Simple weather balloon? - RC Groups
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Feb 25, 2006, 06:07 PM
Studies the wind
ghoti's Avatar

Simple weather balloon?

I want to fill a small party balloon with hydrogen to release and study wind at altitude before I fly my AP plane. Can anyone tell me an easy, cheap simple and safe way to inflate just one balloon at a time? I beleive I can generate H2 through electrolysis of water but how do I get it into the balloon?
Thanks and Happy Landings! fish
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Feb 25, 2006, 09:16 PM
Registered User

Generating Hydrogen

Hi ghoti,

Cracking water is step 1. The problem with getting hydrogen into a baloon is the need to compress it. It would be easier for you to either buy a bottle of hydrogen gas from a gas supply house, or more practically use helium. I am sure you have heard this before, and I don't mean to burst your bubble. If you still want to try your experiment, go for it and learn. Just take precautions because hydrogen in the correct combination with air becomes explosive. Doesn't mean it will, just take precautions.

Feb 25, 2006, 09:36 PM
Studies the wind
ghoti's Avatar
Hi Rherman,
Thanks for the thoughts. All true. My inclination is I don't want the hassle of carrying and caring for a compressed gas bottle. I have 12 volts and water and a pinch of salt to make it conductive and a test tube to place over the H generating electrode. So it comes out at one atmosphere. How about passing it through some Tygon or surgical tube configured as a peristaltic pump with a circular shape and a couple or three rollers that get cranked around and around pinching the tube. All simple and manual it sounds like. Know where I can buy one?

Generate only enough H2 to meet the need, a balloon full-- and no more-- to store or worry about. The small quantity is less that what my chem professor used to demonstrate this in front of the class. This all comes across to me as totally safe. Any opinions? fish
Feb 26, 2006, 11:55 PM
Can you use a small fish tank air pump for this kind of thing?
Feb 27, 2006, 01:24 PM
Studies the wind
ghoti's Avatar

good idea

tomp999, thanks. That is worth looking into. I used to have one around here somewhere. If I can find it I will tear into it and see how it works. I could go from 12 volts to an inverter to run the motor. More later. fish
Mar 05, 2006, 09:04 AM
The Big Kahuna of Foam.
bkahuna's Avatar
Why not just fill a small trash bag? It will inflate with hardly any pressure.
Mar 20, 2006, 07:17 AM
Registered User

Simple weather balloon?

You guys are all looking for a complex way to make hydrogen. It is so easy if you come back to basics. I have filled dozens of party balloons by this method. Launched many into the sky with return notes; even got some replies.

You use Caustic Soda solution and Aluminum. The materials are readily obtainable, very cheap and no electricity or pressure pump is needed. It is all done chemically.

Buy a small tin of Caustic Soda (Sodium Hydroxide, NaOH) from your supermarket or hardware store. Cut up some strips of scrap aluminum sheet about 2 inches long and about 3/8 inch wide (narrow enough to fit into a wine bottle or quart beer bottle neck). Note: Don't use aircraft alclad sheet, it needs to be basic aluminum. Do this next step out in the yard or some open space.

Mix about two teaspoons of caustic soda crystals into about 6 ounces of water (It will get slightly warm as you do this) and pour this carefully into your large beer bottle or standard wine bottle. Put in enough so that you get about 2 inches depth of solution in the bottle.

Wipe the top of the bottle neck dry. Fold about 6 or eight of your aluminum strips into U shapes with a bit of a twist (this ensures they do not lay flat in the bottle; you want the maximum surface area exposed to the solution).

Poke your aluminum strips into the bottle. Slip your toy balloon over the top lip of the (dry) bottle neck. There is no need to tie it; the pressure required to inflate the balloon is insufficient to dislodge it.

As the Caustic Soda reacts with the Aluminum, Hydrogen is rapidly formed. It will take about 30 to 45 minutes to inflate a kids balloon about the size of a basketball or until you decide the balloons inflation limit. During this time the reaction will get progressively faster and pretty hot and produce quite a lot of froth inside the bottle, but so long as the froth and heat don't get too high, the hydrogen filling the balloon will stay dry and give very good lift.

If you get steam or froth in the balloon you are ruined, as the water vapor is too heavy and condenses on the inner surface.

When ready, pinch the balloon neck and remove it rapidly from the bottle. Stretch and tie a knot in the neck and for Christ's sake hold on to the balloon!

Tie on some string and anchor it well or keep it indoors within reach.

Move clear of the bottle, as the reduction in pressure may cause it to vent unpleasant froth and fumes. Don't ingest the vapor.

You experiment with various quantities of solution and aluminum strips to determine your optimum hydrogen yield before it gets too hot. You can only do one balloon per bottle for this reason.

NOTE: Caustic Soda is very harmful to eyes and skin, so do all this very carefully and keep it away from children. The hydrogen, in that sort of quantity is not much danger, but even so, keep balloons away from incendiary people (those idiots that smoke).

Write to me direct if you need any further details.

Don't increase any quantities without great care; the reaction gets very hot and will crack the bottle if to try to ramp up the power too much. You can't throttle it back once you are started! You will also bugger your balloons.

I haven't tried plastic bags. They might be easier, but the loss of back-pressure in the bottle might cause too much foaming.


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