Technical drawing is a way to transmit or represent ideas, defining shapes, dimensions, colours. . .
Sketch
A sketch is a quick and basic representation of an idea we have in mind.
It is the simplest way to graphically represent an idea before having a physical model.
We use it for a first evaluation in a project.
It is hand drawn and has no details.
Drawing
The drawing must be clean, drawn with rulers, containing all necessary details (dimensions, scale, materials. ... ) and following a set of rules (standardization).
If the drawing is bigger or smaller than the real object, it should indicate the scale.
Standardization
Standardization is an agreement to always make something the same way.
For example, shoe sizes are standardized. You can buy a size 38, or a size 39, or a 40 ... but nobody can buy a 39.763
The disadvantage is that you can not have exactly your size.
The advantages are that you can reduce costs by mass producing and also so that stores can have a small stock.
Sometimes you will have ideas that you want to tell other people. Maybe you decide to design something. Then you draw the idea. You use standardized rules to make the drawing. Everybody knows the standardized rules so when someone else sees the drawing he will understand it
Isometric perspective
Isometric projection is a form of graphical projection, in which the three coordinate axes appear equally foreshortened and the angles between any two of them are 120 degrees.Cavalier Perspective
A point of the object is represented by three coordinates, x, y and z. On the drawing, it is represented by only two coordinates, "x" and " y". On the flat drawing, two axes, x and z on the figure, are perpendicular and the length on these axes are drawn with a 1:1 scale. The third axis, here "y", is drawn in diagonal, making an arbitrary angle with the others, usually 135°. The length of the third axis is not scaled.
Views (Floor, elevation and profile)
A section, is a view of a 3-dimensional object from the position of a plane through the object. A floor plan is a section viewed from the top. In such views, the portion of the object in front of the plane is omitted to reveal what lies beyond. In the case of a floor plan, the roof and upper portion of the walls may be omitted. Elevations or roof plans are orthographic projections, but they are not sections as their viewing plane is outside of the object.
Scaling means drawing the object bigger or smaller than it really is.
Scaling down (to draw smaller):
Scaling up (to draw bigger):We multiply all the dimensions by a number, and we use always the same number. We must indicate this number on the bottom left corner on the paper. For exemple "100:1" means we will multiply by one hundred.
ACTIVITIES
1. Draw a chess board in two dimensions, each of the 64 square board with two inches square.
2. Draw the following figures in isometric perspective, 1:1
3. Draw the following figures in cavalier perspective, 1:1, be careful with the reduction in the oblique axis.
4. Draw the views of the following figures.
