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Acetylene

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Re: Acetylene

Unread postAuthor: farcticox1 » Wed Jun 19, 2019 4:34 pm

They do look awesome, very scifi, sort of Flash Gordon.

codyraygun.jpg
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Re: Acetylene

Unread postAuthor: D_Hall » Wed Jun 19, 2019 9:48 pm

Moonbogg wrote:I see the appeal of acetylene. It's easy to fuel the cannon with a basic atmospheric mixture while still getting good power from it.


Not really.

Once upon a time a certain someone (not me!) actually did a government study on the best gases to use for such applications. They studied (from memory) hydrogen, methane, ethane, propane, butane, and yes, acetylene. What they found was that the performance differences were small. After all, if you're mixing with air you've got a limited amount of oxygen so that's going to keep all hydrocarbons in the same performance ballpark (and hydrogen too, it turned out). After they spent a fair chunk of change they came to the same conclusion that I did before they even started....

"Its tough to beat propane for the combination of performance, cost, safety, and ease of use. If propane doesn't give you enough performance, using a bigger combustion chamber is a much better route than using weird fuels."
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Re: Acetylene

Unread postAuthor: Moonbogg » Wed Jun 19, 2019 10:27 pm

D_Hall wrote:
Moonbogg wrote:I see the appeal of acetylene. It's easy to fuel the cannon with a basic atmospheric mixture while still getting good power from it.


Not really.

Once upon a time a certain someone (not me!) actually did a government study on the best gases to use for such applications. They studied (from memory) hydrogen, methane, ethane, propane, butane, and yes, acetylene. What they found was that the performance differences were small. After all, if you're mixing with air you've got a limited amount of oxygen so that's going to keep all hydrocarbons in the same performance ballpark (and hydrogen too, it turned out). After they spent a fair chunk of change they came to the same conclusion that I did before they even started....

"Its tough to beat propane for the combination of performance, cost, safety, and ease of use. If propane doesn't give you enough performance, using a bigger combustion chamber is a much better route than using weird fuels."


I wouldn't feel safe using acetylene, nor would I feel it necessary for more performance myself, but my source of confusion is coming primarily from this article.

https://www.technologyreview.com/s/5146 ... elocities/

Not sure how credible it is, but it suggests acetylene is significantly more powerful. Regardless of the power situation, I think the OP may have mentioned making his own acetylene gas, or someone mentioned it in this thread. That sounds horrendously dangerous to me personally and I'd actually beg the OP to just not try doing that.
What are your thoughts on the claims made by this article?

If I ever felt like a gas cannon wasn't powerful enough for me, I'd just build a traditional cannon the old fashioned way and shoot bowling balls or something of that sort. I actually find traditional cannons to be kind of boring compared to our propane creations. It's too easy the traditional way. Getting power from propane takes creativity. It's fun.
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Re: Acetylene

Unread postAuthor: D_Hall » Thu Jun 20, 2019 12:00 am

First off, the article is clearly referencing a paper from the USAF Academy. Translation? It's a student lab project. Results are nice, but aren't necessarily expected to be definitive. It's an exercise, nothing more.

That said, I suspect the results have more to do with the ease of getting a good reaction with acetylene (detonations make things easy) than anything else. I would question how they were controlling their fuel/air mixture, inducing turbulence (a smooth walled spud gun of small scale is going to have flame propagation rate issues), and what their igniter system/placement was.

Of course, there's something to be said for ease of use and I concede that in my experience precision is much more important so I (and those I associate with) tend to ignore that aspect, but the energy of combustion per oxygen available (which is essentially fixed) doesn't vary that much.

Or maybe I'm full of crap. Regardless, I'd want to see their experimental setup before I drew too many conclusions.
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Re: Acetylene

Unread postAuthor: Moonbogg » Thu Jun 20, 2019 12:25 am

All I know is we live in different times. They used to sell a toy cannon that worked by putting calcium carbide grains in it with some water. Advertised in comic books to kids. Imagine that today? lol, nope.

https://en.wikipedia.org/wiki/Big-Bang_Cannon

OMG! You can still buy them, lol. I can't help but feel silly for freaking out about "making your own acetylene". I didn't know this was a thing. It's definitely a thing. Still a dangerous thing though.

https://www.bigbangcannons.com/
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Re: Acetylene

Unread postAuthor: mobile chernobyl » Thu Jun 20, 2019 11:12 am

Moonbogg wrote:
farcticox1 wrote:so they are a thing :shock:



I don't like this at all. These guys have beautiful cannons and they appear to know what they are doing. I thought we were special. I thought I was special. Seeing those guys with those beautiful cannons feels like I just saw someone with my wife or something. I need to start a therapy thread or something.
These guys in the video are badasses. They tame dangerous fire and make it do stuff they want. They are true human. There is hope for me in this hobby in my older years (as long as I don't die young from taking an aluminum end cap to the face).
I see the appeal of acetylene. It's easy to fuel the cannon with a basic atmospheric mixture while still getting good power from it. However, I can't see myself moving away from hybrid cannons. Propane and air mixtures can practically deliver as much power as you can build for and manage to compress in the chamber. My heart is with the propane powered hybrid cannons. I can't wait to build another one.
Seriously, I bet a decent volume 4X piston cannon would out perform those acetylene cannons. You'd need to bring a big air tank with you though, but that would just replace their acetylene tank. The propane tank is so small it doesn't even count. :D


