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3" Barrel Inline 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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3" Barrel Inline Pneumatic

Unread postAuthor: tmacd995 » Thu Feb 28, 2008 10:43 pm

This is my second launcher, my first was a simple over/under with a ball valve. This one has 4'x4" chamber with a schrader in the cap. I am shooting duct taped tennis balls with it for the first time this Saturday. Later I'll probably mod the 1" valve so that it dumps air faster. The sweatpants are covering up jeans that are wrapped around the chamber just to make me feel safer. The leads from the solenoid are 35' and go into a project box with a safety and momentary switch.
-Thomas
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Attachments
IMG_1376.jpg
View of the entire thing, its mounted to the plywood to make it semi portable and not stress the joints
IMG_1377.jpg
The control box with the 2 switches
IMG_1389.jpg
The solenoid and the ammo

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Unread postAuthor: bigbob12345 » Thu Feb 28, 2008 11:23 pm

Nice job for a second.
But that 1in sprinkler is really constricting flow even if you modded it I would reccomend a 2in sprinkler or if you dont want to spend 90bucks on one a triggered burst disk setup(check wiki). A piston valve would be ideal but I am doubting that you are experienced enough to make one.
and why is the gun wrapped in a bunch of stuff it has been proven it wont help in the event of an explosion it just makes it worse.
and the coupling in the first pic is DWV the bushing doesnt extend all the way into it.Replace that and if there are any bell reducers on it replace those as well.
Other than all that nice gun do you mind if i ask what you pressureize it to.
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Unread postAuthor: Hubb » Fri Feb 29, 2008 1:39 am

Wow. You not worried about this thing blowing up, are you?

The wrapped tennis balls look like miniature cannon balls.

You said that you wanted to mod the valve, but you also said that you have 35' of lead wire coming from the current setup. Does this mean you plan on making a pilot for the valve 35' long as well? I hope not.

Here is a way you can mod the valve and still keep the 35' of wire:
1) purchase another sprinkler valve
2) mod the current setup and adapt a 1" thread
3) place the second sprinkler valve onto the 1" thread
4) hook the leads to the new solenoid

That should provide you with adequate opening time, as well as the safety you so desire.
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Unread postAuthor: tmacd995 » Fri Feb 29, 2008 7:38 am

1)Thanks for spotting that DWV and letting me know
2)I have so far pressure tested it to 60 PSI
3)I didn't know that stuff wouldn't help if it blew up, another site had suggested it, I'll take it off
4)Yes after reading that PVC didn't show up on X-Rays, I am a little nervous it might blow up
5)Thanks for the tip on modding that valve, I think I might try a burst disk setup
-Thomas
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Unread postAuthor: bigbob12345 » Fri Feb 29, 2008 9:05 am

What was this other site that suggested you cover it with stuff?
Check every joint that is on there and make sure it says nsf-pw if it says nsf-dwv you will have to remove it.
this has potencial to be a great and powerful cannon .
And with the burst disk thing I reccomend you go with a 2in union but you go through a lot of foil with those I guess a 1.5in union wouldnt hurt performance *that* much.
And are you planning a triggered burst disk setup or just pressurizing it until it blows
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Unread postAuthor: Pilgrimman » Fri Feb 29, 2008 10:04 am

Glad to see a new member concerned with safety! Nice cannon, but you would see a MASSIVE performance increase if you used a 2" sprinkler valve or just a piston valve. However, it seems to get the job done the way it is!
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Unread postAuthor: tmacd995 » Fri Feb 29, 2008 11:10 am

Alright I have a thought here... (but feel free to shoot me down)

1)All the fittings on the chamber are DWV until the 2" pipe and then there is that one DWV on the barrel.

2) Looking at 4" SCH 40 fittings they are incredibly expensive.

3)I have alot of 2" SCH 40 pipe laying around my garage

So...
Would it significantly affect performance to substitute 2" PVC pipe for a chamber?

I am thinking that the equation for volume of a cylinder is V=(pi)(Radius Squared)×height
so...
16 feet of 2" pipe would have the same volume of air in the chamber as the current 4'x4".
I have easy access to 2" pressure rated fittings, but not 4" fittings and a couple tees and caps could keep the 2" pipe in a similar footprint.

Thanks for your help...
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Unread postAuthor: Jared Haehnel » Fri Feb 29, 2008 11:20 am

Nice gun..funny story I wrapped my first combustion with old jeans and duct tape for fear of explosion...

Once you get those dwv joints replaced there should be no fear of explosion within reasonable pressures.
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