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Propane + Oxygen + Steel Gun

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Propane + Oxygen + Steel Gun

Unread postAuthor: xequa » Wed Mar 17, 2010 1:42 am

Hi folks, I'm trying to design a steel potato cannon that uses propane and a bit of O2 to generally increase the % of available combustible matter in the chamber.

While I would love to ramp the thing up to something insane like 5x mix of O2 to create a giant boom (remotely of course), I understand that more O2 means lots more heat. That won't do, so I'm comfortable for using O2 as a shortcut through the venting process and also as a bit of .. steroids for propane, if you will.

First, any opinions on this?

Second, where ON EARTH do I find an adapter to get the gas out of this Bernzomatic cylinder? I've had zero luck in finding a left hand turn adapter or anything of the like. The idea was send in the metered propane, then send in the metered o2, detach meter, mix, boom, repeat.

Your input is much appreciated, thank you.

x
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Unread postAuthor: grock » Wed Mar 17, 2010 2:43 am

well, using O2 isnt real safe, but with remote detonation and steel, should be fine. depending on the remote distance, you might want t wear hearing protection. as for an adapter, some people take a torch with a hose, cut the hose and get a hose barb, then thread the hole they are putting it into. you could also try to use something off this page, if you don't want to shred a torch.

EDIT: actually, you say meter, detach, boom, repeat, if you used one-way valves, you wouldn't even have to detach. in fact, if you rigged something like a double solenoid valve on each the propane and the O2, you could do more like boom, push 2 buttons, repeat
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Unread postAuthor: CS » Wed Mar 17, 2010 2:48 am

Combustion cannon discussion ---> Hybrid cannon discussion

Do you understand the "x" variable is according to one atmosphere? At sea level 14.7 PSI, 20.9% of which is Oxygen.

Possible you've considered it, but why not use compressed air to deliver the oxygen?

Image

^I've never seen the oxygen side sold separately, but I've seen kits like above for $80-100 at Home Depot and Lowes. (torch not in picture)

More details about the project?
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Unread postAuthor: deathbyDWV » Wed Mar 17, 2010 8:27 am

I got my oxygen adaptor in a torch kit at a store called Atwoods. It was only $50 there.
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Unread postAuthor: metalmeltr » Wed Mar 17, 2010 8:41 am

Home Depot, lowes, Menards ect carry oxygen/ MAPP gas torches that go for about $50.
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Unread postAuthor: Moonbogg » Wed Mar 17, 2010 12:52 pm

I made an O2/MAPP cannon, and above all else I can promise you that it is retardedly expensive to operate. The O2 runs out fast and it costs 10 bucks a bottle. Secondly, it produces a lot of heat which just absolutely loves to melt anything thats not metal. This includes ignition wires, rubber bumpers, fans etc. I say go with air. The only challenge with air is you need an air tight chamber that can stay sealed at a few atmospheres. But air is free.
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Unread postAuthor: xequa » Wed Mar 17, 2010 8:48 pm

Wow folks this is very useful information... your experience has forced me to reconsider the project in total! It sounds like O2 is neat on paper, but it appears to be far from practical.

Details of the design, some of which would further suggest that O2 would be a bad move:

Pipe materials are to be black steel, threaded & sealed with whatever thread seal goop sounded best.

3" chamber with a cleanout at the end, then a 3 x 2" coupling, then two elbows to swing the flow up over the chamber, 2 x 1.5" reduction coupler, barrel.

Muzzle loaded.

JB weld some steel strapping to the inside of the chamber and mount a fan on it. Use very powerful magnets and actually mount a taser inside the chamber.

Run a spark gap loop around the inside.

Power the fan and the taser via running leads to spark plugs installed along the side of the chamber (or perhaps in a 2" section behind the reduction coupling). The taser would operate via controlling the power to the unit, not the high voltage current itself.

All the electronics would meet in a project box outside the chamber. They include a safety for the momentary trigger (located on a handle attached below the chamber and barrel) & a fan switch with an LED for when it's running. Probably need an adjacent project box for the batteries.

