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Continued from page 1
The following example details the creation of a simple hood concept (Fig. 1) that might be used on a BAJA racing vehicle.
Figure 1.
Step 1. Sketch the body curves. The hood is sketched in half in three views, basically to show the shape of the edges of the metal. The final hood is essentially made up of a top surface, a side surface, and a front surface. This is like orthographic drafting in a 3D space. Not all of the lines connect and it looks as if there are gaps. By the time the body curves are completed, though, it looks a lot like a 3D wire frame model.
- The top view is sketched first to get the general shape of the hood to fit the vehicle frame. The outermost curves are for the perimeter of the hood (Figs. 2a-b).
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Figure 2a (click to enlarge)
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Figure 2b (click to enlarge)
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- In the top view, the crest curve is constructed. This curve defines the edges where three surfaces intersect. Reference the necessary points from the previous curve in order to maintain relationships (Figs. 3a-b).
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Figure 3a (click to enlarge)
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Figure 3b (click to enlarge)
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- The side view (or profile) is sketched next, showing the top line of the hood at the centerline (Figs. 4a-b). Note: The key is to reference the start and end points of each curve entity from the top body curve set into this sketch. Then use those references to build the profile sketch.
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Figure 4a (click to enlarge)
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Figure 4b (click to enlarge)
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- The front view is sketched next to show the rear edge of the metal. Again, all of the curves are tied to the previous set of sketches (Figs. 5a-b).
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Figure 5a (click to enlarge)
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Figure 5b (click to enlarge)
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- In the side view, the crest curve is constructed, which is the intersection of the top and side surfaces (Figs 6a-b). This is the same curve mentioned earlier that would be hard to dimension under normal model creation practices. In this case, it is fully defined by the curves. Note: The key is to reference the start and end points of each curve entity from the previous curves.
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Figure 6a (click to enlarge)
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Figure 6b (click to enlarge)
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- In the front view, the crest curve is constructed, which is the intersection of the top and front surfaces (Figs. 7a-b). The previous two curves are used as references for this curve.
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Figure 7a (click to enlarge)
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Figure 7b (click to enlarge)
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Before continuing, modify some of the dimensions that control the shape to determine whether the model will regenerate. This is the best time to test the robustness of the model. If the model fails, then go back and make the necessary modifications to the sketches and review the relationship constraints.
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