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Making my first Spud Gun

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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Making my first Spud Gun

Unread postAuthor: hatssold » Fri Apr 10, 2009 11:24 am

Hi guys, i recently became interested in pneumatic cannons and I am in the process of building my first one. To start off, I'm gonna build a basic over- under modified sprinkler pneumatic cannon. 2"x2' air chamber, and a 1"x3' barrel.

I've been doing research and I believe I'm almost ready to build one but I need some input on air intake sections such as the schrader valve. I plan on putting it on the end cap but I don't know a good way to put the valve in and which kind to use. Should I use a brass mechanical tire valve or will a normal bike valve do? Should i create a hole smaller than the diameter of the valve and just jam the thing in there?

Also I am looking for a good pump to use. Do you guys recommend a high psi shock pump?
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Unread postAuthor: mark.f » Fri Apr 10, 2009 11:41 am

I usually use the tire valves from Wal-Mart... the rubber ones. The come in short and long stem versions, and are usually no more than a few bucks for a little pack of two or so.

I usually just drill a 7/16" hole (make sure you take your time and get the walls SMOOTH, so you don't have any leaks), grab some pliers, and pull the stem through from the inside of the launcher (this obviously has to be done during construction). Also, make sure this is through a double layer of pipe (pipe/coupling overlap, etc.)

You should get a fairly good pop as the bead sets in place. If in doubt, keep pulling, as it takes a lot of force to seat the valve in place.

I recommend a cheap Husky floor pump like they sell at Home Depot. I've taken them to 300 PSIG before. Just make sure not to pump to fast or it'll overheat and fuse closed the check valve in it.

If you're looking for some examples of an over-and-under gun, DR made a good one a while ago, except it uses a 1-1/2" barrel. I think these guns look absolutely magnificent if done neatly and clean.

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Unread postAuthor: hatssold » Fri Apr 10, 2009 11:54 am

Hey thanks for the advice I appreciate it. I think i might have problem about the double layer whenever putting on valve. Since I have to pull the valve out from the inside, how do I get my valve in the hole in the first place? My arm is way too massive to fit inside the 2" piping. Maybe I should try a 3" air chamber instead?
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Unread postAuthor: mark.f » Fri Apr 10, 2009 12:04 pm

Well, I usually put my schrader and pressure gauge in the coupling closest to the valve before I glue in the last bushing. But, if you want it further back, you could use something like a piece of string or wire to pull the valve up to the hole, and then grip it with the pliers.

I think you'd need a 4" air chamber if you wanted to fit anything above your forearm into it. :roll: I'm only 130 lbs. and I can't even get my entire forearm into 3" SCH-40.
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Unread postAuthor: LCTChamp » Fri Apr 10, 2009 12:08 pm

It isn't absolutely necessary to put it through a double layer, it just makes it safer. If you put it through a single layer just make sure it isn't pointing at you. You could just get a shrader valve that threads in. You can usually get them at Lowes.
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Unread postAuthor: mark.f » Fri Apr 10, 2009 12:18 pm

lctchamp wrote:It isn't absolutely necessary to put it through a double layer, it just makes it safer. If you put it through a single layer just make sure it isn't pointing at you. You could just get a shrader valve that threads in. You can usually get them at Lowes.


That really depends on what Lowes you go to. I've personally never seen a threaded schrader valve at any local store around me. I've checked at Ace hardware, Lowes, Home Depot, my local hardware stores... I've looked around the compressors, the plumbing department, around the pumps, around the captive-air water tanks... everywhere, and I've never seen one.

Now, they do sell the metal bolt-in ones at automotive stores. Those do look a little neater, but require almost the same installation process, and don't work any different.

Also, putting it through a double layer of pipe is definitely recommended. If there's a chance it'll pop out (through not likely), why would you want to risk having to re-do the entire chamber just to replace the valve?
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Unread postAuthor: Technician1002 » Fri Apr 10, 2009 12:28 pm

lctchamp wrote:It isn't absolutely necessary to put it through a double layer, it just makes it safer. If you put it through a single layer just make sure it isn't pointing at you. You could just get a shrader valve that threads in. You can usually get them at Lowes.


I found my local True Value hardware store has them in the air tool accessories section right next to the gauges, manifolds, regulators and quick couplings.

In a pinch you can make one with a tire valve and 1/4 inch pipe cap.
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Unread postAuthor: mark.f » Fri Apr 10, 2009 12:33 pm

Well damn. I must just live in the middle of nowhe-- wait...
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Unread postAuthor: maverik94 » Fri Apr 10, 2009 4:58 pm

I would suggest, for the input valve, a schrader valve that can be screwed in, it has a nut and a thick o-ring for the inside, so this would be really easy to install, heres a pic:.....ok, I cant find one, But just ask at your local auto parts place for a schrader valve that screws into the tank and has a nut and washer, he/she'll know what youre talking about.
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Unread postAuthor: Hubb » Fri Apr 10, 2009 5:08 pm

Threaded schrader valves are not going to be found near the pop in schrader valves. They are used in air compressors, so that is the section they can be found.

Or, you could buy one from Gort
http://www.launchpotatoes.com/index.php?act=viewProd&productId=46
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Unread postAuthor: maverik94 » Fri Apr 10, 2009 10:07 pm

uhhhhhhhhhhhhhhhh, I have found these threaded schrader valves at both koi (its local) and NAPA auto parts stores. However, I guess you can probobly get one in the compressor section too, it depends where you're looking
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Unread postAuthor: hatssold » Sat Apr 11, 2009 1:11 am

Thanks guys 8) . Anyways, what kind of bike pump should i use? I dont really want to invest in a compressor right now.
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Unread postAuthor: jook13 » Sat Apr 11, 2009 1:36 am

I got a cheapo from k mart and it broke within a few days. I went to walmart and got a schwinn for like 12 bucks and it has lasted over 2 years of me pumping with all my weight (about 180 pounds) till it maxed out. I like my schwinn.
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Unread postAuthor: maverik94 » Sat Apr 11, 2009 8:37 am

I have had a hella foot pump for over 3 years, and it's just now begining to act up.
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Unread postAuthor: covey12 » Sat Apr 11, 2009 11:34 am

just go to ace hardware, the sell threaded schrader valves, all you do is drill a 1/2 inch hole, or 1/4 inch depending on which size you got, and screw the valve in there, works perfectly with no leaks at all, i suggest though putting it where the endcap is joined to the chamber, that way there is more pvc for it to hold on to because its twice as thick
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