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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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Unread postAuthor: Jimmy K » Fri Mar 04, 2011 5:49 pm

Yes, actually. I haven't really designed anything for that yet though. Still a little ways off.


Here's a video of the valve test.

About 10-15psi, one valve dump.

(I am sorry for the barking dog and otherwise awful sound quality)

[youtube]http://www.youtube.com/watch?v=BGXPzwBmpDc[/youtube]
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Last edited by Jimmy K on Sat Mar 05, 2011 11:40 am, edited 1 time in total.
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Unread postAuthor: Gun Freak » Fri Mar 04, 2011 6:42 pm

Not as big a bang as I expected... I though it would destroy that box :D
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Unread postAuthor: Jimmy K » Fri Mar 04, 2011 9:52 pm

It did blow a hole in the box actually. Ill make a video of the valves without the compressor going later.
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Unread postAuthor: Jimmy K » Tue Mar 08, 2011 3:19 pm

So I didn't have enough time to do more substantial work on the cannon, but I did rig the valve to shoot stuff out of a 3" by 30" makeshift barrel. I was shooting empty soda cans at 25 psi. The cans actually were crushed by the time they left the barrel.

[youtube]http://www.youtube.com/watch?v=lSFRbVCOAmc[/youtube]
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Unread postAuthor: mark.f » Tue Mar 08, 2011 4:46 pm

Jimmy K wrote:The cans actually were crushed by the time they left the barrel.


So fill them with water. :wink:
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Unread postAuthor: Technician1002 » Tue Mar 08, 2011 6:05 pm

Or turn them around so air pressure inflates the can.
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Unread postAuthor: Jimmy K » Tue Mar 08, 2011 6:29 pm

Alrighty. Time for a question.

I bought 4 of these and 2 of these to connect the valves to the 4" tee. Here's my question: is minimizing dead space imperative to good performance? I am inclined to leave the valves where they are because of the support from the metal pipe nipple out the bottom of each and because of the air tank versus having each valve sort of suspended by PVC fittings in between the tee and the metal nipple (acting as an elbow). Would I have noticeably worse performance with more dead space?
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Unread postAuthor: Technician1002 » Tue Mar 08, 2011 6:41 pm

Personally I wouldn't have bought the 45's. I would have made 2 long sweeps instead. I would go for minimum dead space with the barrel on a T with both valves right on the T. The T and barrel can be strapped to the tank for support.
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Imagine building with flow in mind. Try for something like this between the tank and valves;
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Unread postAuthor: Jimmy K » Tue Mar 08, 2011 6:49 pm

The two 45's can still be returned.

On making long radius sweeps: when you bend pipe, wouldn't there be a tendency to "fold" over or crease the pipe? And wouldn't the outside wall become thinner, thereby weakening the pipe?
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Unread postAuthor: Technician1002 » Tue Mar 08, 2011 6:57 pm

Long sweeps seem to work fine and are commercially sold. Kinks are an issue when bent too sharply. A long sweep is fine.
You don't find them in big box stores as they are rarely used in residential locations.


High pressure high flow applications use them in steel all the time You may see these used in city water, industry, an gas applications.
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Unread postAuthor: Jimmy K » Tue Mar 08, 2011 7:03 pm

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Unread postAuthor: Technician1002 » Tue Mar 08, 2011 7:11 pm

yes, but make your own. High pressure in steel is the norm for industry. It is commonly used in electrical because wires pull much easier into them.
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Unread postAuthor: Jimmy K » Tue Mar 08, 2011 7:40 pm

I could probably get a hold of some exhaust piping or other metal pipe in 180 degree or 90 degree sweeps, but I'm not so sure that'd be the most cost effective option. I am on a budget, believe it or not haha
Plus the metal would need to be thick enough to use a die on or to weld (arc, I only have access to an arc welder) without deforming the fitting.. I'm not positive but I think exhaust pipe is around a schedule ten.. so 1/8" walls (nominally).

How easy is bending PVC?
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Unread postAuthor: Technician1002 » Tue Mar 08, 2011 7:47 pm

Do you have a gas campstove? Gently heat it in a large area and avoid overheating. It will turn from rigid to pliable like a garden hose. Shape and let cool. For smaller stuff, a gas torch sitting on the ground can be used as a substitute. Again stay out of the flame. You are not doing decorative wood burning here. It's a slow roast to gently warm the pipe.

Practice with 1 or 2 inch stuff first to get the feel for it. Heat well above the burner in the rising hot air. Keep it moving and rotating. Stop heating any area that becomes soft and expand the heated area so the entire length of the bend area is soft. Shape and let cool.

Note, these guys got too close and browned the pipe in a couple of spots. Avoid that.

[youtube]http://www.youtube.com/watch?v=2Qs-PILTCbw[/youtube]
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Unread postAuthor: Jimmy K » Tue Mar 08, 2011 8:16 pm

Alrighty. Thank you. There's nothing like trying new things.
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