Minh Le Flag Pole Report

Flag Pole Report Minh Le ARCH 127 February 14, 2014

Brainstorming / Initial Modeling

My first response after reading the assignment is what shape I should execute to resist the most load. Circle seems to be a good choice because there is no edge in the circle, but chipboard would not be a good material to resist bending for a 20-inch circular pole. So is the triangular shape. To me, my first challenge is that a single–layer structure would not do very well, so I came upon the idea of interlocking 2 triangles together. Even if they are still single-layer structure, the interlocking joint would add some strength to the exterior structure. Also another interesting advantage about the interlock is that every edge is a small triangle, and when force is apply directly to the edges, it will be divided and transmitted sideward, just like how the triangle reacts. Playing with that shape-interlocking idea, I expand and explore into square shape, pentagon and hexagon. I realize that the more side I go up, the better the exterior layer resemble the circular shape, which is my first intend. Yet, as the exterior extends outward, the interior void inside the interlock also gets bigger, which would become the new problem to fill it out and / or support the exterior walls. So I decided to stay with a small number of sides. I started out with the square shape and interlocked into octagon. I like the fact that it has 4 sides. But since the diameter is so small (1 inch), the final structure is not as I expected at all. The interlocking joint is not strong enough due to the fact that the cut is too thin. And to deal with the interior void mean more structure , which leads to economical problem.


Final Model Since the square- octagon approach seems to result in many problems, I come back to the Triangle-Hexagon idea and stick with it. The interlock work great and support the exterior wall nicely. Since the edge is in triangular shape, the force applied directly from the outside would transmit to the side and be countered with the support from the inside. On of the main reasons, beside adding some strength to the structure, for I pick interlock technique is to connect several part together as one single unit (pole). I stay away from creating one, singe 20-inch pole is because chipboard is not strong or load resistant; I figure the shorter stick/pole would be stronger than the longer stick/pole. I make a total of six 5-inch triangular prisms and interlock them together. To resolve the interior void issue, in the cut of the interlocking ends/areas, instead of remove all the unnecessary small strip, I keep and push them all inside, add a few drops of glue to create an overlapping web. The inner void is not only filled up, since it is all from the exterior wall structure, it supports and strengthens the whole structure. The weak points in the pole structure are at the areas where there are no interlocking and connections. For the top half of the pole, I glue a long vertical strips on the side to strengthen as well as connect all the parts as one.


Supporting Structure Base structure: the reason I build up the base is to create a gap between top and bottom layers, giving the space to structurally supports the base-end of the pole. I extend the length of the pole all the way through the base structure, glue them together so they hold on together as one unit. Supporting structure: the flag pole itself is kind of “swingy” when I apply a force/push to it, so I attach the supporting strip on the side to strengthen the base of the pole. There are 3 levels of the supporting structure. What I hope for is that the triangular support (in plan view, it is the supports from the total of 6 opposite direction) will counter the pulling force; in the other words, from any direction there would be around 3 support forces. The supporting structure is loose, so it allows some sort of movement before it gets to the resisting point from the supporting strips, with hope that the load or the pulling force will somehow decrease by a little.


Test

Attempt 1: the first test resulted in separation from the supporting structure and the pole. The supporting structure actually failed its purpose, to be honest. The separation occurred because the glue connection is not strong to resist the pulling force. The pole structure does its job though. There is a slight bend, but it is not a major damage to the pole structure. Attempt 2: the second test (pulling from the opposite side from the first test) seemed to have a better result. The pole now is supported by the strip; the supporting structure and the flag pole still connect to each other. The big turn out of the test is the breaking point of the flag pole. It didn’t break at the third level supporting structure, but at the second level structure. The pole breaks at the weak point (where there is no interlocking ). Also, the tension from the second level supporting structure adds some tension into the breaking of the pole. It didn’t appear to me when I made the model, but the test might indeed find the weakest point of the pole (weak point with no reinforced vertical strips, tension from the supporting structure).


Next Step/ Response After the failure of the supporting structure, if I get another chance to modify the flag pole, I would aim for building a better/ stronger structure. My final model supporting structure mainly depends on the glue connection to the flag pole. The test proves that this approach is not the way to do it. On the next iteration, I would explore the strength of the chipboard strip itself. My intend would be to wrap the long strip of chipboard around the flag pole and then bury the strip under the base. By doing this way, the force applied would be distributed along the supporting strip and go under the base structure. I believe it would resist a lot more load/ force than my final design. I’m really happy with how the interlocking pole structure react to force. It breaks at its weakest point, which has no interlock or connection. If to improve, I’m thinking about running the interlocking and connection throughout the whole flag pole; or at least providing the vertical strip all the way to the base of the pole, hence adding more strength. In short, the pole structure react to force as I expected. The supporting structure needs more logical modification. I’m happy with the overall design of the model. END OF REPORT.

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Minh Le Flag Pole Report