I just wanted to quote this so I could reply and say that you summarized all my feelings exactly haha. I live out in CO now - haven't made a spudgun in years but one of my dreams is to help the avalanche mitigation industry possibly with a more portable round launcher using hybrid construction vs. 600psi of nitrogen with heavy Size K or T gas cylinders. It will always be a dream of mine haha.
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Re: Acetylene

Unread postAuthor: Moonbogg » Thu Jun 20, 2019 11:43 am

mobile chernobyl wrote:
Moonbogg wrote:
farcticox1 wrote:so they are a thing :shock:



I don't like this at all. These guys have beautiful cannons and they appear to know what they are doing. I thought we were special. I thought I was special. Seeing those guys with those beautiful cannons feels like I just saw someone with my wife or something. I need to start a therapy thread or something.
These guys in the video are badasses. They tame dangerous fire and make it do stuff they want. They are true human. There is hope for me in this hobby in my older years (as long as I don't die young from taking an aluminum end cap to the face).
I see the appeal of acetylene. It's easy to fuel the cannon with a basic atmospheric mixture while still getting good power from it. However, I can't see myself moving away from hybrid cannons. Propane and air mixtures can practically deliver as much power as you can build for and manage to compress in the chamber. My heart is with the propane powered hybrid cannons. I can't wait to build another one.
Seriously, I bet a decent volume 4X piston cannon would out perform those acetylene cannons. You'd need to bring a big air tank with you though, but that would just replace their acetylene tank. The propane tank is so small it doesn't even count. :D


I just wanted to quote this so I could reply and say that you summarized all my feelings exactly haha. I live out in CO now - haven't made a spudgun in years but one of my dreams is to help the avalanche mitigation industry possibly with a more portable round launcher using hybrid construction vs. 600psi of nitrogen with heavy Size K or T gas cylinders. It will always be a dream of mine haha.


I went 10 years without building a spud gun and I honestly thought I was done with it. Then I got bit by the bug. It was incredible fun building a new cannon. I think you should make something.
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Re: Acetylene

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Re: Acetylene

Unread postAuthor: jackssmirkingrevenge » Sat Jun 22, 2019 4:40 am

Moonbogg wrote:I went 10 years without building a spud gun and I honestly thought I was done with it. Then I got bit by the bug. It was incredible fun building a new cannon. I think you should make something.


There is a certain primal joy in launching something at speed. I think it's intrinsic to our species, humans are uniquely adapted for throwing and finding mechanical means to enhance this has been a preoccupation of man for millennia. Indulging this predisposition is a source of happiness, along with a general focus on upper body strength as a man.
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Re: Acetylene

Unread postAuthor: Moonbogg » Sat Jun 22, 2019 7:40 pm

jackssmirkingrevenge wrote:
Moonbogg wrote:I went 10 years without building a spud gun and I honestly thought I was done with it. Then I got bit by the bug. It was incredible fun building a new cannon. I think you should make something.


There is a certain primal joy in launching something at speed. I think it's intrinsic to our species, humans are uniquely adapted for throwing and finding mechanical means to enhance this has been a preoccupation of man for millennia. Indulging this predisposition is a source of happiness, along with a general focus on upper body strength as a man.


That sounds very true. There really is something about it that is just damn fun. Today I shot 36 mini soda cans. I found a better spot in the desert where I have room to aim high and just let it rip (something I've been dying to do) and holy crap do those cans fly like crazy. It was insane how far and high they went, lol. I have video but it's nothing special. Just me shooting up into the air. Also, when those golf balls happen to not spin and hook during flight but go straight instead, I swear it looks like they just go for ever. No sign of dropping when they actually go straight. Crazy fun. If you know of a way to control spin or eliminate it (thin sabot or cloth maybe?) let me know.
My small barrel is begging for a heavier round. I have to find a way to make a heavier round the size of a golf ball. A mini tennis ball filled with cement or something like that would be incredible.
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Re: Acetylene

Unread postAuthor: D_Hall » Sat Jun 22, 2019 8:30 pm

Moonbogg wrote:If you know of a way to control spin or eliminate it (thin sabot or cloth maybe?) let me know.


Take a #10 or thereabouts wood screw maybe 1.5 inches long or so - the kind you might use on a deck - and screw it into the ball so that it sticks out an inch. Put that in your barrel so that the screw is a tail of sorts. It will stop the ball from spinning in the barrel and once clear of the barrel, life is good.
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Re: Acetylene

Unread postAuthor: Moonbogg » Sat Jun 22, 2019 10:35 pm

D_Hall wrote:
Moonbogg wrote:If you know of a way to control spin or eliminate it (thin sabot or cloth maybe?) let me know.


Take a #10 or thereabouts wood screw maybe 1.5 inches long or so - the kind you might use on a deck - and screw it into the ball so that it sticks out an inch. Put that in your barrel so that the screw is a tail of sorts. It will stop the ball from spinning in the barrel and once clear of the barrel, life is good.


Sounds like a good idea. I might actually try that. I might drill a hole first and use a nylon or similar screw. I don't want the metal screw to ding up and scratch the aluminum barrel.

EDIT: OMG I bet I can find some dart tails and screw them on to the golf ball or something like that! You know like throwing darts. I'm sure you can buy some extra tails and they might be hollow and can be screwed onto the golf ball. Wow that should really fly.

EDIT: Nah. The screw idea is better. Fins are too much work for a golf ball projectile and probably won't make much difference beyond using a screw.
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