Ch.4 Engineering Geometry & Construction

1. Ch.4 Engineering Geometry & Construction • Geometric construction and engineering geometry (4.1) • Coordinate spaces (4.3) • Geometric elements (4.4) • Points, lines, surfaces & solids (4.5) • Conic curves (4.6) We cannot cover all materials in this chapter in one lecture. Some of the definitions and concepts have been covered in your education up to this point (from elementary school). We place emphasis on quickly constructing necessary geometric elements. Terms you learn from this chapter have direct relevance to CAD.

2. Geometric construction and engineering geometry • Geometric construction  Act of constructing a geometry, especially using hand tools. • Engineering geometry  Basic geometric elements and forms used in engineering design. Dividing a line Cylinder

3. Engineering geometry classified • Manual drafting • AutoCAD

4. Coordinate space • 2-D Cartesian coordinate system

5. Coordinate space (cont.) • 3-D coordinate system

6. Coordinate space (cont.) • Right-hand rule for axes direction & positive direction of rotation on each axis  Note that counter clockwise is positive (default positive rotation of ACAD)

7. Coordinate space (cont.) • Polar coordinates, Cylindrical coordinates, & Spherical coordinates

8. Points, lines, circles, and arcs • In this lecture we focus on geometric construction techniques that are needed to do manual drafting assignments. • Dividing a line into equal parts (4.5.2)

9. Points, lines, circles, and arcs (cont.) • Constructing arcs tangent to two lines (4.5.3)

10. Points, lines, circles, and arcs (cont.) • Constructing an arc tangent to a line and another arc

11. Points, lines, circles, and arcs (cont.) • Constructing an arc tangent to two given arcs or circles

12. Points, lines, circles, and arcs (cont.) • Constructing an arc tangent to two given arcs

13. Points, lines, circles, and arcs (cont.) • Constructing an arc tangent to a given arc

14. Points, lines, circles, and arcs (cont.) • Constructing lines tangent to two circles o arcs, using a straightedge (a trial and error method)

15. Conic curves : parabolas Focus

16. Conic curves : Ellipses

17. Conic curves : Ellipses (cont.)

18. Conic curves : Ellipses (cont.)