Descriptive geometry for students in engineering science and architecture; a carefully graded course of instruction . ETRIC PROJECTION 71 This arrangement of three lines, A, B and C, provides a very useful means ofmaking single projections or plans which show three dimensions to defmite scales,and because of the three lines which serve as axes of direction for measurabledistances, the method is known as Axometric Projection. It will be recognized that the scale of measurement along each of thethree lines, A, B and C, or axes of projection, as they are called, in Fig. 70 at (ii),is the same, be
Descriptive geometry for students in engineering science and architecture; a carefully graded course of instruction . ETRIC PROJECTION 71 This arrangement of three lines, A, B and C, provides a very useful means ofmaking single projections or plans which show three dimensions to defmite scales,and because of the three lines which serve as axes of direction for measurabledistances, the method is known as Axometric Projection. It will be recognized that the scale of measurement along each of thethree lines, A, B and C, or axes of projection, as they are called, in Fig. 70 at (ii),is the same, because the axes are equally inclined to the projection plane. Thisis therefore referred to as Isometric—a special case of axometric projection. Thescales of measurement along the axes A, B and C in Figs. 71 and 72, however, areall different from one another, so that, for instance, 2 on the axis A is representedby a longer line than 2 on the axis B. As an illustration of the use of this method, let it be required to find the axo-metric projection of a skeleton cube, each face of which will appear as a foreshort-. FiG. 72. ened view of Fig. 73, (,i). There will be twelve bars of square section, each onerepresented by three lines, as suggested at (ii). There are three directions for theedges of a cube, four edges to each direction, therefore the three axes of projectionmay each contain an edge. Let two of the axes be at 25° and 45° respectively,to the projection plane. First find the axes .1, B and C and rabattements of them at .!_, B2 and €2-On these rabattements mark oft measurements taken from the edges of the squareat (i), and transfer them to the axes by perpendiculars to the trace lines. Thenby parallels the three upper faces of the cube, all foreshortened in appearance,may be found. Three of the bars are by this time represented, each by three the careful use of parallels each of the remaining nine bars may be found. Allthe twelve bars have square ends which m
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