Design Refinement Page
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Table of Contents |
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| Author: Jon Evans | Team: Solar Car |
Design Refinement
From the several design solution concepts generated in the previous lab, it was necessary to refine the selection to two designs that could be modeled and explored further. This was done using a Quality Function Deployment (QFD) decision matrix. Two of these designs were then chosen for further development and were modeled using Pro/Engineer design software.
QFD Matrix
In this matrix, the design requirements were converted into engineering metrics. These metrics were given different weights based on their importance. The design alternatives were listed, and each design was compared with the others. Scores were given based on how well each design met the engineering metrics.
In this QFD decision matrix, the numerous design requirements were distilled into several engineering metrics. These were:
- Stiffness vs. weight
- This was given a weighting score of 1 because it was decided that stiffness was not a critical aspect of the design
- Durability
- This was also given a weight of 1 because the life cycle of the Solar Vehicle would only be a couple of years. Long term durability was not a critical consideration.
- Mass
- The mass of the design is important to the performance of the Solar Vehicle. Higher mass would lead to a lower top speed. For this reason, mass was given a weight of 3.
- Ease of Manufacture
- Because this project is working a tight time schedule, the design would need to be made quickly. Ease of manufacture relates directly to the amount of time needed to be spent on the fabrication of the design, so this metric was given a weight of 3.
- Air flow reliability
- This metric relates to how reliably the interface could be expected to supply air to the vehicle. This was one of the primary purposes of the design, and it was given a weighting factor of 3.
- Ease of repair/replacement
- If this component is damaged, it must be repaired or replaced. Constant repair of the ventilation system was not seen as a very likely occurrence, so the ease of repair was not a critical metric. It was given a weight of 1.
- Parts Cost
- At this stage of the design, the budget for the Solar Vehicle Design Team was extremely limited. Out of necessity, cost of the design became the primary consideration, and this metric was given a weight of 9.
The several designs compared in this matrix were variations on the three design concepts generated in the last stage of development. Many of these variations were material selection differences. The complete QFD matrix is shown below in Figure 1.
Figure 1: QFD Design Selection Matrix
As can be seen from the matrix, all three of the top scoring designs were of the same basic configuration but with differing materials. The top two designs (direct mounting and wheel well) were the concepts chosen to continue in the development process.
Solid Modeling
As mentioned above, the direct mounting and wheel well design concepts were chosen to model using solid modeling techniques. These solid models were developed using a combination of parts that would be machined and COTS parts. Many of the solid models for these COTS parts were obtained from McMaster Carr. Figures 2 and 3 show the wheel well design solid model. Figures 4 and 5 show the direct mounting solid model.
| Figure 2: Wheel Well Design | Figure 3: Wheel Well Cross-Section |
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| Figure 4: Direct Mounting Design | Figure 5: Direct Mounting Cross-Section |
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