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True Semi

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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True Semi

Unread postAuthor: PCGUY » Sat Feb 05, 2005 6:28 pm

<div align="center">TRUE SEMI

Provided By Mr.Plow - <a href="http://www.geocities.com/boomstick989">http://www.geocities.com/boomstick989</a>

T he first development of my semi-auto idea was completed weeks ago. It consisted of a tri-chambered design with three independently operated blowgun-modded sprinkler valves linked to a 1" diameter barrel by means of a 1" cross. A tee and small section of pipe just before the barrel acted as the hopper, with a 15 round capacity. Although a complex system of smaller electronically actuated valves connected to a timer relay circuit was devised to make the gun essentially fire full automatic, it never got past the initial phases using 3 plain ol' blowguns. Ammunition was at first a limited number of round wooden balls I found in my basement that loosely fitted the barrel. While the initial design worked, it was extremely unreliable. One test would work perfectly, shooting all 15 balls without jams or other problems, and right after that the next test would go FUBAR in every possible manner! Obviously, it was flawed in several ways. I scrapped the tri-chambered design, for now focusing on resolving the problems encountered with just one chamber. Perhaps sometime soon I'll rebuild the original with all the bugs worked out...

Working out the magazine jamming issues was easy; a little dremeling the inside of the barrel plus plastic balls for ammo that actually fit the barrel did the trick. The most difficult problem was getting the valve to re-seat the diaphragm quickly enough. Since air was continually flowing into the chamber, the valves had the tendency to "honk" after each shot for 4-10 seconds as the diaphragm vibrated quickly. To fix this problem, I removed the inner spring and essentially made a bigger equalization port by adding an air-in line to the top of the valve. Of course, I had to limit the amount of air going to the top of the diaphragm (or else it wouldn't fire), so I added the needle valve with gauge. With the chamber at 40psi and the top restricted to a little less than 10psi, it works like a dream! I can get about 3 shots per 2 seconds, and I estimate the ammo is getting more that 150fps (although I dont have a chrony...so a real number will have to wait)

Provided By Mr.Plow - <a href="http://www.geocities.com/boomstick989">http://www.geocities.com/boomstick989</a></div>
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Attachments
autoammo.jpg
Heres an example of one of the plastic balls that I shoot.
autoammo.jpg (16.93 KiB) Viewed 5854 times
Auto_valve.jpg
Closeup of the valve assembly. If you notice, only two screws are in the top of the valve (I forgot to replace them before taking this pic...I was previously showing off the internals of the valve to a friend)
Auto_side.jpg
Here's a side view of the cannon. In case you're wondering, the black tape is cosmetic, hiding the blue cement I used...no, its not taped together!! ;)
Also, as you can see, the air system plugs into a compressor with an industrial plug. The regulator you see is a detroit pneumatics mini-reg I got for free. I love the look of those braided steel lines (also free!)
Last edited by PCGUY on Tue May 02, 2006 11:02 am, edited 1 time in total.
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Unread postAuthor: theexp » Sun Feb 06, 2005 4:43 pm

nice, i hope you get the jamming done, but i like it.
Real cool.
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Unread postAuthor: fred_roux » Mon Mar 28, 2005 9:55 pm

coooool...a simple way to get a semi-auto canon...thats really cool!!!!!....u shoult change the barrel for a golf ball barrell :twisted:
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Unread postAuthor: julz » Fri May 06, 2005 1:35 am

Darn... I just had his idea the other day and thought I was the first one :( . Good work though. I reckon i will make soon a 3-5 chambered, single barreled cannon. The only thing i can find that wold be dodgey would be the size of the chamberes, as the gun needs to be portable. I hope to have this built within the next... :roll: year. :) It will take a while and must be a secret bye!
---Julz
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Unread postAuthor: spudshot » Fri May 06, 2005 3:26 am

as far as arranging the chambers to be portable julz, you could just use elbows to make the chambers go the same way as the barrel, so all you have is a cannon slightly longer than the barrel
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Unread postAuthor: deathtodeer666 » Tue Sep 06, 2005 1:29 am

aaah! how do you make the sprinkler valve work with the blowgun, I can under stand if it just releasis presure.
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Unread postAuthor: spudshot » Tue Sep 06, 2005 5:30 am

there is pressurized air on both sides of the diaphragm, using the blowgun you exhaust the air on top of the phragm, so there is no pressure above, and your chamber volume is still pushing from below, that pushes the phragm up and allows the air go to to the barrel
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Unread postAuthor: saladtossser » Tue Sep 06, 2005 2:19 pm

i honestly dont know how this gun loads. and i dont get y there are 2 hoses coming from the valve, those clear hoses dont take a lot of pressure.
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Unread postAuthor: sgort87 » Sun Sep 18, 2005 10:58 am

Neat! But you need to elaborate on your system there. The valves and loading.
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Unread postAuthor: Andrew52 » Tue Mar 28, 2006 11:21 pm

yes but its still an awesome gun
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Unread postAuthor: spud yeti » Tue May 15, 2007 4:39 am

How does it load for semi auto??
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Unread postAuthor: chaos » Tue May 15, 2007 4:51 am

Oh No's



check the dates before posting pwease.
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Unread postAuthor: cb4289 » Wed May 16, 2007 1:48 am

spudshot wrote:there is pressurized air on both sides of the diaphragm, using the blowgun you exhaust the air on top of the phragm, so there is no pressure above, and your chamber volume is still pushing from below, that pushes the phragm up and allows the air go to to the barrel



so on those air nozzle triggers that bcarms.com sell's when you pull the trigger dose air come out the bottem or not :?:
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Unread postAuthor: A-98 » Wed May 16, 2007 2:27 am

*sigh*

look, heres a link to all of your needs. CLICKY! and if not that then this
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Unread postAuthor: cb4289 » Wed May 16, 2007 2:33 am

oh now i know what a modded sprinkler valve is and how it works... cool
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