Hydrogen Generator

[Tim]

This is very cool. My son is interested in blimps and has asked me why he can't get hydrogen gas to experiment with. I'd love to build the 120V version. . . you WILL post complete instructions, pretty please??

Two thoughts:

(1) Farm it out to the MakerGear community. I'd be willing to print a few and mail them back to you. See how the "distributed server farm" idea works for 3D printers.

(2) If enough people build these things, you won't have to rant about the lack of hydrogen gas availability any more.

[kyeakel]

Long ago, 1965 or so, I was in Cub Scouts. My father and I made a hot air balloon model and filled it with hydrogen. On it's maiden flight it got somewhat near a light bulb and blew up with enough force to push both of us back into the wall. The balloon was a standard round kids birthday party balloon. Making dangerous things with my Dad brings back memories...

Kipp

[PcS]

I volunteer to print a few as well !!! Seems like a neat idea and cool project !!! I have always wanted a giant balloon that was large enough to make me ...almost weightless. The idea of being able.to jump and float weightless for even a short time would be amazing !!!

[pyronaught]

Long ago, 1965 or so, I was in Cub Scouts. My father and I made a hot air balloon model and filled it with hydrogen. On it's maiden flight it got somewhat near a light bulb and blew up with enough force to push both of us back into the wall. The balloon was a standard round kids birthday party balloon. Making dangerous things with my Dad brings back memories...

Kipp

If it blew up like that, you didn't have 100% hydrogen inside. Pure hydrogen will not explode like that, and is also difficult to ignite. You could put an electric igniter inside a bag of 100% hydrogen and it would not do anything. Pure hydrogen does not even burn in the absence of oxygen. If you ignite a bag of pure hydrogen from the outside with an open flame, you will get a slow burn where the envelope is first burned away, which then increases in speed as more envelope melts away and the outside air mixes with the hydrogen escaping out the hole. The more oxygen there is mixed in with the hydrogen inside the bag, the faster it will burn. At 5% oxygen there is almost no noticeable difference. At 10% it burns with a woosh. At 20% you start getting into the explosive range. At 33% you get maximum explosive force with minimal activation energy-- even static sparks will set it off.

Here is a video of a balloon with 6% oxygen burning:
https://www.youtube.com/watch?v=iaXbeLah0iM

[pyronaught]

This is very cool. My son is interested in blimps and has asked me why he can't get hydrogen gas to experiment with. I'd love to build the 120V version. . . you WILL post complete instructions, pretty please??

Two thoughts:

(1) Farm it out to the MakerGear community. I'd be willing to print a few and mail them back to you. See how the "distributed server farm" idea works for 3D printers.

(2) If enough people build these things, you won't have to rant about the lack of hydrogen gas availability any more.

I can print six screen sets per day while doing other things. I have my printer next to my computer so it's not too big of a deal to be changing out a print every hour. The 120v unit requires 60 screens, so I'd have it done in 10 days. It will take about 3Kg of filament and $240 worth of stainless plates to make it though, so you are looking at over $300 in materials cost to build a 120v generator. And that's just for the cell, you'd still need about $100 or more in other parts, and if you want to run it for long periods then it will take a few hundred more dollars to add a cooling system for the electrolyte to keep it from overheating. So you'd have to REALLY want one to spend that kind of money. Since I'm using this for big RC blimps and will save $90 or more on helium per fill, it pays for itself pretty fast.

If you just wanted to make a Browns Gas generator (doesn't separate the gases) for the purpose of blowing stuff up in your backyard for the fun of it and not lifting balloons, that can be made a lot faster since you don't need the screens and a single frame per section can be used so your print time is cut in half. Just a few 12v cells would work fine for filling water bottles and milk jugs. Two liter bottles are so tough they actually turn into rockets instead of exploding. Milk jugs make a decent boom though. The 12oz water bottles are about as loud as a firecracker. All it takes for a detonator is a grill igniter, then you just put a metal rod in the ground and zip-tie a length of speaker wire to it where 1/4" the insulation has been stripped off the end to create a spark gap. The other end of the wire is connected to the grill igniter, then you just invert bottles onto the rod and click the button to set it off from a distance.

[pyronaught]

I volunteer to print a few as well !!! Seems like a neat idea and cool project !!! I have always wanted a giant balloon that was large enough to make me ...almost weightless. The idea of being able.to jump and float weightless for even a short time would be amazing !!!

I seem to recall seeing a video of someone who did this. Of course when you jump, you are always going to travel in the direction of the prevailing ground wind. Still it looked pretty fun.

Figure it will take about 16 cubic feet of gas per pound of lifting force. So if you wanted to reduce your weight by 100lbs, that would be 1600 cubic feet of gas. Consider though that even a single 120v generator cell can only produce about 5 liters of hydrogen per minute, which translates to about 10 cubic feet per hour. So you would have to run a single cell for 160 hours to fill your balloon! Of course you could build multiple 120v cells and run them in parallel, but you will probably exceed the current limit of your home wiring after about four cells. So best case if you had the money and patience to build four 120v cells it would take you two days to fill a 1600 cubic foot balloon. Electricity costs would only be about $20 though (at least where I live), so once you got past the big up front startup cost you could get some pretty cheap joy rides.

Now, if you wanted to run off 240v mains you could make something like the giant unit in the video link below. Those are Browns Gas generators in the video, but the setup would look exactly the same. You would just have to make six 120v generators to pull this off. But then you would be able to crank out hydrogen at the rate of 74 cubic feet an hour, allowing you to fill your 1600cf balloon in 21 hours.

https://www.youtube.com/watch?v=SL7l6S8ut_U

[sthone]

If it blew up like that, you didn't have 100% hydrogen inside. Pure hydrogen will not explode like that, and is also difficult to ignite. You could put an electric igniter inside a bag of 100% hydrogen and it would not do anything. Pure hydrogen does not even burn in the absence of oxygen. If you ignite a bag of pure hydrogen from the outside with an open flame, you will get a slow burn where the envelope is first burned away, which then increases in speed as more envelope melts away and the outside air mixes with the hydrogen escaping out the hole. The more oxygen there is mixed in with the hydrogen inside the bag, the faster it will burn. At 5% oxygen there is almost no noticeable difference. At 10% it burns with a woosh. At 20% you start getting into the explosive range. At 33% you get maximum explosive force with minimal activation energy-- even static sparks will set it off.

Here is a video of a balloon with 6% oxygen burning:
https://www.youtube.com/watch?v=iaXbeLah0iM

Sounds like It was probably the poor mans hydrogen that's made with liquid Drano. I use to play with that stuff as a kid and had similar explosive results.

-Steve

[Jules]

Would you boys please not blow yourselves up?

[pyronaught]

Would you boys please not blow yourselves up?

This stuff is pretty light weight compared to the explosives I normally play with.

[Jules]

Would you boys please not blow yourselves up?

This stuff is pretty light weight compared to the explosives I normally play with.

I know, but....remember the Hindenberg and all that..........