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Introduction and My First Pneumatic

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: Introduction and My First Pneumatic

Unread postAuthor: hectmarr » Wed Nov 06, 2019 9:11 am

I have this drawing of a pressure regulator to share.
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Ideas don't make holes, guns do!
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Re: Introduction and My First Pneumatic

Unread postAuthor: jackssmirkingrevenge » Wed Nov 06, 2019 9:34 am

SloppyJoeES wrote:Chicken :wink: :bom:


Far from it, Moonbogg is just acutely aware of potential material failures and their negative consequences, and on this forum definitely the one who goes the furthest to make sure nothing is left to chance, which is laudable in my book.
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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: Introduction and My First Pneumatic

Unread postAuthor: mrfoo » Wed Nov 06, 2019 3:19 pm

Any ideas for removing those damn screws? They're in there good!

The trick I use for removing recalcitrant and buggered allen screws is:

Take a drill-driver bit of the correct size, put it in the remains of the hole. Using a pin punch, carefully peen the remains of the head around the driver bit, thus re-forming the hex. Then, without removing the bit, hit it with your drill driver on maximum torque. This approach is very effective on small steel bolts (m5, m6) corroded into alu, as the act of peening over "shocks" the threads free , more or less. Throw away the bolt once you've done, obvs.

Not sure if this will work on screws you've simply over-torqued.
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Re: Introduction and My First Pneumatic

Unread postAuthor: Moonbogg » Wed Nov 06, 2019 6:53 pm

jackssmirkingrevenge wrote:
SloppyJoeES wrote:Chicken :wink: :bom:


Far from it, Moonbogg is just acutely aware of potential material failures and their negative consequences, and on this forum definitely the one who goes the furthest to make sure nothing is left to chance, which is laudable in my book.


I do the best I can, but also my nano-suit went missing so I have to protect my frail human form using preventative measures instead.
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Re: Introduction and My First Pneumatic

Unread postAuthor: D_Hall » Sat Nov 09, 2019 11:51 am

jackssmirkingrevenge wrote:Most commercial pneumatic air rifles operate in the 2000-3000 psi range, nothing wrong with higher pressures as long as they are safely contained. In a QEV designed for 150 psi though, it is bordering on suicidal.


Fixed that post for ya.
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Simulation geek (GGDT / HGDT) and designer of Vera.
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Re: Introduction and My First Pneumatic

Unread postAuthor: jackssmirkingrevenge » Thu Nov 14, 2019 7:33 am

D_Hall wrote:Fixed that post for ya.


Eh, teen subculture these days seems to be all about that, at least they're being creative about it.
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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: Introduction and My First Pneumatic

Unread postAuthor: SloppyJoeES » Sun Nov 17, 2019 9:04 pm

Although taking fittings outside their ratings, especially to such an extreme degree, is inherently dangerous, I don't see this is particularly suicidal. I am well outside the burst pressure for any component and the only thing I can see getting easily destroyed is the diaphragm in the QEV, which would simply cause a constant stream of hpa tank to come through the batrel until the hpa ran out or I turned it off, and fire whatever projectile may have been in the barrel I'm the process.

Not condoning this kind of behavior, but I don't see that huge of a risk to my own health taking place here, so much as I place as much respect on the launcher as I might a firearm.

Anyway, I am indeed switching to something a little less crazy, which will output 450psi. Until the parts that will allow me to do that come in however, I have finally decided to make my own clone of one of my favorite projects on the site, jack's pen gun.

Its going into a 8mm od 6mm ID tube made of 304 stainless steel. The barrel will be a 1/8" annealed aluminum tube made by K&S I got from Ace. I plan on moulding a piston out of hot glue, onto which I will adhere a 3/16" thick piece of gasket rubber to be the sealing face.

I say 'adhere' because I have no idea how to stick this thing in best... I already tried making one of these in a 1/4" pipe nipple with a piece of 1/4 copper tubing as a barrel and the same piston setup described above, but with the rubber glued on with superglue. The superglue made the rubber kind of stuff, so I thought maybe that's why it won't seal well. I also have guessed that there may have been an issue using threaded pipe fittings as the chamber, as the threads may have interfered with the seal, but honestly I have no idea. This projects got me feeling DUMB so far...

My new one will be done with a lot more care, so hopefully I am more successful. Any advise on my piston and how to make the pen gun work properly? I understand how it works fine.
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Re: Introduction and My First Pneumatic

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Re: Introduction and My First Pneumatic

Unread postAuthor: jackssmirkingrevenge » Mon Nov 18, 2019 7:19 am

SloppyJoeES wrote:Although taking fittings outside their ratings, especially to such an extreme degree, is inherently dangerous, I don't see this is particularly suicidal. I am well outside the burst pressure for any component and the only thing I can see getting easily destroyed is the diaphragm in the QEV, which would simply cause a constant stream of hpa tank to come through the batrel until the hpa ran out or I turned it off, and fire whatever projectile may have been in the barrel I'm the process.


The assumption you're making here is that there isn't some flaw in the components that would reduce the actual burst pressure, it's important to be aware of the risks especially with parts manufactured to a price.

SloppyJoeES wrote:I plan on moulding a piston out of hot glue, onto which I will adhere a 3/16" thick piece of gasket rubber to be the sealing face.


Hot glue is a bad idea if you plan on taking it to significant pressure. Consider epoxy instead.
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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: Introduction and My First Pneumatic

Unread postAuthor: SloppyJoeES » Tue Nov 19, 2019 10:35 pm

I have had great difficulty casting a piston for the pen gun. My problems mainly arise with pouring and removing the materials I have tried so far. I was only able to remove my hot glue piston once. The second time, I tried to remove the hot glue from the pipe section I casted it in and it was stuck with no hope of getting it out without destroying it.

I have also used JB Weld, both on its own and mixed with a minute amount of acetone to water it down.

Each time I used vegetable oil and Pam to try and keep the stuff from sticking. At this point, I almost feel like giving up or trying something larger. Maybe a thick rubber sheet cut to size would work well instead.
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Re: Introduction and My First Pneumatic

Unread postAuthor: jackssmirkingrevenge » Wed Nov 20, 2019 7:05 am

SloppyJoeES wrote:Maybe a thick rubber sheet cut to size would work well instead.


I can confirm that it works. For casting you really need the right materials and I find that marine epoxy works best as per the guide posted previously.
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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