review of descriptive geometry

Lect 10 P. 1

Engineering H191 - Drafting / CAD

Autumn Quarter Gateway Engineering Education Coalition

Review of Descriptive Geometry

Lecture 10

Lect 10 P. 2



Topics For Today

• Quiz – CAEG – AutoCAD• Drawing Number 18 is due• Lab report due on Wednesday at the beginning

of the lab period• Lab Report – Follow the example, calc. % at each

speed, graph in %, use two mph groupings (24 and 25 – avg 24.5) or three mph groupings (24 thru 26 -- avg 25)

• Descriptive Geometry – Read BTG Chapter 11

Lect 10 P. 3



Review from Monday

• Lines and planes extend to infinity while we work with a small portion which we define.

• Lines and planes can be extended.

• Dihedral angle – The angle between two planes – smaller of the two. It can be found by finding the line of intersection and looking at the line of intersection as a point.

• Angle between a line and plane – This requires a view in which the plane is an edge and the line is true length.

Lect 10 P. 4



Review from Monday

• Downloaded a blank3d template – 4 viewports, 3D construction, world coordinates, cursor tracking – world

• Layout mode – Transferring the model to paper – tab at the bottom of screen

• The layout and the model or construction mode are all part of one file.

Lect 10 P. 5



Review from Monday

• VIEW – Using UCS menu– 3 UCS + plan (enter) (enter) – gives true size

of plane– Z UCS + plan (enter) (enter) – gives end view

of line which could provide edge view of a plane or a dihedral angle

Lect 10 P. 6



Construction Hint

• When you have created a line and then look down the line so the line appears as a point, it disappears in AutoCAD. When you know this is going to happen, place a point (+) at each end of the line.

• Save often but don’t overwrite the blank3D file.

Lect 10 P. 7



Key to Descriptive Geometry

Top

FrontRight Side

Know the location of the origin (0,0,0)

Lect 10 P. 8



Angle between a line and plane

• Required – a view where the line is true length and the plane is an edge

• In pencil construction, three auxiliary views are required 1) edge view of plane 2) true size of plane 3) edge view of plane and true length of line

• Using the UCS menu and the PLAN command shortens the process

Lect 10 P. 9



Today’s Assignment

• Dwg 19 – SGAC-4-1 – Angle between a line and a plane in space– Due at end of class today– Read Handout – steps for solving problems in

AutoCAD are provided

• Dwg 20 – SGAC-4-2 – Dihedral Angles– Due at beginning of next lecture– Read Handout – steps for solving problems in

AutoCAD are provide

review of descriptive geometry

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