Sign Task

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marty3
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Re: Sign Task

Post by marty3 »

I feel like the balloon would reach it's terminal velocity rather quickly, thus it's momentum would be capped for a short enough string length such that ceiling height wouldn't matter. Is this not the case?
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Re: Sign Task

Post by chalker7 »

marty3 wrote:I feel like the balloon would reach it's terminal velocity rather quickly, thus it's momentum would be capped for a short enough string length such that ceiling height wouldn't matter. Is this not the case?
I too highly doubt they are using momentum to lift something. More likely, they are just using a really big balloon that they custom constructed (out of mylar or something) to maximize the lifting capacity. The absolute max a balloon the same size as a mission could lift is a bit over 200 grams (and that's discounting any tasks that obviously would take up some volume), so the winning Ohio team is well within that range.
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Re: Sign Task

Post by sj »

So i was wondering what exactly qualifies as a balloon? Would it be anything that is air tight, holds helium and only rises due to the buoyant force of the helium?
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Re: Sign Task

Post by illusionist »

That is my understanding of the requirements for meeting the "balloon" aspect of this event. Are you thinking about making a home-made balloon?
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Re: Sign Task

Post by sj »

Yup after seeing what Solon can do round balloons simply won't cut it. Also a side not the momentum idea does not work very well. Perhaps i works for lifting the mass an extra 5 inches but not 50 cm.
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Re: Sign Task

Post by Paradox21 »

Hmm, a custom mylar balloon the size of a Mission Possible would be quite heavy. My partner weighed a deflated standard 2 sheet 18 inch mylar balloon and told me it weighed about 50 grams. I wonder if it is possible to get more concentrated helium. I'm sure that the average helium tank is not pure helium, I wonder how much of the gas is actually helium and if it would be possible to somehow purify it further.
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Re: Sign Task

Post by sj »

We poked did some research and found that the tank we have is 95 -98 percent pure. Also are you sure a mylar balloon weighs that much. I don't think it does but i may be wrong...
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Re: Sign Task

Post by chalker7 »

Paradox21 wrote:Hmm, a custom mylar balloon the size of a Mission Possible would be quite heavy. My partner weighed a deflated standard 2 sheet 18 inch mylar balloon and told me it weighed about 50 grams. I wonder if it is possible to get more concentrated helium. I'm sure that the average helium tank is not pure helium, I wonder how much of the gas is actually helium and if it would be possible to somehow purify it further.
You can get nearly pure helium from welding supply companies, that's what I did when I was running balloon launch glider competitions. However, it comes in big tanks that might be tough to take to nationals. I bet a couple teams might have some and may share if you ask nicely. Otherwise, you might be able to find one in Madison if you are willing to get one there.

Also, I'm sure you could find thinner mylar online somewhere. The stuff we use on helicopters, wright stuff planes, etc is probably too thin to be useful but there must be something in between that and the thick stuff you measured.
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Re: Sign Task

Post by boomtech »

buzzbuzz wrote:My guess is they have an insanely large balloon; one that takes up half or more of the device, maybe custom made. Then, if the competition is in a gym or some place with a really high ceiling, they use the momentum of the balloon itself to pull up the weight. To do this, you just need a really long string between your balloon and the sign (weight). As the balloon rises, it will gain momentum. Once the string runs out, it yanks the sign over the top of the device. Keep in mind, there is not a requirement saying the sign must remain above the device. Another way to get more weight up is to minimize the height of the device, which in turn minimizes the distance the weight has to travel.
Even if the height of the device were minimized, wouldn't the top of the balloon be considered the top of the device? So the balloon would have to lift the sign past where its original top was... or am I wrong about that
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Re: Sign Task

Post by boomtech »

sj wrote:Yup after seeing what Solon can do round balloons simply won't cut it. Also a side not the momentum idea does not work very well. Perhaps i works for lifting the mass an extra 5 inches but not 50 cm.
We have done tests with the momentum idea, and it seems that there's an optimal length of string that varies depending on the size and shape of the balloon.

...also, 177 grams.....
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