Project I
2003
For my junior MAE design class, our first (of two) major projects was to construct a crane. The minimum requirements were that it lift at least 130lbs 30inches out from the main beam and 48 inches off the ground. We were allowed to use up to 18cu in of 3/16in 7075-Al and 9cu in of 1/2in PVC. Other design factors which directly affected our grade was how much the crane weighed, what its volume was, and how fast it lifted the weight in addition to how much it lifted and how far up and out it lifted it. Needless to say, a design philosophy and concept direction was needed -- we chose to lift a little bit more than the minimum distances and to try to maximize the weight that our crane lifted.
We built a rough version of our crane, Conan the Barbarian, and tested it on 11/3/03. It failed at 715lbs but not due to any structural deficencies. As you can see in the picture, our crane gets narrower toward the top and, under large axial loading, the top parts of the side flanges began to move inward. Eventually, the flanges came in contact with the pulley and acted like a brake -- this stopped the pulled, but the 3hp motor just kept going. Not being made to experience such forces in that direction, our crane snapped.
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Realizing that we needed to reinforce the end of our crane, we took some material out of the base, added some at the
end of the webbing in the middle, and decided we were ready to test again! Conan the Destroyer (our second
crane) started out a little shaky at first. We realized that, due to some unintended geometrical alterations in the
design, our tension supports were now in compression rather than tension! We decided that we should take the time to
remedy this rather than having another crane fail so we moved the crane up a set of holes, got smaller pulleys, and
busted out some tension supports on the bansaw as fast as we could and the testing began anew. This time, we crushed
our previous lift and ultimately failed at 1235lbs!!! Believe it or not, we actually
built something that performed extremely well -- our 2.5lb crane lifted over 400times its own weight.
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Finally, after crazy days of building and testing and last minute changes, we were out.
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