[islandlabs] I have an antenna for the balloon in my office...

John Teddy masterjediyoda at gmail.com
Thu Dec 17 17:57:24 EST 2009


Someone look at my figures and tell me if it makes any sense, or am I way
off.

2009/12/17 John Teddy <masterjediyoda at gmail.com>

> Since we already spent $65, it looks like our project total cost is going
> to be around ~$150 at least. So roughly the same as MIT. They got some stuff
> gratis which we did not. Maybe if we call some engineering / tech school in
> the Jersey area and ask one of the professors if they want to give us helium
> at no cost.
>
> 2009/12/17 John Teddy <masterjediyoda at gmail.com>
>
> So if I squish Bill and my email together, we need
>> *65.5 * 3.3 = 216.15*216 cubic feet of helium.
>>
>>
>> http://bit.ly/7Z4v6A .. I called this guy on ebay, that tank is 244 cubic
>> feet. He said it weighs 150 pounds full. ANd he said it could be rented for
>> $84.99. But he is in Florida. This gives us a rough idea of prices though.
>> he said to rent it and use all the helium in it, is $84.99 can it can be
>> returned after a few days or whatever.
>>
>> -John
>>
>> 2009/12/17 Burns, William <burns at cshl.edu>
>>
>>  Applying the given formula: (4/3*pi*R^3)
>>> Excel says: 65.5 cubic feet for a 5-ft diameter balloon.
>>>
>>> According to the Kaymont figures:
>>> http://www.kaymont.com/pages/sounding-balloons.cfm
>>>
>>> The launch diameter of a kaymont 350 (used by MIT) should have been 125
>>> cm if their payload was 250grams.
>>> The launch diameter of a kaymont 800 (used by I.L.) should be 150cm if
>>> our payload is 250grams.
>>>
>>> Scaling-up a 5-ft balloon by the same ratio gives us a 6-ft balloon...
>>> So (ballpark) our balloon should contain 113 cubic feet of helium.
>>>
>>> Who knows what size tank might contain that much helium?
>>>
>>> -Bill
>>>
>>>  ------------------------------
>>> *From:* list-bounces at islandlabs.org [mailto:list-bounces at islandlabs.org]
>>> *On Behalf Of *John Teddy
>>> *Sent:* Thursday, December 17, 2009 5:04 PM
>>> *To:* Island Labs main mailing list
>>> *Subject:* Re: [islandlabs] I have an antenna for the balloon in my
>>> office...
>>>
>>> I see, the person must have been mistaken. Or maybe they were talking
>>> about industrial tanks of larger size.
>>>
>>>
>>> http://www.target.com/gp/detail.html/185-8901296-2975720?ASIN=B000PGQ63O&AFID=Froogle&LNM=B000PGQ63O|Disposable_Helium_Tank&ci_src=14110944&ci_sku=B000PGQ63O&ref=tgt_adv_XSG10001<http://www.target.com/gp/detail.html/185-8901296-2975720?ASIN=B000PGQ63O&AFID=Froogle&LNM=B000PGQ63O%7CDisposable_Helium_Tank&ci_src=14110944&ci_sku=B000PGQ63O&ref=tgt_adv_XSG10001>
>>>
>>> This is a 12lb tank, and holds 15 cubic feet of helium. It only costs
>>> $50.
>>>
>>> I don't think 15 cubic feet of helium be nearly enough.
>>>
>>> The MIT balloon was 5 feet diameter at launch, and 20 feet at burst. So
>>> ours will be under 10 feet diamater at launch, and under 40 feet diamater at
>>> burst. My figures are off, need the sphere formula. 4/3*π*radius3
>>>
>>> I don't know what the weight in the balloon (we have 800gram balloon,
>>> they used 350 gram right?), translates to as far as diameter and cubic feet
>>> of helium.
>>>
>>> From the guide:          "each cubic foot of helium can lift 28g" and
>>> "each pound of free lift would me 300feet per minute of ascension"
>>>
>>>
>>>
>>> http://www.balloonsandhelium.net/heliumtanksforsale.html <--- they are
>>> way to expensive to buy. Rent or launch at a party store are the only
>>> options. And the weight should definitely be under 100 pounds as you said
>>> Mark.
>>>
>>>
>>> They don't actually say in the guide how much helium they use I believe.
>>> Does anyone see a figure on how much helium the MIT guys used? They use an
>>> example of "61 cubic feet of helium" to describe an example for a formula,
>>> but that doesn't mean that is how much they used. If we need 61 cubic feet
>>> of helium this target tank is not nearly big enough.
>>>
>>>
>>>
>>>
>>>
>>> As far as the antenna goes, it was bought with a cellphone modem, it's
>>> designed to be used for cell phones. It's omni-directional, long, and
>>> quality. And it has the wire connector we need which attaches to the phone
>>> already I believe, so no soldering.
>>>
>>>
>>>
>>> On Thu, Dec 17, 2009 at 3:30 PM, Mark Drago <markdrago at gmail.com> wrote:
>>>
>>>> Unless the large helium tank is obscenely large, it's not 500 pounds.
>>>> I worked at a party store that rented tanks in 3 sizes (small, medium,
>>>> large) and had a fourth size for our own uses (jumbo).  The jumbo
>>>> tanks were easy for one person to roll around on their edge, but were
>>>> too heavy to really pick up and carry.  I would say they were easily
>>>> under 100 pounds, probably closer to 60 or 70.  This is a rough guess
>>>> as it has been 10 years since I moved one.  But I can definitely say
>>>> they were not 500 pounds.
>>>>
>>>> Mark.
>>>>
>>>> On Thu, Dec 17, 2009 at 15:13, John Teddy <masterjediyoda at gmail.com>
>>>> wrote:
>>>> > http://i45.tinypic.com/riaop5.jpg and
>>>> http://i50.tinypic.com/1htb15.jpg
>>>> >
>>>> > This antenna is already rigged to connect to a usb cellular modem,
>>>> that is
>>>> > able the size of a large thumb drive. So I believe this connector
>>>> should
>>>> > work with a lot of cell phones also. When the phone comes we ordered,
>>>> I will
>>>> > bring this antenna and see if it fits.
>>>> >
>>>> > I believe the remaining parts we need are: parachute and helium (and
>>>> some
>>>> > string/rope to connect it all, and other little things which are easy
>>>> to
>>>> > get).
>>>> >
>>>> >
>>>> > We need to calculate how much helium we will need for the baloon. As
>>>> it was
>>>> > explained to me yesterday, the large helium tank can weigh up to 500
>>>> pounds.
>>>> > So this is exceedingly difficult to carry around. If anyone can crunch
>>>> the
>>>> > numbers and figure out how much helium we would need, and how much
>>>> each size
>>>> > tank can hold.. that would be helpful.
>>>> >
>>>> > -John
>>>> >
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>>>> >
>>>> >
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>>>
>>>
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