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Flared coaxial lip?

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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Flared coaxial lip?

Unread postAuthor: noob of noobs » Wed Jul 04, 2007 1:06 pm

This might sound a bit stupid, but you know how in a coaxial theres a barell inside a chamber? That air has to squeeze through a small barell, and if that entrance to the barell is small, cramming air into it could be a little hard.
For example, if you've ever used a blow pipe (you put a dart in one end of a pipe, then blow it out the other end) it's a lot harder to get adequate power without a mouthpiece. The mouthpiece works as a funnel, channelling the air and compressing it into more power.
Now suppose you were to put something like a mouthpiece on the back end of a barell in a coaxial. Suppose you flared the end using hot oil and a funnel. Would that help the barell get more air and transfer power from the chamber better, or is this just a stupid idea?

Thanks
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Unread postAuthor: pyrogeek » Wed Jul 04, 2007 1:52 pm

It would work, and I could see why it would be a good idea since that would also allow you to use a bigget piston/diaphram, resulting in higher air flow. Although, without a lathe, it may be hard getting the end nice and square so you get a good seal. Maybe a PVC fitting trimmed and glued on would work better it that was the case. Of course, that would be bulkier and obstruct air flow unless you trimmed it just right. Or, you could always just add a foot long section of larger diameter pipe on the end, even though that will be two more joints and the larger pipe won't typically be rated to as high a pressure.
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Unread postAuthor: noob of noobs » Wed Jul 04, 2007 2:02 pm

Thanks, I think I might try something like this on a shotgun me and my friend are making.
I'm not quite sure what you mean by trimming a PVC fitting. Do you mean something like a 1/2" to 1" adapter with the larger end cut down a bit?
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Unread postAuthor: hi » Wed Jul 04, 2007 2:19 pm

you could do that, but the problem is you would need farly large chamber.

normally a 1/2'' barrel in a 1.25'' chamber is fine, but with this you would probably need a 1/2'' barrel and a 2'' chamber.
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Unread postAuthor: boilingleadbath » Wed Jul 04, 2007 3:22 pm

My understanding is that the sharp turn does reduce flow some, so a flared end probably would help.

But, as others have said, it may be difficult to realize these modifications.
Perhaps one could use a coupling instead of thermoforming the PVC?

Alternatively, I have read that rounding the edges of the pipe back there helps flow as well.
(as an added benefit, the inside corner of the couplings are already rounded)
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Unread postAuthor: noname » Thu Jul 05, 2007 10:45 am

That's a pretty good idea, and when I first read it, I thought, Bell Reducer! The only problem is that DWV doesn't get small, so the minimum barrel would be 1 1/2"."
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Unread postAuthor: Modderxtrordanare » Thu Jul 05, 2007 6:20 pm

Couldn't someone follow the how-to on spudtech to make the flared tip on the rocket, then cut it real short and put a coupling on the "flat" end. Then attach that to the end of the barrel.


Just use an orbital sander to smooth down the face. Put the sander upwards in a vice and apply pressure along the entire face of the flared end onto the sander.
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Unread postAuthor: bigotry2 » Thu Jul 05, 2007 6:47 pm

Or you could flare the coupling instead, so you get unlimited tries?

Or, if you cut the barrel short a bit, put a coupling on it in the chamber, then take another piece of pipe and work on flaring that piece. (This is all just incase you're not an expert flarer, it gives you fail safe. 8) )
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Unread postAuthor: schismatized » Thu Jul 05, 2007 7:10 pm

hmm but then how would you shove taters in there if we did this??
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Unread postAuthor: sandman » Thu Jul 05, 2007 7:46 pm

just like we do now, i dont see any problem
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Unread postAuthor: Modderxtrordanare » Fri Jul 06, 2007 12:06 am

bigotry2 wrote:Or, if you cut the barrel short a bit, put a coupling on it in the chamber, then take another piece of pipe and work on flaring that piece. (This is all just incase you're not an expert flarer, it gives you fail safe. 8) )


That is exactly what I said to do. :wink:

schismatized wrote:hmm but then how would you shove taters in there if we did this??


We are talking about flaring the end that the piston seats upon, not the muzzle. (Being where you insert the potato/miscellaneous ammo.
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