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"realistic" fire

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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"realistic" fire

Unread postAuthor: battlelava » Thu Feb 09, 2012 1:24 pm

Hey haven't been on in a while but I'm starting to build a combustion after figuring i can't make my flak 88 just yet (not given up). What im trying to do is give my combustion cannon an "authentic feel" when i fire it. What im going to do is put a "primer" into it . So I took some used 22 rounds to make into a spark gap and have a hammer "hit" it to complete the circuit, my only problem is I don't have access to much metal or machinery and I was going to use a wood block but i have a feeling it wont be strong enough. was thinking about wrapping it with some type of thin steel i have laying around. any thoughts on how it might workout. i would also have to work out a way to get wood to glue to pvc. sorry for lack of grammer i have no time to write this right now :shock:
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Unread postAuthor: Daltonultra » Thu Feb 09, 2012 2:01 pm

You're talking about using a spent brass, right? So it will look like a primer being used to set off a charge?

I think we'd need to see at least a rough drawing of how you want to mount it before we could really judge.
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Unread postAuthor: battlelava » Thu Feb 09, 2012 2:58 pm

That's exactly what I'm doing I can get a rough sketch up in a little.

PS. I was going to use spent ..22s from a powder actuated gun slightly different in shape but same effect
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Unread postAuthor: battlelava » Thu Feb 09, 2012 5:21 pm

i tried to do a rough sketch and needless to say it is very very rough but Ill do my best to explain it i left out the firing system as I'm more concerned with the actual casing holder not blowing out. Here are a few pictures for reference
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I just found these two metal "bars" I guess you can call them for lack of better terms. No idea what type of metal they are, I got them when i took an old air-soft gun apart. All i can say is that there heavy. Maybe if i can determin the metal I could drill them out and solder them in (should be ok for a combustion I would think)
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Unread postAuthor: Daltonultra » Thu Feb 09, 2012 8:57 pm

Interesting. They look like an aluminum recycling ingot. When I was eleven, I got to see what a trailer full of those could do to a cab-over truck when it slammed head-on into a bridge pier. Not pretty...


Anyway, if you're worried about the brass getting blown out, you can use a hole that's slightly shallower than the brass, and mushroom the end out from the inside. The lip should be enough to hold it in place.
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Unread postAuthor: battlelava » Thu Feb 09, 2012 9:36 pm

Do you think it would be better to go all metal instead of mixing pvc wood and metal parts. Only problem i have with that is then I only have access to solder until I can get my brazing setup fixed. My soldering is as strong as it gets so it should hold up against a normal combustion as far as I know.

EDIT: I also forgot to mention the shell has to be removeable because I was also going to use it as a fueling port, hence why I was thinking of a sliding block to put behind it.
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Unread postAuthor: warhead052 » Thu Feb 09, 2012 10:13 pm

Solder will hold up to quite a bit, don't be afraid of a simple combustion. Just as long as you let it cool down a bit in between shots so it doesn't melt the solder.
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Unread postAuthor: battlelava » Thu Feb 09, 2012 10:20 pm

I wan this thing to be really strong because I'd rather not be picking out brass casings from my body :shock: I'm going to drill out those metal bars which I have determined to be either iron or steel based on how magnets will stick on them. Bummer its not something weaker. I'll post some pictures tomorrow.

Just wondering how much pressure do you think will be applied to the casing and since a majority I would think would be going out the barrel.
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Unread postAuthor: Zeus » Fri Feb 10, 2012 3:11 am

Look, a simple combustion will never exceed ~100psi if you use propane/butane. So I have to say this.

IT WON'T BLOODY EXPLODE.

A .22lr shell handles about 20,000psi, nothing can happen. If you're worried about the solder melting, then don't fire it until your fingers start smoldering.

This ridiculous idea that people have, that combustions are more dangerous because flames and hollywood special effects, is utterly stupid, and should be ignored.
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Unread postAuthor: jackssmirkingrevenge » Fri Feb 10, 2012 4:03 am

Wait what?

Are you going to use a 22 cartridge as a combusion chamber?

If so, expect the equivalent power of an tardigrade sneeze...
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Unread postAuthor: battlelava » Fri Feb 10, 2012 9:33 am

I'm not worried about it exploding I just don't want the brass to launch out the back and the brass is not a chamber. I wanted to make it really strong invade I was to make it a hybrid somewhere down the road

PS I don't get this from Hollywood
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Unread postAuthor: Fnord » Fri Feb 10, 2012 9:49 am

Take the bore surface area of a .22 casing and multiply it by the maximum chamber pressure, and it comes out to around 4 pounds. If it takes more than 4 pounds to dislodge the casing, you'll be fine. Any el-cheapo five-minute epoxy would hold it in place without any trouble. You could probably wedge it in a tight fitting hole with no glue at all and it wouldn't come out.

Even if it does, you'll get hit with less than 4 inch-lbs of kinetic energy, which might be dangerous if it hits you in the eye, but otherwise getting shot by a rubber band will probably hurt more.
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Unread postAuthor: battlelava » Fri Feb 10, 2012 12:12 pm

Thanks fnord. That was my actual concern. I'm thinking about a quick release cover (thanks to having boring classes) so he shells will be exchangable for whatever reason that Comes up.
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Unread postAuthor: battlelava » Sat Feb 11, 2012 12:20 am

So I just thought of something of major importance safety wise. I need to find a way to prevent a live casing from being used (not trying to break any rules bringing it up), personally I'm smart enough not to but I don't need someone trying to slip one in for a bigger bang, not that the fake hammer could set it off with how lightly it will tap but perhaps the electrical current might depending on where it arcs? I would rather not find out how 25k psi (or whatever it gives) acts in a pvc or thin walled metal cannon designed for 100 psi. :shock: :withstupid:
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