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Butt loading 63mm air cannon.

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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Butt loading 63mm air cannon.

Unread postAuthor: baldusi » Mon Mar 20, 2006 2:58 pm

I've made this cannon out of 63mm (2.25") 150psi PVC tubes. It fits a Nerf perfectly and I truely believe that is way overdimensioned. It's about 125cm (50") long and it's of a blowforward design. It's a stacked tube design ;). The lower tube consists of the main air chamber (the long part), he bolt part (the T), the spool chamber (the short part) and the spherical 3-way (not shown). The top tube is the breech and barrel.
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Here's the bolt. It's made out of PVC and it's hollow in the center with a one way valve. The smaller face seals the main air chamber while the big back seals the spool chamber. To load the air you simply connect the air through the 3way. That fills the spool chamber. This pushes the bolt forward sealing the main air chamber. The air flows through the bolt to the main chamber filling it. To shoot you just switch the 3way (manually) so you dump the spool. The maing air chamber pushes the bolt backwards liberating the air. It flows through the T to the breach which was sealled from behind with a drumstick.
This is a quick CAD I made. The Back o-rings are missing but you can see the grooves. And it lacks any sort of air color.
This is in the charged position. The black part is a rubber seal. The air in the T connector is at atmospheric pressure. On the right and left of the bolt is at 120psi. The air on the right has more area than the air on the left.
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This is the open position. You simply dump the air on the right and the pressure on the left will push the bolt back, liberating the air through the T connector. I'm missing a little plate a put on the left (tip) of the bolt in such a way that when there's pressure from the right, it will move and allow the air to pass freely. But when you depressurize the right side, it will get pushed against the front and seal enough to let the air push the bolt.
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We shoot this home made sabots. I don't know how do you call those foamy thingies. But are used by kids in swimming pools. When lathed to size they make excellent selas for the sabots. This sabot used a cut down cupboard. But later version only use cardboard.
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Since the bolt might stick, I've made the two tubes separated. The passage is sealed with an o-ring and both parts are joined with a tow line. Some experiments broke some 120lb plastic seal (somebody knows the translation for Spanish "precintos"?).
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The cannon is filled with a tire valve to 7bar (100psi).
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Then the sabot or nerf (we don't have them here) is introduced.
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The drumstick use is twofolt. First is used as a rod to push the sabot beyond the air connection (the T). Then is recessed to seal the back. In the picture the o-rings are placed in the wrong side. Sorry for that.
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At las a simple SS pin holds the drumstick in place.
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I've shot a 30 rounds sabot to 80m (~87yd). Beyond that, the spread is too much and the drum usually acts as an air brake at first. With 8.5 bars (125psi) I've chronoed it to 360fps.
Due its raw power it's used only for indirect fire. But I was wondering what you think about it and if it would make a good main cannon.
I'm adding a link to google videos I made as soon as those get verified.
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Unread postAuthor: dentlauncher » Mon Mar 20, 2006 3:33 pm

the foamy tthinga are called noodles
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Unread postAuthor: boilingleadbath » Mon Mar 20, 2006 4:58 pm

Nice cannon... well thought out and executed.
Problem with things like this is that they get almost no replys compared to a pill-bottle mini someone put together in 30 minutes. It's terribly frustrating.
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Unread postAuthor: drac » Mon Mar 20, 2006 5:39 pm

You have a lathe? Nice. You should look into making some piston valves.

That's a nicely built cannon, I like it. Sadly, what BLB said is quite true.
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Unread postAuthor: Shrimphead » Mon Mar 20, 2006 7:33 pm

I like the drumstick idea. It's very intuitive. Nice cannon, and I agree with drac, make a piston gun.
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Unread postAuthor: dragon finder » Mon Mar 20, 2006 9:13 pm

hey baldusi you could use my 2" sabot with that gun http://www.spudfiles.com/forums/viewtop ... ter=sabot&
just add a 1/4 inch to the mesurements and it should work great.

And that is a really cool gun and an inovative sabot. I am going to get a lathe soon.
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Unread postAuthor: boilingleadbath » Mon Mar 20, 2006 9:19 pm

"make a piston gun"
Uh... guys... this is a piston gun.
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Unread postAuthor: dragon finder » Mon Mar 20, 2006 9:24 pm

Hey I just rememberd a regulation pool ball will fit in that barrel because regulation pool balls are 2 1/4" in diameter.
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Unread postAuthor: drac » Mon Mar 20, 2006 9:25 pm

Ohhhhh. Now that I review that diagram, I see that it is. That's quite a unique design. I'm sitting here beating myself up for not noticing.
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Unread postAuthor: dragon finder » Mon Mar 20, 2006 9:41 pm

:lol: :lol: :lol: BRAIN FART :lol: :lol: :lol:
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Unread postAuthor: Shrimphead » Mon Mar 20, 2006 10:29 pm

Yep, sorry about that. Must not have been thinking (not that it's unusual for me) :)
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Unread postAuthor: CS » Tue Mar 21, 2006 3:47 am

Very nice clean construction. I like the idea on the loader, just not that it requires orings.

I think why these style of launchers dont get replys is because theres nothing to really comment on besides, "nice job!".
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