Axonometric Illustration Notes
Axonometric basically refers to any three axis drawing without vanishing points. These include isometric, di-metric, and trimetric. An oblique drawing is also axonometric, a di-metric if the receding axis is at 45 degrees, a trimetric if it is at 30 degrees.
Di-metric: Still with vertical axis, still the equal angles right and left.
Trimetric: Still with vertical axis, different angles right and left.
- Advantages of trimetric illustrations:
- More realistic in the sense that 99% of the time we see things in Trimetric.
- Isometric is rare and only one of a million possibilities.
- Allows us to emphasize relationships and details that we choose.
- Disadvantage: Require two or three scales to draw?
- Direct Construction from Grids or Scales.
Scales for the axes are common. Your instructor will hand out a typical set.
The scales are usually laid out as to Left, Right, and Vertical Axes Scales, and
Left, Right, and Horizontal Ellipse Exposures, in that order.
This is a simple cube drawing with 10 degree and 60 degree axes. This would be a 50-35-15 ellipse exposure trimetric illustration. The scales used result in a "projection" and not a "drawing". With a change of viewpoint to trimetric, we loose the luxury of 1 to 1 scales and the resulting isometric "drawing". Any dimension drawn in the "V" or vertical direction, for instance, would have to be multiplied by .84 before being placed in this illustration.
- How to Orient Ellipses on Axonometric Drawings
- Use a box method or
- Use the minor ellipse axes to orient the ellipse along the "thrust line" or center of the hole. In most cases, if the hole is drilled in the direction of one of the axis, the thrust line of the ellipse follows that same axis direction.
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