Tutorial: Using Equations .................................................................................................
Figure 9.6 shows a 90-degree section of an auger blade. The outside diameter is 12 inches, and the
blade width is 3 inches. The overall height is 4 inches. In this case, the auger is represented as a
surface because the thickness is ignored. Surface features can be useful in situations like this (used
as construction geometry) and are discussed in Chapter 27.FIGURE 9.6A representation of the auger
On the CD-ROM
You can find the part for Figure 9.6 on the CD-ROM with the filename Chapter 9 Auger.sldprt. n
With this information, you can calculate the lengths of the 3D edges using a sketch and a simple
equation. In Figure 9.7, the hypotenuses of the triangles represent the helical edges of the inside
and outside of the auger. By making the triangles the same height as the auger section, and by
making the horizontal side of the triangle the same length as a quarter of the inside or outside
diameter by using simple equations, the geometry and sketch relations automatically calculate
the flat lengths of the inside and outside edges of the auger (length of triangle side = diameter of
circle × pi / 4). In this way, the triangle is used to simplify the calculation, and give it a visual
result.