Almost to the end of the semester. I’m done with classes. Finals are next week. I have two real test finals, one Tuesday (Physics) and one Wednesday (Calculus). I have take-home essay finals due Wednesday afternoon (Philosophy), and Thursday morning (History). Or, in place of the History essay, I can come to class and take a real essay final Thursday.

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Last week, I mentioned the Design competition. On to the results.

Our team did pretty well, the paddle wheel worked good, and we had about 30 points worth of whiffle balls. Then disaster struck. Well, it wasn’t that bad, but it was the end of the competition for us.

Our device used two motors, one for each of the rear wheels. This was the drive system, but it also was the steering. Bu going forward on the right wheel, adn backward on the left, the device would turn to the left. By manipulating the power to the two wheels, the device was very maneuverable. However, about 30 seconds before the end of the competition, the small set screw in the right motor fell out. (Left) The screw holds the spinning gear in the motor to the axle. After it was gone, the motor still turned, but the wheel didn’t turn with it.

That meant that the motion our device could make was a bog circle. We were close to out area, and Martin, the guy driving, almost got it arround the barrier infront setup area, where we were trying to get. If we’d had anohter 15 seconds or so, we might have gotten back. As it was, time ran out, and we, having returned 0 balls to the startup area, got 0 points.

Other teams did better, although some did worse. One team had their frame built entirely of balsa wood, and it was basically a jail cell without a bottom. That is, all the supports were vertical, with no cross bracing. They bumped into someone else, which kind of damaged their device, and then were accidentally rammed by another team–the picture is of their device after the competition. Surprisingly, after their device was destroyed, another device accidentally knocked a ball into their startup area, and they got a score of 2 points.

Another device was built to stand up, about 12 or so feet tall, and then fall down over the arena. It has two towers, and a cross bar between them at the top. After it fell, the cross-member would be pulled towards them, sweeping up all the balls that were inside the device. If it worked, it would have been a major point scorrer. However, as i said several times before the competition, it will either work perfectly, or not at all. There were so many things that could go wrong, all of them vital to the success of the deveice.

Did I mention that the device was probably 12 feet tall, when standing? And that the room where the practice board was set up had only about 10 foot ceilings? They never had tested a start from vertical. And did I mention that you only had two minutes to set up? THIS is what got them. When properly set up, the posts should be vertical, and parallel. This is so when it falls, they are the same distance apart the whole way back, rather like a train track. Imagine a train track where all of a sudden, it got narrower. The train would get stuck. They set it up with the bottoms of the posts too close together. I could instantly see that they would get stuck on the way back. However, their failure was more spectacular than that.

They had two lengths of 50# fishing line running to the top of the device, to stabilize it. Each length ran to one of the two posts. You may recall, the rules stated that once the time started, you could not touch teh device, and before the time started, the device had to be within the startup area (which had no upper limit). This meant that they had to use a remotely controlled mechanism to cut the strings. When they set up the device wrong, it caused the strings to not have as much tension on them as they should have. When they went to cut them, it took a bit longer than they epected, and then it cut one of the strings. I was talking with one of the team members afterwards, and he said “As soon as if cut only one string, I knew what was going to happen.”

The side that had had the sting cut started to fall, but was still supported on the other side. This caused the device to start twisting, and then the whole thing fell down, with the rails twisted, across each other. It had been a bit controversial if this group should be allowed to compete at the same time as other groups, and had been decided that as there was one extra goup, they would compete solo. So after their device collapsed, they decided to use the remainder of their time to give a demostration to the audience of how it would have worked. Unfortunately, the twisting had damaged the device, and it would no longer pull all the way in. Another score of 0.

If you want to see further results (just numbers, not pictures or commentary), see the course website. My team was E1, the team with the tower was E2, and the destroyed device was Team E7. All were in my section of the class, hence the E.

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I happened across a quiz, today:

Which File Extension are You?

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Got to run if I’m going to make it to lunch before it closes.

–Nathan