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First pneumatic.

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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First pneumatic.

Unread postAuthor: Slyder2k8 » Tue May 03, 2011 10:36 pm

I know to alot of ppl that have been at this for a while this will seem a lil chincy. The plans were printed in 2002. Needless to say they were a bit out of date. Any how here are the specs. All pipe and fittings are sch40 pvc.

1.Air chamber=2x24" with a 125psi gauge-"bolt" in tire valve.
2.Body and stock=3/4 pipe and fittings
3.Valve=Rainbird cp100 1" inline valve.
4.1"x40" Barrel-The barrel was beveled at one end to "seat" better in the rubber bushing. A 1.5" outer barrel was capped with 1.5" to 1" bushings. The front bushing had to have the inner lip shaved off to allow the 1" barrel to slip threw. I need to add supports for the barrel as it is "bouncy" if not held in place while shooting. I was thinking of "cupping" the ends of some 1" pipe and gluing it in place rather than the traditional wood and band clamp. Any advice on this would be welcome.

I have added a pic and hopefully will get some damage footage soon. Any criticism and advice is welcome. Like i said I'm new to the pneumatic guns so hopefully it doesn't look to bad.

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Unread postAuthor: whoa044 » Tue May 03, 2011 11:06 pm

I would recommend modifying that sprinkler valve. You'd shed some weight, and make things a little simpler.

edit: How to modify a sprinkler valve
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Unread postAuthor: Slyder2k8 » Tue May 03, 2011 11:09 pm

LoL yeah i didnt realize you could mod these till after i had already wired the project box and cut the piping for the spacing. I figured i would use this one as is. And do the mod on the next one. (soon to come). I have bookmarked several vids on youtube on how to mod them and read tons in the last couple of days here. Other than the sprinkler valve does it seem to be a decent "gun"?
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Unread postAuthor: whoa044 » Tue May 03, 2011 11:29 pm

Yeah I would say it is a fairly nice looking gun.
Does air pass through the T fittings right before the valve and the one nearest to the chamber?

If you were weary on having a shorter barrel, don't be. It seems like with the distance the air has to travel from the chamber to the barrel, a longer barrel would be good.
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Last edited by whoa044 on Tue May 03, 2011 11:44 pm, edited 1 time in total.

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Unread postAuthor: jackssmirkingrevenge » Tue May 03, 2011 11:43 pm

Well made for a first project, though as you said it needs some support between the barrel and chamber. Do mod the sprinkler valve, you will be pleased with the performance increase ;)
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Unread postAuthor: Technician1002 » Wed May 04, 2011 12:22 am

My only suggestion would have been to make the stock out of beefier pipe (2 inch) and use it for the chamber instead of having a dangling chamber on a small pipe. The small pipe is a weak spot with lots of leverage on it. If the stock was made with larger pipe and used as a chamber, the flow and strength would be improved.
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Unread postAuthor: Slyder2k8 » Wed May 04, 2011 1:07 am

The air itself is passed threw the entire stock assembly. But i figured with the barrel being positioned so close to the valve it would be ok. i Get 3 good shots with it at 100psi. Im hoping the addition of the supports will increase the strength and stability of the barrel. Got to looking at it and decided to go with movable supports so i can change out the barrel. for golf-balls, larger projectiles, and a t-shirt launcher. :) thought it would come in handy at the fireworks stand.
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Unread postAuthor: Slyder2k8 » Wed May 04, 2011 9:06 pm

Modded the valve today. The pressure drops all the way to 0 from 60 in one burst lol. And i still get the wicked "HONK" threw the valve. I read the q&a on that and it said adding this mod would fix that. Sadly it did not for me. And ideas on what else i could do? Oh i also did the spray with the white lithium grease. Heres a pic of the valve after the mod. Im sure you guys have seen tons i just wanted to let you see if there was anything i did wrong. Maybe is why the Honk didnt go away. The epoxy is called "Sonic weld" it is a steel reinforced putty. So its a little easier to work with than jb weld. I forgot the temp rating on it but its rated to 3500 psi. So it should never budge.

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Unread postAuthor: potatoflinger » Wed May 04, 2011 10:09 pm

If the valve is honking, you may want to shorten the length of hose you have between the sprinkler valve and your pilot valve. Too much pilot volume and a low flow pilot valve can lead to honking issues.
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Unread postAuthor: Technician1002 » Thu May 05, 2011 12:51 am

Another source of the honk is a flow restriction between the chamber and the valve.

The honk is caused by the valve opening, the pressure into the valve very quickly falling off due to the flow restriction which closes the valve again because the pressure into the valve dropped faster than the pilot pressure dropped. When closed, the pressure from the chamber equalizes raising the pressure into the valve as the pilot pressure continues to drop where the process repeats.

Either or both of too small a pilot and flow restriction into the valve will cause honking. Both must be fixed to stop the honk.
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Unread postAuthor: Slyder2k8 » Thu May 05, 2011 1:02 am

I will try modifying the blowgun. i read the section for modding the piston and the diameter or the holes in the "pass threw". The flex tube i have on there now is rated for 160psi does it need to be this high. The only other one they had was only rated at 50psi. Would this be ok? it is much more flexible and easier to work with.
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Unread postAuthor: Slyder2k8 » Sun May 08, 2011 6:35 pm

Update. All but eliminated the "honking" with the mods to the blow gun. Found some 3/8th steel braided flex line. Going to replace the plastic one with this. Looks better and has same pressure rating. will post pics and damage vid after the paint job. Flat black of coarse :)
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