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Worklog: Schis's 4" Coaxial (update 3)

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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Worklog: Schis's 4" Coaxial (update 3)

Unread postAuthor: schismatized » Mon Jul 02, 2007 4:08 pm

4" Monster Coaxial (working title)

Alright so I am in the process of building a fairly large coaxial, for under $100. It will be my first attempt at a gun this size or a piston valve. The cannon is going to be meant for distance. I'm aiming for at least 1000 feet with just about anything stuffed in the barrel, and hopefully 2000 feet with some finely tuned projectiles.

Scale Design (v2):
Image
Image
This design is far superior to the first one. First of all, I added a ball valve in front of the quick disconnect, to allow for quick shutoff from the compressor. I also added a quick release safety valve, and removed the 4" adapters. This is where it gets interesting: As you can see, the whole rear coupler removes easily by the way of 4 draw latches. The middle couple is there to make a thicker mounting area, so that i can install the catch on the pvc. (i need to find some of these latches, anyone know where?) This will make loading much better. Also i have added a bumper, which will be attached to the removing assembly. It will be constructed from a big block of gum rubber. Oh yeah and i am going to fill the cap with foam to reduce the pilot volume.

Scale Design (v1):
Image

Specs:
10' x 4" Chamber
10' x 2" Barrel
3" Cap Piston
1" Sprinkler valve actuation

Parts (v2):
1- 10' x 4" Sch 40 PVC Pipe- FREE (Thanks Ewings)
1- 10' x 2" Sch 40 PVC Pipe-
3- 4" Sch 40 PVC Slip Coupler-
3- 4" x 2" Sch 40 PVC Spigot x Slip Bushing-
1- 3" Sch 40 PVC Slip Cap-
1- 2" x 1" Sch 40 PVC Spigot x Slip Bushing-
1- 1" Sch 40 PVC Slip x Male Adapter-
2- 1" x 1/2" Sch 40 PVC Spigot x Thread Bushing-
1- 1" Sch 40 PVC Cross-
_____________________________________________________________

I am getting most of my supplies from Ewings Irrigation:
ImageImageImageImage
ImageImageImage

_____________________________________________________________

Check back here often, I will update this frequently. I am open to any suggestions that anybody has to give.
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Last edited by schismatized on Fri Jul 20, 2007 4:03 pm, edited 5 times in total.
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Unread postAuthor: noname » Mon Jul 02, 2007 4:29 pm

Lower pilot volume as much as possible. In the back bushing, have the 1" pipe just long enough so that a 1" male adapter can be cemented on the end.
For really long distances, shoot those Nerf Mini Vortex footballs. They will extremely well in 2" Sch 40 and go a really long way out there.
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Unread postAuthor: origin unknown » Mon Jul 02, 2007 4:32 pm

First off, a projectile will keep accelerating faster if it is still being pushed by expanding air in the barrel. It stops getting faster and starts to slow down when it exits the barrel. A longer barrel with the right sized chamber will make your projectile go as far as you wanted it to go. I suggest you make the chamber extend almost all the way up to the tip of your barrel and make the whole cannon itself as long as you can make it for best performance. If you can, try to find one of those flat endcaps for your piston, I have heard they work better than the normal ones.
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Unread postAuthor: VH_man » Mon Jul 02, 2007 4:42 pm

Origin Unknown-

i dont know if GGDT is pulling my leg, but ive found that a coaxial cannon at 125 PSI with:

14" of 1 inch PVC as the chamber
48" of 1/2 inch copper as the barrel

i can get 550 FPS with a marble. the barrel pressure by the time the marble exits the barrel is around 45 PSI. if I make the chamber 48" long, i only get a 100 FPS increase. sure, its amountable, but still, its not like its gonna kill his cannons preformance. hehe. wait untill you guys see my Barret 14mm Remake. just wait. muahahahaha. the barrel/chamber above are main parts. but there is ALOT more. hehe. he. hehehehehahahahahahahaMUAHAHAHA

sorry.
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Unread postAuthor: schismatized » Mon Jul 02, 2007 7:11 pm

is there anyway i could get rid of the cross and still have my pressure release valve and gauge and stuff? this would also reduce the pilot volume.
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Unread postAuthor: wannabie » Mon Jul 02, 2007 7:20 pm

well i know that you could tap your fill valve into your sprinkler but im not sure about the release valve.
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Unread postAuthor: jrrdw » Mon Jul 02, 2007 7:37 pm

You can mount your gauge just about anywhere in a coaxle design. The shrader valve/fill valve should be mounted in the pilot chamber, inbetween the vent valve/sprinkler valve and the piston.
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Unread postAuthor: schismatized » Mon Jul 02, 2007 8:01 pm

I think i am just going to use a quick disconnect with a ball valve between it and the chamber. That should allow it to fill faster and i wouldnt have to stand there and wait while it fills, the compressor would just shut off. also, if i tapped the safety release valve, where do you think would be the best place? through the coupler and pipe close to the barrel opening?
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Unread postAuthor: jrrdw » Mon Jul 02, 2007 9:02 pm

You will still have to remove the air hose everytime you want to shoot, if you place the triggering valve, (ball valve), inbetween the chamber and fill. You should probly put the safty valve where ever the pipe is thickes, so in through the coupler and pipe sounds like a safe bet.
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Unread postAuthor: schismatized » Mon Jul 02, 2007 9:10 pm

shouldnt i be able to close the ball valve (closing off the connection to the compressor) and fire, without disconnecting the hose? then i would just open the ball valve to fill again.

EDIT: Also, since the cap fits pretty good in the 4" will there be a pressure spike in the pilot area when i fill the cannon? like will the pilot area jump up to 120 really fast while the chamber is only slowly pressurizing. I ask this because im thinking i should put the safety valve in the pilot area.
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Last edited by schismatized on Mon Jul 02, 2007 9:13 pm, edited 1 time in total.
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Unread postAuthor: turbohacker » Mon Jul 02, 2007 9:12 pm

Keep stuff off the side of the gun, were it is exposed to breakage.

My gun tottaly destroyed itself this weekend ( it was very much like this one exept only 6' long) I had a very cheap brass male quick connect and at 130psi it split right in half, causing my female quick connect to break off of the gun. This caused the gun to shoot out of my hands and land on my exposed spinkler valve and break it off. When the gun fired out of my hands it knocked over my 20lb CO2 tank and broke off a gauge from the regulator. Nevertheless, I did not shoot any more spuds that weekend, i went and sobbed at my loss :cry: :lol:
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Unread postAuthor: schismatized » Mon Jul 02, 2007 11:24 pm

good idea hacker, ill stay away from things poking out of the gun. sry for your loss :( . Also i have a quick question: I know for maximum performance this valve is supposed to open 1/2" to 1" but if it opened say, 1.5 inches, would it decrease my performance?
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Unread postAuthor: rednecktatertosser » Mon Jul 02, 2007 11:29 pm

I dont think it would but the farther the piston opens the faster it gets going before it is suddenly stopped by the end of the gun, therefore the greater chance of something shattering upon impact. If you do mak absolutely sure you have a very good bumper.
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Unread postAuthor: schismatized » Tue Jul 03, 2007 12:22 am

yeah i think i found a decent bumper: gum rubber. like the eraser kind or the kind on the bottom of your shoes. i have a big block of it that i am going to cut down. also, i think i may have found a way to make my own cam lock fitting, getting rid of the 4" threaded adapters and making for quicker reload times.
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Unread postAuthor: spud yeti » Tue Jul 03, 2007 7:25 am

Imagine the recoil on this baby! LOL, but good luck on building it, it looks like it should be great!
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