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PVC Meter - Just an idea that might work really well.

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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PVC Meter - Just an idea that might work really well.

Unread postAuthor: wangpushups » Sun Nov 04, 2007 7:04 pm

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How much PSI do you think this might hold? I personally only need around 30 - 50 psi. This might be a great idea if you dont want any extra weight and its cheaper and when you pvc weld all of it, you would have no leaks. This is just an idea, what do you guys think?
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Unread postAuthor: hi » Sun Nov 04, 2007 7:07 pm

i see no reson why it wouldnt work. it would look nicer if you built it out of metal pipe, but thats fine. i wouldnt solvent weld it to the chamber though.
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Unread postAuthor: wangpushups » Sun Nov 04, 2007 7:07 pm

You wouldnt have to thread or tap the chamber like you would with a metal meter and it would look cool cause its pvc and it would look natural on the gun,...just an idea though.
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Unread postAuthor: DYI » Sun Nov 04, 2007 7:17 pm

The diameter of the meter hole and the OD of the meter pipe would have to have VERY close tolerances and be perfectly smooth for the PVC solvent cement to work properly. I would recommend epoxy, or just threading it into the side of the pipe.
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Unread postAuthor: Pete Zaria » Sun Nov 04, 2007 7:17 pm

Well the answer to how much pressure can it hold is: as much pressure as the lowest-rated part can handle.

The problem isn't the pressure, it's the cold. Liquid propane evaporating to it's gaseous state (as we need it for spudguns) is a very endothermic process, and tends to cool the components involved. Cold PVC is brittle. The best way to avoid this would be to use a regulator, which shouldn't let liquid propane through anyway. On my gun, I use a jury-rig solution; two small loops of hose between the tank and the meter, to allow any liquid propane to evaporate before it hits the meter pipe.

Hope that helps.

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Unread postAuthor: Ragnarok » Sun Nov 04, 2007 7:28 pm

The idea could work, but meters are built in metal for quite a lot of reasons.

I also have to mention that solvent welding like that through two layers of PVC would be a serious weak point.
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Unread postAuthor: BigGrib » Mon Nov 05, 2007 5:38 am

I agree with DYI on the threading of epoxying the meter to the barrel definantly a safety issue. whats gonna happen if for some reason you bump that thing the wrong way and crack something and not know, fire that thing off and watch that meter seperate very violently from the barrel, or better yet blow up. Sorry just the pessimist in me. Other than that it is a good idea
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Yea, that's definitely going to get you at least a tazer.

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Unread postAuthor: Fnord » Mon Nov 05, 2007 9:27 am

The main volume of my old hybrids propane meter was pvc. Not only that, but I solvent welded the gauge into it, and didn't use primer on any of the fittings :) (the guage was made of some unknown black plastic)

There were no leaks, and the cold had no effect even though I may have gotten liquid propane in the meter once or twice. I was using 1/2" sch40 pvc.

In short, yes, it'll work, but I'd find a better way of attaching it to the chamber. Try a schrader valve+bicycle pump hookup. That way you can use the meter on more than just that gun.
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Unread postAuthor: jimmy101 » Mon Nov 05, 2007 10:38 am

You can omit the valve next to the regulator/pressure gauge if you have a valve on the propane tank.

Glueing into the chamber like you suggested is going to be tricky. You might want to consider tapping a hose barb into the chamber and installing one on the meter pipe. Then just use a short piece of pressure hose between the meter and chamber. You local hardware store should have 1/4" NPT male to hose barb fittings.

I don't think the temperature is going to be much of a problem, you won't be firing the gun fast enough for the meter to cool off. You really shouldn't even have any problems with liquid propane getting into the meter if you keep the propane cylinder upright. When I fuel with a plastic syringe the syringe shows no signs of cooling off when filled.
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Unread postAuthor: BigGrib » Mon Nov 05, 2007 6:19 pm

I still think you guys are crazy. I would use 3/4" Galvi Pipe and do the math on it for your pressure. Sorry it's just me but I prefer metal to make the meter.
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Yea, that's definitely going to get you at least a tazer.

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Unread postAuthor: Novacastrian » Mon Nov 05, 2007 7:24 pm

I like the design. Metal would be stronger but also heavier.
Defiantly a good idea for spudders that have no access to metal tube.
What i would do is fusion weld it onto the chamber, strong as :wink:
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