Fuel would be added to the chamber via a tap & ball valve on the side of the chamber, on the end of which would be a pneumatic tool quick release. This would let me mix gas in a separate meter/regulator assembly that I could attach/detach to the loading point, allowing me to free up space and reduce the clumsiness of its use. I'd also use that port for venting out exhausted gas, since the cleanout cap would be cumbersome to move after each shot.. and now that O2 is ruled out both by cost and consequences.

Just starting the thinking on this now after hearing your thoughts on O2, but perhaps I'd even help venting out with a hairdryer down the barrel.. lol kinda ghetto.

So why not a Hybrid? Honestly... I'm intimidated by their complexity and cost. Once I learned that those O2 torch assy's are around $50, I decided that alone was enough to drop it. Also, not sure how to manage a burst disc system effectively without doing heavy custom design (which is usually expensive too).

This revamped/reduced concept brings it back down to earth as just a normal potato cannon. I may use mapp instead to get the punch I was dreaming of, but I think the real glory of this steel beast will still be that I can launch very heavy things from it without worrying about blowing up the gun. Black steel pipe is rated for around 6,000 PSI, and my neighbor, who assembles GIANT rock grinders at quarries around the country (which requires welding of much black steel pipe for lubricants, steam, etc), says he's put 10k PSI through the stuff without event, which is kinda reassuring.

I hope I made this easy to read, and thank you for making it all the way to end, LOL!

RJS
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Unread postAuthor: Moonbogg » Thu Mar 18, 2010 3:57 am

If you are using steel pipe, all you need to do is find a way to hook up a cam lock and VOILA, instant hybrid! A hybrid does not have to be intimidating at all, especially at low mixes. It is just a regular combustion with some compressed air and extra fuel. If its steel, it would be strong enough.
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Unread postAuthor: xequa » Thu Mar 18, 2010 9:32 am

Pardon the thickness of my skull.... but how does a cam lock help keep the good stuff in? Where is it situated in the cannon?

Also, compressed air usually implies a compressor. But something silly and portable like a bike tire pump could work too, no?
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Unread postAuthor: CS » Thu Mar 18, 2010 12:16 pm

xequa, Spud Wiki - Burst Disk. No a specific picture, but the union picture should give you reference.

Depending on your mix you'll need to pump 15, 30, 45, ... PSI in the chamber. Your chamber size will determine how long this will take. Would be best if you had an electrical compressor that has a reservoir. Manually don't expect to get very far, very fast.

Also since your using far less Propane to compressed air, inject the Propane first and pump the air in afterward to better mix the two.

Steel is a great material, cheap, and easy to weld.
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Unread postAuthor: Moonbogg » Thu Mar 18, 2010 2:41 pm

I have a 300cu in chamber on my hybrid. Its about as big of a chamber as most full size combustion cannons. I can fill a 2x mix with a tiny little hand bike tire pump in like 45 strokes. It takes like 30 seconds. The camlock clamps together and usually is installe dby the barrel. Look at my signature cannon "cobra venom" and you will see how this one is installed. Better yet, look at Starman's "triple thunder" cannons. He has detailed posts showing how to use a camlock with a combustion cannon. If his cannon was steel, it could be used as a hybrid. You can still use chamber fans with low mix hybrids. Mine has survived hundreds of 2x shots and several 3x shots. Its a bigass 80mm PC fan.
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Unread postAuthor: xequa » Thu Mar 18, 2010 11:27 pm

Any suggestions on how to make this thing cheaper? 3" black steel pipe is very expensive... at this point I'll have to wait to build the thing till... "later."

Moon & CS, I'm lovin your information :) I'm not nearly as intimidated by hybrids now... just gotta figure out how to afford the thing!

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Unread postAuthor: Moonbogg » Fri Mar 19, 2010 12:34 am

xequa wrote:Any suggestions on how to make this thing cheaper? 3" black steel pipe is very expensive... at this point I'll have to wait to build the thing till... "later."

Moon & CS, I'm lovin your information :) I'm not nearly as intimidated by hybrids now... just gotta figure out how to afford the thing!

x


cheaper...Yeah. Make a parts list and go hunting! Seriously, go looking for the parts you need from dumps, junk yards or maybe even ebay. Anywhere you can find used parts, even if they are rusty, that will save tons of money. You can easily sand and clean the parts and they will look better than new.
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