So far we have looked at one view of an object. To accurately describe even the simplest object we need at least two Orthographic views. Typically an Elevation and a Plan are used. The Elevation typically gives us Heights and Widths, the Plan gives us Widths and Depths of the object. With these two views we can imagine the front and top of the object.
We view the object Orthographically, as we have done so far, only now we Project the Elevation onto a Plane behind the object, This Plane is called the Vertical Plane. The Elevation is projected like a shadow
The Plan is projected onto a Plane underneath the object, at 90 degrees to the Vertical Plane, this Plane is called the Horizontal Plane. The Plan is projected like a shadow.
Once the Plan and Elevation is Projected onto these Planes, the Planes unfold and the Plan is directly underneath the Elevation.
As you saw above the Plan goes underneath the Elevation. This is a fundamental principle of Orthographic projection.
Sometimes an End Elevation shows more detail than a Plan. From the End Elevation we get Heights and Depths of the object.
We follow the same steps as above only the End Elevation is projected onto a Plane beside the object, at 90 degrees to the Vertical Plane. This Plane is called a Profile Plane or an End Vertical Plane.
As you saw above, once the Planes unfold the End Elevation is directly beside the Elevation. This is a key principle of Orthographic Projection.
Also you may have noticed theEnd Elevation of the right hand side of the object goes to the left of the Elevation once the planes unfold. Once again this is a key principle of Orthographic Projection. Also note that theEnd Elevation of the left hand side of the object goes to the right of the Elevation.
While we have only dealt with two views, this is rarely enough to describe an object. We generally use three views. To do this we combine the two methods above. The method we have used is known as the Glass Box method. Below you can see the Glass Box method being used. In this scenario three sides of the Glass Box are being used. However we can use anything from 2 to 6 sides of the box.
The edges of the box where the Planes unfold are known as the XY line and the YY line. The XY line is the Horizontal edge that connects the Vertical and Horizontal Plane, and the Profile Plane and the Horizontal Plane.
The Horizontal edge that connects the Profile Plane and the Horizontal Plane is the YY line. The Vertical edge that connects the Vertical Plane and the Profile Plane is also the YY line. This is because when the Planes unfold, these edges line up and become one line.
Once the Planes have unfolded the XY and YY lines appear as shown. This is what you will draw on you sheet when you are doing Orthographic Problems in class.
How to draw an Orthographic Question
1. Once you have drawn the XY and YY lines you draw the Elevation.
2. You project the widths of the objects' features down past the XY line.
3. You draw in the Plan.
4. You project your Depths in Plan across to meet the YY line.
5. Using a 45 degree setsquare you project these points to meet the XY line
6. You project these points up Vertically
7. You Project your heights across from your Elevation to meet the lines from step 6.
8. You draw in your End Elevation.
Another way to get an End Elevation is using your compass. The only difference is in step 5.
5. You place the point of your compass where the YY and XY line cross and swing an arc to meet the XY line.
