for military purposes. However, new discoveries and applications precipitated new areas of study within the broader field of engineering.
txt1750
While military engineering produced ships, guns, and forts, civil engineering built roads and bridges for public use.
txt1850
With the advent of the steam engine, mechanical engineering was born. Other applications of this new discipline included boilers and machine tools.
txt1875
Electrical engineering emerged from studies of motors, generators, and the design and control of power distribution systems.
txt1895
The Industrial Revolution, specifically the oil industry, brought about a shift in use of whale blubber to fossil oil and fuel. Chemical engineering arose to fulfill the demand, supplying new refining processes.
txt1950
Efforts made to find new methods of power production resulted in the development of nuclear engineering. Industrial engineering increased productivity through studies of efficiency and material flow..
The timeline to the left displays the past 300 years and the development, in that time, of the different engineering disciplines.
Click either the date or the discipline to learn more about it.
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This animation demonstrates the assembly of a computer disk drive. From concept to development to manufacture, this product requires the combined efforts of many engineers from different disciplines. Engineering graphics help each engineer understand the exact specifications of every part that goes into the product.
One of the problems with the ancient fort designs was that once the opposing army was able to reach the base of the walls, it became difficult to defend the fort. During the medeival era, towers were incorporated into the designs. This modification allowed the opposing army to be attacked by crossfire, even at the base of the walls. The engineering analysis became slightly more complicated, but still do-able with relatively simple techniques.
Problems!
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The medieval fortifications worked very well against armies that were armed with swords, spears, arrows, and even catapults. However, toward the end of the medieval era, gunpowder and cannon were invented. These inventions made almost all fortifications at that time obsolete. Consequently, a new concept in fortification was needed, and developed. Using filled angled walls, which would still be too steep to scale easily, it was discovered that fortresses would not crumble under cannon shot. Angled walls can still be seen in many modern military designs..
Gun Powder
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After the medieval era, the square-walled perimeter of fortresses evolved into a more complicated polygon shape. With this design, any single wall was defensible from at least three other walls. Together with angled walls, the fortress would be defensible even against an army armed with cannon. A good example of this type of fortress was Fort Pitt, which was built during the early 1700's at the intersection of the Allegheny, Ohio, and Monongahela rivers in Pennsylvania. The fortress was able to control river traffic, and therefor also the trade, over a large section of the territory. The city of Pittsburgh grew up around the fort.
Polygonal Shape
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The post-medieval fortress designs were geometrically complicated. Calculations of material volume, surface area, lengths of timbers, and shapes of intersections were no longer simple. However, the French became very good at this type of analysis. In fact, Fort Pitt was a French design. The person most responsible for the French expertise was Gaspard Monge, who developed the principle of Descriptive Geometry...
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:HDMEDIAPATH
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:CDMEDIAPATH
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Introduction
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During the ancient and medieval eras, one of the most important engineering functions was the design of fortifications. Fortifications functioned to protect valuables from opposing armies. Ancient designs were simply a series of high vertical walls. The problems that needed to be solved were also simple. The designers needed to determine the amounts of dirt, stone, brick, and mortar that would be needed; the amount and sizes of timber; and the methods for getting the needed materials.
Ancient Design
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chris
&File
E&xit Alt+F4
Exit the program
&Navigate
navigate
&First Page Ctrl+Home
first
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&Go to Page... Ctrl+G
Introduction
intro
Go to Introduction chapter
Objectives
intro1
History
intro2
Usefulness
intro3
Sketching
sketch
Go to Sketching chapter
Objectives
Techniques
Objects
Cartooning
Engineering Drawings
formDraw
Go to Formal Drawings chapter
Objectives
Format
Working Drawings
Othogonal Projection
ortho
Go to Orthogonal Projection chapter
Objectives
orth1
Theory
orth2
Standard Views
orth3
Auxiliary Views
orth4
Common Practices
orth5
orth6
Pictorials
pictorials
Go to Pictorials chapter
Objectives
pict1
Oblique View
pict2
Isometric View
pict3
Perspective View
pict4
pict5
Sections
sections
Go to Sections chpater
Objectives
Full Section
Half Section
Offset Section
Broken-Out Section
Revolved Section
Removed Section
Common Practices
Dimensioning
dimension
Go to Dimensioning chapter
Objectives
Definitions
Guidelines
Common Shorthand
Tolerancing
tolerance
Go to Tolerancing chapter
Objectives
Definitions
Practical Fabrication Tolerances
True Position
Datums
Surface Features
Descriptive Geometry
descGeom
Go to Descriptive Geometry chapter
Objectives
Basic Principles and Relationships
Line Visibility
Distance Between Lines
Edge Views and True Shapes
Dihedral Angles
Intersection of a Line and a Plane
Intersection of Two Planes
Intersection of a Plane and a Solid
Intersection of Solids
Surface Developments
Contours and Cut-and-Fill
Shadows
&Main Menu Ctrl+Alt+Home
Go to the main menu
&Options
options
&Audio
Mute Ctrl+M
OnOff
Turns audio on or off
Volume...
setVolume
Set the volume of audio
&Page Controls
controls
Displays/Hides the Navigation Control Bar
&Help
Instructions F1
tutor
How to use the program
About the Authors
authors
Information about the authors
Prof. Dennis K. Lieu
Chris Casey
Su Shien Pang
Paul Krueger
Allison Okamura
Acknowledgments
others
Copyright Info
copyright
tutor
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history1
Engineering - The profession in which knowledge of mathematical and natural sciences, gained by study, experience, and practice, is applied with judgement to develop and utilize economically the materials and forces of nature for the benefit of mankind..........................
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The Egyptian pyramids, which served as tombs for the pharoahs, were the world's first significant engineering structures. However, since no documentation of their means of construction exists today, no one can recreate them or learn from their builders' mistakes.....
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In the first century BC, the compressive strength of stone was utilized in the Roman Arch to minimize material use while retaining the strength of a solid structure. Both the Roman Arch and the Roman Road, which networked the empire, were documented by Marcus Vitruvius. Because he recorded both their design and means of construction, such designs are still used today......
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The medieval era brought the flying buttress, a variation of the Roman Arch. The flying buttress permitted the construction of large enclosed areas, such as cathedrals..