ENGINEERING GRAPHICS 1E9 Lecture 1: Introduction Lecturer: Dr. Bidisha Ghosh (bghosh@tcd.ie)

Course Structure Graphics CAE Hand Drawing (part 1) -Dr. B. Ghosh Hand Drawing (part 2) -Dr. G. O’Donnell Graphics AutoCAD-Dr. S. Pavia CAE

Assessment Examination: 75% of the overall mark 3 sections (A, B and C) 2 questions per section 3 questions to be answered, one from each section Dr B. Ghosh : Sections A and B Dr G. O’Donnell : Section C Labs 25% - assessed by coursework 10 % AutoCAD 10% D.O. Tutorials Dr B. Gosh 5 % D.O. Assignment Dr G. O’Donnell

Time Table

Syllabus – Hand Drawing 1 Basic Construction Orthographic Projections Isometric Projections Auxiliary Views Perspective

Evaluation Examination (Sections A & B) Continuous Assessment (2/3 of the total examination marks) Continuous Assessment (10% of the total course marks) four drawing office tutorials

Aim of the Course Knowledge of engineering drawing instruments Understanding and interpretation of technical drawings Ability to develop projections of a 3D object

Reference Books Technical Draughtsmanship By Eanna O’Broin Engineering Drawing with Worked Examples By M.A. Parker & F. Pickup Technical Drawing By F. E. Giesecke, A. Mitchell, H. C. Spencer, I. L. Hill, J. T. Dygdon, J. E. Novak

Technical drawing is the language of engineers and designers Waterfall M. C. Escher

Topics of Interest Drawing Instruments Lines Dimensioning Basic construction

Drawing Board DRAWING INSTRUMENTS 1 Layout of a typical drawing shet should be same as the background of this presentation. Nameplate at the bottom right corner.

Drawing Sheets A Series Formats (mm) A0 841 × 1189 A1 594 × 841 A2 DRAWING INSTRUMENTS 2 Drawing Sheets A Series Formats (mm) A0 841 × 1189 A1 594 × 841 A2 420 × 594 A3 297 × 420 A4 210 × 297 A5 148 × 210 A6 105 × 148 A7 74 × 105

Layout of a Drawing Sheet DRAWING INSTRUMENTS 3 Layout of a Drawing Sheet Layout of a typical drawing sheet

Tee square/ Drafting Machine DRAWING INSTRUMENTS 4 Tee square/ Drafting Machine

DRAWING INSTRUMENTS 5 Set squares (a pair)

Irregular/ French curves DRAWING INSTRUMENTS 6 Irregular/ French curves

Compasses Divider Protractor Ruler/Scale Pencil, Eraser DRAWING INSTRUMENTS 7 Compasses Divider Protractor Ruler/Scale Pencil, Eraser

TYPES OF LINES 3 Main Types DRAWING LINES 1 HIDDEN LINES WHERE EXTENSION OF VISIBLE LINES SHOULD HAVE A GAP BETWEEN THE TWO Lines Single centre line for longitudinal view and crossed centre lines for cross sectional view

Lines to aid understanding DRAWING LINES 2 Lines to aid understanding

DIMENSIONING 1 Dimension Lines (DL) Position of DL

Alignment of DL DL of Small Features Dimensioning Angles Dimensioning Circles

DIMENSIONING 3

Correct Practice of Dimensioning Drawing should only carry dimensions needed to manufacture

Drawing Parallel Lines DRAWING LINES Drawing Parallel Lines

Drawing Perpendicular Lines DRAWING LINES Drawing Perpendicular Lines

DRAWING LINES Bisection of A Line Place your compass point on A and stretch the compass MORE THAN half way to point B. With this length, swing a large arc that will go BOTH above and below segment AB.  Without changing the span on the compass, place the compass point on B and swing the arc again.  The new arc should intersect the previous one above and below the segment AB. With your scale/ruler, connect the two points of intersection with a straight line. This new straight line bisects segment AB.  Label the point where the new line and AB cross as C. Segment AB has now been bisected and AC = CB.  A B

Divide A Line into Multiple Sections DRAWING LINES Divide A Line into Multiple Sections From one end of the given line AB (say, A) draw a line AC at a convenient angle Using a scale/ruler divide the BC into the required number of parts making them of any suitable length. Join the last point on line AC (say, C) to B Draw construction lines through the other points on the line AB which are parallel to CB

DRAWING LINES Bisection of An Angle Place the point of the compass on the vertex of angle BAC (point A). Stretch the compass to any length so long as it stays ON the angle. Swing an arc with the pencil that crosses both sides of angle ABC.  This will create two intersection points (E and F) with the sides of the angle. Place the compass point on E, stretch your compass to a sufficient length and draw another arc inside the angle - you do not need to cross the sides of the angle. Without changing the width of the compass, place the point of the compass on F and make a similar arc.  These two small arcs in the interior of the angle should be crossing each other. Connect the point of intersection of the two small arcs to the vertex A of the angle with a straight line.  

Find the Centre of an Arc DRAWING LINES Find the Centre of an Arc Select three points A, B and C on the arc and join AB and BC Bisect AB and BC. Fine the intersection point of the bisecting lines/bisectors. That is the centre of the arc.

Inscribe a Circle in a Triangle DRAWING LINES Inscribe a Circle in a Triangle Bisect angle ABC and angle BAC. Fine the intersection point of the bisecting lines/bisectors. That is the centre of the circle. The radius of the circle is the length of a perpendicular line on any of the sides of the triangle drawn from the centre of the circle.

Circumscribe a Circle on a Triangle DRAWING LINES Circumscribe a Circle on a Triangle Bisect sides AC and BC. Fine the intersection point of the bisecting lines/bisectors. That is the centre of the circle. The radius of the circle is the length of a line joining any one of the vertices of the triangle to the centre of the circle.

Notes for Tutorials The tutorials start next Monday in drawing office in museum building Each tutorial is worth 2.5% Bring your own drawing instruments Drawing sheets will be provided Students will not be allowed in the tutorial without instruments