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JPL Annual Invention Challenge - ENTRY 10, 11, 12
 
 
What did we learn from the Bowling Ball Drop? This was a mechanical engineering problem and it was going to be tougher for us. The students always seem to be into aerodynamics, and this was a change. Beautiful problem though, because you have to do two opposite things at once. Both a soft landing and a fast time. The hardest engineering challenges require you to maximize two or more opposite things all at the same time. High mileage, safety, good performance, and low price in a car for example. All at the same time. It is fairly easy to get one, almost impossible to get all.

We toyed with the idea of ramming the ball in with an air pressure device, and fooled around with bicycle wheels and various containers for the ball, like trash cans and mixing bowls. This proved unwieldy as the weight of the ball was too much. Our kids asked the JPL engineer who won how he did it and how much it cost. He replied, "Oh, about $100. I just thought about the problem for a couple of days and drew up the plans and it worked."

They said "Mr. Nelson got all this stuff and we built all these designs over and over and this guy just built it right the first time." Well, that's what you do when you are learning!!!

Sometimes you get ideas just walking around and looking at materials. We found that 10 inch heating duct was perfect for moving a bowling ball this size. The important part was the interior diameter, just like the jelly bean launcher. It had to move the ball reliably but not have too close a tolerance. We spoke with Gary Gray when we arrived-what a great guy. He looked at our stuff and pronounced it good. The most fun at a contest like this is wrestling with a problem for months and seeing how everyone else has solved it. Sometimes other teams are using stuff you know won't work because you threw out that idea long ago.

Gary used EMT pipe just like we did. We started with copper because it was cheap and you could bend it, but it wasn't strong enough and it crimped instead of bending smoothly. We had to learn how to use a pipe bender. Our #1 entry always worked better than #2 because the curve was smoother. The ball rolled instead of banging around. The testing results were the same results as the contest. Gary's entry got stuck and we shared his pain. Tolerances that are too tight are no good either.

The designs that worked best were usually the simplest-Keep It Simple Stupid (KISS). Ours were simple and worked every time, but we could have spent more time thinking about how to get the ball in. The free fall devices got the best times and were tops, and the ones using materials like cloth and neoprene weren't. They slowed down the ball alright, but it would either get stuck or slow it down too much.

The germ of our idea was the old toy "Newton's Ladder"- 5 ball bearings on fishing line, so that when you pull out the first one it transfers the energy through the others to the last one, which bounces out. This appealed to us for two reasons: you could see where the energy was going and you could understand how the machine worked just by looking at it, and the energy absorption took place after the ball was over the pan. If you slow down the ball before you get to the pan the time will be too slow.

We had to learn to deal with the stress on the structure. On a bad day the bowling ball would come flying through the thing and blow out the back half of it. Tubing, plastic, and all would wind up in a big heap. Not good. We strengthened it with screws and glue and made sure the bottom wouldn't touch the pan by accident. Sometimes you learn that too stiff a structure isn't helpful either-you have to transfer the stress somewhere else. NASCAR learned this the hard way. Extremely stiff chassis transferred the energy into the driver and they had to develop ways to send it somewhere else. Same concept.

Our MESA crew did a fantastic job as usual and our kids were thrilled to be able to participate. Thanks to Paul and everyone at JPL for allowing us to learn and to laugh and to match wits with the best minds in Southern California.

Steve Nelson, Advisor

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For a photo gallery of the 2004 event, click here.
For the event rules please click here.


 
 
 
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