- Understanding Solid Objects
- Understanding Sketching Techniques
- 3.1 Technique of Lines
- 3.2 Sketching Straight Lines
- 3.3 Sketching Circles, Arcs, and Ellipses
- 3.4 Maintaining Proportions
- 3.5 One-View Drawings
- 3.6 Pictorial Sketching
- 3.7 Projection Methods
- 3.8 Axonometric Projection
- 3.9 Isometric Projection
- 3.10 Isometric Drawings
- 3.11 Making an Isometric Drawing
- 3.12 Offset Location Measurements
- 3.13 Hidden Lines and Centerlines
- 3.14 Angles in Isometric
- 3.15 Irregular Objects
- 3.16 Curves in Isometric
- 3.17 True Ellipses in Isometric
- 3.18 Orienting Ellipses in Isometric Drawings
- 3.19 Drawing Isometric Cylinders
- 3.20 Screw Threads in Isometric
- 3.21 Arcs in Isometric
- 3.22 spheres in Isometric
- 3.23 Oblique Sketches
- 3.24 Length of Receding Lines
- 3.25 Choice of Position in Oblique Drawings
- 3.26 Ellipses for Oblique Drawings
- 3.27 Angles in Oblique Projection
- 3.28 Sketching Assemblies
- 3.29 Sketching Perspectives
- 3.30 Curves and Circles in Perspective
- 3.31 Shading
- 3.32 Computer Graphics
- 3.33 Drawing on Drawing
- Key Words
- Chapter Summary
- Worksheets
- Review Questions
- Sketching Exercises
This chapter is from the book
This chapter is from the book
This chapter is from the book
3.3 Sketching Circles, Arcs, and Ellipses
Circles
Small circles can be sketched using one or two strokes, without blocking in any construction lines. Circle templates also make it easy to sketch circles of various sizes.
For better looking freehand sketched circles of larger sizes, try the construction methods shown here. Figure 3.26 shows an object with rounded features to sketch using circles, arcs, and ellipses.
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3.26 Many objects have rounded features that circles, arcs, and ellipses are used to represent. (Tim Ridley © Dorling Kindersley.)
TIP: The Freehand Compass
Using your hand like a compass, you can create circles and arcs with surprising accuracy after a few minutes of practice.
Place the tip of your little finger or the knuckle joint of your little finger at the center.
“Feed” the pencil out to the radius you want as you would do with a compass.
Hold this position rigidly and rotate the paper with your free hand.
STEP by STEP: METHODS FOR SKETCHING CIRCLES
Enclosing Square Method
Lightly sketch an enclosing square and mark the midpoint of each side.
Lightly draw in arcs to connect the midpoints.
Darken the final circle.
Centerline Method
Sketch the two centerlines of the circle.
Add light 45° radial lines and sketch light arcs across them at an estimated radius distance from the center.
Darken the final circle.
Paper Method
Mark the estimated radius on the edge of a card or scrap of paper and set off from the center as many points as desired.
Sketch the final circle through these points.
STEP by STEP
METHODS FOR SKETCHING ARCS
Radius Method
Locate the center of the arc and lightly block in perpendicular lines. Mark off the radius distance along the lines.
Draw a 45° line through the center point and mark off the radius distance along it.
Lightly sketch in the arc as shown. Darken the final arc.
Trammel Method
Locate the center of the arc and lightly block in perpendicular lines. Mark off the radius distance along the lines.
Mark the radius distance on a strip of paper and use it as a trammel.
Lightly sketch in the arc, then darken the final arc.
Tangent Method
Use these steps to draw arcs sketched to points of tangency.
Locate the center of the arc and sketch in the lines to which the arc is tangent.
Draw perpendiculars from the center to the tangent lines.
Draw in the arc tangent to the lines ending at the perpendicular lines.
Darken in the arc and then darken the lines from the points of tangency.
METHODS FOR SKETCHING ELLIPSES
Freehand Method
Rest your weight on your upper forearm and move the pencil rapidly above the paper in an elliptical path.
Lower the pencil to draw very light ellipses.
Darken the final ellipse.
Rectangle Method
Lightly sketch an enclosing rectangle.
Mark the midpoint of each side and sketch light tangent arcs.
Darken in the final ellipse.
Axes Method
Lightly sketch in the major and minor axes of the ellipse.
Mark the distance along the axes and lightly block in the ellipse.
Darken the final ellipse.
Trammel Method
To sketch accurate ellipses, you can make a trammel.
Mark half the desired length of the minor axis on the edge of a strip of paper (A-B). Using the same starting point, mark half the length of the major axis (A-C). (The measurements will overlap.)
Line up the last two trammel points (B and C) on the axes and mark a small dot at the location of the first point (A).
Move the trammel to different positions, keeping B and C on the axes, and mark more points at A. Sketch the final ellipse through the points.
Sketching Arcs
Sketching arcs is similar to sketching circles. In general, it is easier to hold your pencil on the inside of the curve. Look closely at the actual geometric constructions and carefully approximate points of tangency so that the arc touches a line or other entity at the right point.
Sketching Ellipses
If a circle is tipped away from your view, it appears as an ellipse. Figure 3.27 shows a coin viewed so that it appears as an ellipse. You can learn to sketch small ellipses with a free arm movement similar to the way you sketch circles, or you can use ellipse templates to help you easily sketch ellipses. These templates are usually grouped according to the amount a circular shape would be rotated to form the ellipse. They provide a number of sizes of ellipses on each template but usually include only one or two typical rotations.
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3.27 A Circle Seen as an Ellipse