Full Auto Marble Gun

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
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mark.f
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Fri Oct 13, 2006 8:46 am

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This is my automatic marble gun.

I've had it built for a while now, I was just waiting on a camera.

The operating principle is simple: you connect an air compressor or other high-flow, high-pressure system to the gun with a female quick disconnect, and then open the ball valve. The source fills the chamber through the pilot, and when it hits 90 PSI, the pop-up valve triggers and pilots the 1/2" Q.E.V.

The feed system is a paddle-interrupter type. With each shot, the air-flow pushes up a paddle which interrupts the flow of marbles into the "chamber" and allows only one to fire. I also sleeved half a piece of 1/2" PVC into the tee for easier feeding of marbles into the barrel.

Here's some more pictures...
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feed.jpg
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Hope you like it!
Last edited by mark.f on Sun Oct 20, 2013 3:23 pm, edited 3 times in total.
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saladtossser
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Fri Oct 13, 2006 10:40 am

awesome, i would never be able to make that feed system
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mark.f
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Fri Oct 13, 2006 11:05 am

Bah... all you need is a hacksaw, a drill, a file, and some marine adhesive sealant!

(Oh, and some threaded rod and some neoprene)
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CS
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Fri Oct 13, 2006 11:36 am

Noice! [Got a lot of questions]

From the videos Id estimate that you were shooting around 240RPM. Would that 'guess' be fair to say?

Next, how big is your tank on the air compressor?

My mom is considering the purchase of a 20 or so gallon compressor, so im very intrested in this style of laucher. Also gonna need to find a lower pressure activating popoff because all of the ones ive seen locally activate at higher pressures of 125PSI. Also I wonder if you could use a sprinkler valve in such a design. Although there would be a larger venting area, that could be reduced by tapping both the ball valve inlet, and the popoff directly into the top of the sprinkler valve, and then removing the filter out of the equalization point in the diaphram. Anyway, as you can see, I like it a lot. Noice job!
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joannaardway
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Fri Oct 13, 2006 12:32 pm

I like this a lot!

If I were doing it myself, I can see some possible improvements to make to the feed mechanism, but I can't complain.

I like the pop-off valve trick, and although I'd prefer a slightly higher triggering pressure, I can't deny that it works.

But, don't get me wrong - I want one!
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Brian the brain
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Fri Oct 13, 2006 1:53 pm

Very nice!!!
I have been thinking of something like this to improve my MMG and make it more powerful...

First of all I can't find a qev,
second, I had no idea how to fit DR's paddle in a tiny T like that.
Third...I can''t get pop off valves either.

I got the idea from Salad's m16.Pretty amazed you pulled it off.To me it was one of those "in theory this could be done"kinda things.
Too bad I can't build one like this one.

The only thing I would like different if I could build one would be the ballvalve.It could be replaced by a blowgun, because flow doesn't affect fps, only rpm.It would look better and be better controlled.
I love this thing!!!
I wanna copy it so bad and run it on onboard CO2!!!
You built my dream MMG I think!!
Congrats!!
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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mark.f
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Fri Oct 13, 2006 6:12 pm

Noice! [Got a lot of questions]

From the videos Id estimate that you were shooting around 240RPM. Would that 'guess' be fair to say?

Next, how big is your tank on the air compressor?

My mom is considering the purchase of a 20 or so gallon compressor, so im very intrested in this style of laucher. Also gonna need to find a lower pressure activating popoff because all of the ones ive seen locally activate at higher pressures of 125PSI. Also I wonder if you could use a sprinkler valve in such a design. Although there would be a larger venting area, that could be reduced by tapping both the ball valve inlet, and the popoff directly into the top of the sprinkler valve, and then removing the filter out of the equalization point in the diaphram. Anyway, as you can see, I like it a lot. Noice job!
I didn't record the firing rate on this video, (I recorded 4.33 hertz on an initial test video on my cell phone), but if I take 4 hertz and convert to RPM, you get exactly 240 RPM.

The air compressor I'm using is a small little 100 PSI 2 gallon one. I'm actually seriously considering getting a higher pressure one with a larger tank volume, but I dunno if it's worth it. At my dad's house we've got a larger 33 gallon one that works at 155 PSI. I'm betting when I hook it up to that sucker regulated down to 100 PSI, I could empty clips all day long with little or no interruption.

