Best Laid Plans...

There's one lesson I will never forget from working on Carnegie Mellon's Formula SAE Team: "figure out how much time you think a job will take. Then plan for three times that amount". It's surprisingly accurate, actually. I bring it up because I will be flying home on July 30 (in 122.2 hours, according to WolframAlpha) and I had rather hoped to be more or less done with everything. True, there's still an abstract due August 10 and a paper to write, but I could work on that anywhere. The plan was to take data today, do some analysis, get the abstract done, then fly home. I'd enjoy the last month of summer and work on the paper once school got started.

 
Hopefully that will remain largely true, but I certainly didn't get data collected today. Whilst I am a huge fan of learning by doing, it must be said that it usually results in designing one thing and building something completely different. Having finally got a new airfoil rapid-prototyped, I thought I would "only" have to force an aluminium tube through it and pin a steel rod into said tube. "Only". Ha.
 
Problem 1: due to the RP machine's resolution, the tube is .05 inches wider than the hole in the wing. Which means hammering the tube all the way through is a) very hard because of friction and b) not a good idea because it'll start to crack the wing in a very important place. Happily, I got around this by using two shorter tubes, one on each end. It occurred to me that only half of the tube is actually transferring load from the steel to the wing, while the other half was just there to hold the thing up. So there, problem averted.
 
Problem 2: I tried pinning the tube and the steel together over the weekend. They didn't want to play nicely, so I gave up and tried again this morning. There were playing slightly nicer and then the spring steel broke altogether. Oops. Now I could try making a new piece of spring steel, but Carnegie Mellon taught me another valuable lesson: when something breaks, it usually means that the design is no good, not that you were unlucky. In other words, if you build the same thing again, it will break the same way...again. Back to the improvisational-drawing board! I believe I've worked out a way to avoid the problem, but it involves a tool that is currently locked in the machine shop...which won't be open until Wednesday. Arg.
 
Like I said: figure out how much you need, then multiply it by three.
 
 
Posted in: Class of 2014