TA 101: Technical Arts 2015-16 II Dr. Prishati Raychowdhury Department of Civil Engineering IIT Kanpur Office: FB 336; Phone: 6692 E-mail: prishati@iitk.ac.in

Lecture 7 Isometric Projection

Notice regarding AutoCAD Practice sessions are scheduled on Feb 5th, 6th, 12th, and 13th AutoCAD laboratory session (LA#7) is scheduled during Feb 22-25th (the week after mid sem) February 2016 Monday Tuesday Wednesday Thursday Friday Saturday Sunday 1 2 LECTURE 10 3.00-4.00 PM (L7) 3 4 LECTURE 11 2.00-3.00 PM (L7) 5 AutoCAD Practice (6-8 pm) 6 AutoCAD Practice (6-8 pm) 7 8 9 LECTURE 12 3.00-4.00 PM (L7) 10 11 LECTURE 13 2.00-3.00 PM (L7) 12 AutoCAD Practice (6-8 pm) 13 AutoCAD Practice (6-8 pm) 14 15 MID SEM 16 17 18 19 20 21 22 23 LECTURE 14 3.00-4.00 PM (L7) 24 25 LECTURE 15 2.00-3.00 PM (L7) 26 27 28 AutoCAD LAB: LA#7 (10 am-1 pm)

AutoCAD Schedule Practice session SL. No. Section Date Time Venue 1 B1 Feb 5, Friday 6-8 pm IME autoCAD lab 2 B2 3 B3 Northern Lab 4 B4 Feb 6, Saturday 5 B5 6 B6 7 B7 Feb 12, Friday 8 B8 9 B9 10 B10 Feb 13, Saturday 11 B11 12 B12

Notice regarding AutoCAD AutoCAD labs in NEW CORE LAB are open to all everyday from 8:00 am to 11:00 pm You are encouraged to go there and practice as per your convenience You will be given a handout for ready reference to the basic commands of autoCAD You are requested to go through the document and get familiar with the software We will spend a couple of lectures to learn about autoCAD

AutoCAD Schedule AutoCAD Laboratory Session (LA#7) SL. No. Section Day Date Time Venue 1 B1 Tue 23/02/2016 10 am – 1 pm IME autoCAD lab 2 B2 3 B3 Northern Lab 4 B4 Mon 22/02/2016 5 B5 6 B6 7 B7 Wed 24/02/2016 8 B8 9 B9 10 B10 Thu 25/02/2016 11 B11 12 B12

Review: Axonometric Projection 100 80 20 25 60 50 40 12 x y z x y z Orthographic Projection Axonometric Projection Multiple views required Shape and size unchanged Object not rotated, no foreshortening Better for manufacturing and detailing, not preferred for visualization Only one view is required; 3 faces are visible in one view Object rotated twice Shape distorted Size foreshortened Not good for manufacturing, but preferred for visualization

Review: Isometric Projection Equal foreshortening of three mutually perpendicular sides Foreshortening is about 82% Obtained by rotating the object 45o about vertical axis and forward tilting it by 35°16’

Isometric Projection vs. Isometric View 1 0.82 ? ? 0.82 Isometric Projection ? 0.82 Isometric Projection of A Cube A Isometric Drawing/View/Sketch Enlarge by 1.225 times 1.225 1.0 ? ? 1.0 Isometric Projection ? 1.0 Isometric Projection of B (Isometric Drawing/View of A) Cube B

Review: Isometric Scale Isometric Projections: Isometric lines drawn using isometric scale Foreshortened (82% of actual length) Isometric Drawing/View: Isometric lines drawn using 1:1 scale No foreshortening, take actual lengths

Isometric Projection Basics Isometric Lines Isometric planes 120 Isometric Box 30 Isometric Axes

Isometric Projection Basics In an isometric projection (or drawing), distances to be measured only along isometric lines parallel to any of the isometric axes Any line that does not run parallel to an isometric axis is called a non-isometric line Non-isometric lines include inclined and oblique lines that cannot be measured directly. They must be created by locating two end points on isometric planes

Constructing Isometric Views Isometric axes can be positioned in a number of ways to create different views of the same object Regular Isometric Axes at 30° to horizontal drawn upward from horizontal (Commonly used method) Reversed Isometric Axes at 30° to horizontal drawn downward from horizontal

Methods for Constructing Isometric Views Box Method: Box method is used when the non-isometric lines or their ends lie in isometric planes The object is assumed to be enclosed in a rectangular box The ends of the lines for the inclined edges are then located by measuring on or from the outlines of the box Coordinate or Offset Method: This method is adopted for objects in which neither non-isometric lines nor their ends lie in isometric planes Perpendiculars are dropped from each end of the edge to a horizontal or a vertical reference plane

Example: Box Envelope Method

Example: Without box

Another Example 20 40 30 45 10

Another Example 20 40 30 45 10

Isometric View

Procedure: Isometric Projection Choose the origin as the starting point (does not have to be a point on the object) Draw the isometric axes from the origin (@1200) Draw an isometric box corresponding to the maximum object dimensions All object edges parallel to the three principal axes are also parallel to the corresponding isometric axes. These object edges are called isometric lines All the object planes parallel to the three principal planes are called isometric planes Draw the isometric edges & planes first, locate ‘key points’ in isometric drawing, and then draw non-isometric object lines & planes using the ‘key points’ Hidden lines are generally not drawn

Isometric Projection Notes All isometric lines are foreshortened equally (82%) All non-isometric lines may or may not foreshorten and foreshortening ratio of such lines may vary disproportionately Projections of parallel lines will be parallel in isometric view All measurements can only be marked along isometric lines Measurement cannot be made on non-isometric lines Angles specified in degrees do not appear in their true size on isometric drawing Angles must be laid off with coordinates which are parallel to isometric axes

Difference with Orthographic Views Hidden Lines Omitted in isometric projections (or drawings) unless absolutely necessary to completely describe the object Most isometric projections (or drawings) do not have hidden lines

Circles and Center Lines Circles will become ellipse in isometric Draw ellipse using the four-centre method Center Lines Drawn only for showing symmetry or dimensioning Often not shown when communicating with non-technical people and not for engineering purposes

Dimension Lines Dimension lines, extension lines and lines being dimensioned lie in the same plane All dimensions and notes to be located outside the view whenever possible

Circles in Isometric View Orthographic View Isometric View

Non-Isometric Lines in Isometric View Inclined Line F E C E F D C H B D G I B G H A Isometric Line A I Orthographic View Isometric View

Angles in Isometric Views b 900 900 600 c 600 b 300 a 900 1200 1200 c 600

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