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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: x2percentmilk » Sat Oct 25, 2008 5:35 pm

Hey, i just finished my first air cannon today, built similar to the one here
http://www.corin.com/bill/paintball/aircannon/
i used a 2 inch barrel and chamber, 3/4 solenoid sprinkler valve, cement, etc.

i could only get it up to 70 psi with the crappy bike pump i have, but even at that level i figured the range would be decent. With newspaper wadding i could only get a potato to go about 50 feet. Without the wadding it was more like 10-15.

I tried a golfball wrapped in a sock, a fit that was so tight i had trouble pushing it into the barrel, and it made it about 20.

is this normal? if not anything i should check off the bat?

thanks
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Unread postAuthor: Demon » Sat Oct 25, 2008 6:01 pm

The problem is the anti-siphon sprinkler valve, buy a 1 inch inline one and put elbows.You could still use your "old" solenoid and put it in the new valve because you surely dont wanna re-make you battery system.

And putting wadding should not,normally,increase the range of a potato because when you load the potato correctly, it makes a really thight fit.

A innapropriate loading could be the cause too.
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Unread postAuthor: x2percentmilk » Sat Oct 25, 2008 6:12 pm

thanks for the response :)
i forgot to include the details, i did actually use an inline with elbos, i had forgotten that he used a 180.

besides the potato, i used a golfball wrapped in a sock twice, with a really tight fit, as well as a shaved down nerf football that fit really tight.

the thing "feels" underpowered too, im not sure whats up. ive checked for leaks using soapy water. i found one on the threads from the chamber fitting to the valve brass fitting, and one where a reducer is in a T for an air pressure gauge.

both leaks were so small i couldnt even notice the needle moving, and because theyre in the chamber i cant imagine it affecting how much air gets to the barrel.
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Unread postAuthor: Demon » Sat Oct 25, 2008 6:22 pm

Golfballs in a sock are not a good idea because when the fit is too much tight then you cannot put your ammo in the barrel, there will be too much friction.

ive checked for leaks using soapy water. i found one on the threads from the chamber fitting to the valve brass fitting, and one where a reducer is in a T for an air pressure gauge.


You used a metal sprinkler valve?

And using a pressure gauge make it more akward to shoot, fragile and add leaks, there is a pressure gauge on your bike pump,use it.

A good spudgun with a non-modded sprinkler valve should loose max.1 PSI by hour (it is possible, all my spudgun do that)

And finally, if you didn't did, use a tire bike replacement valve, makes 0 leaks.
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Unread postAuthor: iisthemuffin » Sat Oct 25, 2008 6:24 pm

Post a picture of your cannon please. It amy be easier to tell if something is wrong if we could see it.
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Unread postAuthor: Demon » Sat Oct 25, 2008 6:25 pm

I agree with Iisthemuffin, post picture of it please.
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Unread postAuthor: x2percentmilk » Sat Oct 25, 2008 7:03 pm

alright, my camera's at school and i wont be back till tomorrow night, but ill post pics then

thanks guys, glad this place is so helpful
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Unread postAuthor: x2percentmilk » Sat Oct 25, 2008 9:00 pm

im wondering if the loud honk noise the gun makes is the problem. it honks like a banshee, hurts my ears, but i cant tell if its the valve or just the air coming out of the pipe (like an instrument)

im reading around and id really like to use the solenoid still...but if i cant ill make the sacrifice.

changing valves completely could be an option, but it would involve alot of cutting (ack)
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Unread postAuthor: potatoflinger » Sun Oct 26, 2008 11:08 am

Sounds like the valve isn't piloting, so that means that you should mod the valve to get good performance, but that also means that you won't need the solenoid.
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Unread postAuthor: iisthemuffin » Sun Oct 26, 2008 11:41 am

Open up your valve and give the diaphragm a nice cleaning under some water.
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Unread postAuthor: Demon » Sun Oct 26, 2008 12:12 pm

The sound may be cause by the big(2 inches) and irregular end of the cannon (if you sawed it with a handsaw).

Put a coupling, it will maybe reduce the honk.(i know it, i use a 1 inch
ballvalve in the same condition and it was making a strang sound)

What i reccomend you to do(if you didn't)

make a sharp end, will get 50%more range, 100% if you suck (for potatos only)

Reduce the barrel diameter, buy a 1.5/1.25 barrel because the 2 inch is a little bit too much for a un-modded sprinkler valve.

And please,post a picture...it will help a lot.
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Unread postAuthor: x2percentmilk » Sun Oct 26, 2008 5:59 pm

thanks everyone :) i ended up modifying the valve to work with a blowgun rather than the solenoid, epoxied everything up and WOW.

at 65psi the thing shot clean over a baseball field, ripped through trees, and even has a little bit of kick to it.

next step: making it a net gun :D

EDIT: when you say sharpen the barrel, do you mean file the outside down or file the inside down, or both?

heres a pic, the gap between the barrel looks bigger in the pic than it really is, and i might make some ammo holders or something similar to sit in there.
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Unread postAuthor: iisthemuffin » Sun Oct 26, 2008 6:05 pm

looks good to me. You probably jsut werent getting enough flow with the selenoid.

And that sprinkler valve is choking the flow quite a bit but it should hurt you too bad. C:B looks pretty good too.
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Unread postAuthor: jackssmirkingrevenge » Sun Oct 26, 2008 6:09 pm

x2percentmilk wrote:EDIT: when you say sharpen the barrel, do you mean file the outside down or file the inside down, or both?


Filing down the inside will give you a tighter fitting projectile meaning less air is wasted escaping around it, but advantages gained might be countered by increased friction. The reverse goes for sharpening the outside.
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Unread postAuthor: iisthemuffin » Sun Oct 26, 2008 6:38 pm

Most people file down the outside i think.

I did mine with a orbit sander. I just went around the pipe.
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