The balsa wood bridge project was part of the civil engineering section and intended for us to design a bridge on paper to the exact dimensions in which we were supposed to build it. After given the amount of materials we would have to build the bridge and the guidelines/specifications for the bridge, we had to design the sides (the main part of the bridge including the substructure), the bottom, and the top to the exact dimensions on a piece of graph paper. After the design was complete, we had to cut/shape the pieces of the balsa wood using the design. Using metal pins and glue, we cut the pieces of wood, pinned them to the design and glued them together, repeating the process for sides of the bridge. Once the individual pieces were formed (two sides, top, and bottom), the individual pieces were glued together to form the bridge itself.
The design I settled for would, in theory, allow me to use very few pieces of wood while maintaining a solid and rock-steady structure, resulting in a lightweight and strong bridge. I chose to use a Pratt truss for the structure of the bridge and a Howe truss for the substructure, which I decided would create large areas of space in the individual triangles. The bottom and top of the bridge were simple pieces of balsa, which were laid across to connect the sides of the bridge, with only 3-4 inches between them.
The bridge was much more successful than I had originally predicted it to be, even for it being statically indeterminate. The design proved successful, as the bridge was incredibly lightweight and held 36 N. The section that proved to be the weakest in the bridge was the “road” of the bridge or, rather, the pieces, which were level to the table and connected the sides of the bridge together. To improve the design of my bridge, I would have to implement certain truss elements into the roadbed in order to support the weight of the sand.
The project taught me the importance of having a precise and carefully outlined design. The design was the key part of the project, as little to no adjustments could me made to the bridge after it was crafted. The project could be improved by having more realistic expectations for how much weight the bridges could support.
Potato Cannon Project:
The potato cannon project was part of the mechanical engineering section and intended for us to design a potato gun using the SketchUp program, gather a list of parts and materials, the costs for these parts and materials, and creating a presentation to present the best possible design specifications. As individual groups, we had to settle on a design for the potato gun. After a design was chosen, we gathered a list of parts we would need in order to construct the cannon. With these parts, we were able to use SketchUp to design every aspect of the cannon, including the dimensions. After the design was created and we researched prices in Home Depot, we had to create a presentation to present our design and cost analysis. The best designs with the most efficient and low-cost parts were chosen.
Our design included the implementation of a 4" x 24" PVC pipe (where combustion took place), a 2" x 48" PVC pipe (the smaller pipe connected to the combustion pipe), their respective adapters, a lantern lighter, and PVC primer. The cannon was designed to implement a longer barrel towards the end in order to maximize distance. The combustion pipe was designed to provide as much power as possible without sacrificing space. The equation we used predicted the design to be very effective, with the combustion pipe providing more than enough power and the long PVC pipe lending accuracy without sacrificing distance.
The results from the design, unfortunately, could only be predicted from the equation we used, as our design was not chosen. If we implemented certain features from other groups (as the final cannon had), our long barrel would have been shorter by at least 6 inches. The combustion chamber was still efficient, as were the other materials we had presented.
The potato gun project, similar to the balsa wood project, taught me the importance of researching and creating a solid and accurate outline/design before the actual construction of the cannon itself. I feel, however, that the project could have been more successful if we were given more time (maybe learn it in the beginning of the year) to fully learn how to use the SketchUp program. The program could have been implemented in a number of projects this year, so learning how to use it early on seems very beneficial to me.
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