The only pop-off valves I could find locally are the higher ones, (125, 150, etc...), so I ordered a 90 PSI model off McMaster along with the 1/2" Q.E.V.

It <I>might</I> work with a sprinkler. I have only owned one sprinkler valve in my lifetime, though, so I wouldn't really be the guy to ask. I <I>think</I> it might work well because you'll be filling from the chamber, (I guess), with the pop-off on the pilot. That way, you're 100% guaranteed the chamber is completely filled when the pilot hits your target pressure.
I like this a lot!

If I were doing it myself, I can see some possible improvements to make to the feed mechanism, but I can't complain.

I like the pop-off valve trick, and although I'd prefer a slightly higher triggering pressure, I can't deny that it works.

But, don't get me wrong - I want one!
Yeah, I though a little about the feed mechanism. I saw a few elaborate ideas, but eventually I chose the simplest because I didn't want this thing to break or anything gay like that. I'm actually considering increasing, (however slightly), the surface area of the paddle to help me to use larger magazines. I figured out today that when I used a larger mag, (like my 1/2 x 12" pipe nipple), the misfires at the beginning get more common, because the paddle doesn't have enough force inherent in it to push the marbles back up into the magazine. Increasing surface area may remedy this problem.

I also wanted this to be a "plug and play" cannon. 90 PSI was a good choice for me first of all because my compressor here can only go up to 100, (giving you 10 PSI buildup for shooting). I assumed all compressors could go AT LEAST to 100 PSI, so I chose 90.
Very nice!!!
I have been thinking of something like this to improve my MMG and make it more powerful...

First of all I can't find a qev,
second, I had no idea how to fit DR's paddle in a tiny T like that.
Third...I can''t get pop off valves either.

I got the idea from Salad's m16.Pretty amazed you pulled it off.To me it was one of those "in theory this could be done"kinda things.
Too bad I can't build one like this one.

The only thing I would like different if I could build one would be the ballvalve.It could be replaced by a blowgun, because flow doesn't affect fps, only rpm.It would look better and be better controlled.
I love this thing!!!
I wanna copy it so bad and run it on onboard CO2!!!
You built my dream MMG I think!!
Congrats!!
It WAS a little difficult to work with a design inside such a small tee. Eventually, though, patience and concentration got through, (it took a few tries and test fits), and I got the thing built.

The main reason I don't use blowguns is because they're not as cheap as ball valves. For some reason, they cost about 11 bucks where I live. How much do they run ya'll at across the pond?

I've also definitely got the money to get a small paintball CO<sub>2</sub> regulator, but not the means. It would also require buying another 20 ounce tank, (so I'm not using my actual paintball CO<sub>2</sub>), so the answer to that one is yes, I will definitely get CO<sub>2</sub> set up on it... just "eventualy".


Thanks for all of the positive comments you guys! I don't mind more questions, either, but still I don't see anything elusive in the posts.
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MrCrowley
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Fri Oct 13, 2006 6:17 pm

$11US for a 1/4" blow gun?
i get mine for $10NZD($6US) unless yours is a bigger size blow gun?
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mark.f
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Fri Oct 13, 2006 6:26 pm

Well, it depends. They have the cheapo ones you use for blasting sawdust off your table, and then you've got the cast steel ones like they sell on McMaster than you can use for pretty much anything, (they're also rated a little higher, IIRC).
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killagorrila99
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Fri Oct 13, 2006 10:33 pm

NICE! sweet looking gun you got there. Im in the process of rebuilding my mmg and makin' it amazing! ya no what would make it loverly? A bigger chamber.
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experament_u2
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Sat Oct 14, 2006 5:09 am

im not usally a dan of copper or metal guns but that is one of the madest mmg iv seen in a while very nice work
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mark.f
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Sat Oct 14, 2006 8:48 am

Here.
paddle.jpg
This mod adds more surface area, which should make misfires like the one in the video nonexistent.
Last edited by mark.f on Sun Oct 20, 2013 3:23 pm, edited 3 times in total.
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killagorrila99
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Sun Oct 15, 2006 12:02 am

Good job, Can someone give me a diagram on that feed system, Im very interested in this gun as I may be rebuilding me MMG soon...
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mark.f
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Sun Oct 15, 2006 12:06 am

It's just a paddle that swings up when you shoot to stop the flow of marbles.
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killagorrila99
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Sun Oct 15, 2006 12:15 am

OH i see! I actually get it now!
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