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Semi-auto coaxial

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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will thsi work

yes
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no
3
43%
 
Total votes : 7
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Semi-auto coaxial

Unread postAuthor: hi » Tue Mar 20, 2007 6:04 pm

I already posted this on spudtech And now I'm posting it here.

http://img362.imageshack.us/img362/2290/project1zk5.png

Will this work? I call it the "hi loader". The idea is that a paint ball or a marble drops in the barrel and chambers as you are refilling. There would be two ball valves, one for filling and one for firing. Im guessing I could take about 1 shot per second with practice. I will be building this within the next two weeks, so if you dont think it will work let me know

PS- the pink thing in the middel is a tee. One thing a member on spudtech pointed out is that a ton of air would go up the tee. I thought that puting a ball valve there and opening it when i wanted to reload.
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Unread postAuthor: FeLeX » Tue Mar 20, 2007 6:14 pm

I dont get how this is supposed to make it semi auto... are you going to connect it to air compressor and put marbles into the pink tee if yes then thats actually pretty smart because thats like breach laoded coaxial.
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Unread postAuthor: hi » Tue Mar 20, 2007 6:22 pm

Yes, thats exactly how it works.
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Unread postAuthor: Hawkeye » Tue Mar 20, 2007 7:00 pm

I drew up the exact same plan using copper fittings. The small T would have to be shortened on the loading side so it would fit into the larger T.
I use copper glue which sets very quickly and i couldn't trust the chance of trying to slide the magazine tube through one fitting and all the way into the interior T while keeping it all accurately lined up.
I might get around to trying it using a slow setting Epoxy.
The problem would be the difficulty in making sure the passages are all clean of excess glue that may interfere with the travel of the ammo.
There was a thread over at Spudtech showing a similar design which was mainly trying to eliminate dead space.
PS It was a different set of diagrams on Spudtech.
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Last edited by Hawkeye on Tue Mar 20, 2007 7:02 pm, edited 1 time in total.

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Unread postAuthor: keep_it_real » Tue Mar 20, 2007 7:00 pm

ohh I just thought of a good idea. You could drill a hole on the outside of the firing ball valve and then drill another small hole on the actual ball part that is perpendicular to the main hole. This makes it so when you want to fill the chamber, just open the ball valve and when you want to shoot it, close the valve and the air goes through small hole and out the side of the ball valve. This basically does the same thing as a qev or a slide valve so you could just buy one of those but this would be cheaper. I seriously doubt if you can understand my French so I'll draw a diagram if you need some more help.
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Unread postAuthor: hi » Tue Mar 20, 2007 7:14 pm

Ya i get what you are saying keep it real. That would work, but I wouldnt trust it. I Think I am going to just moddify my current coaxial.

hawkeye- Thats why you do it before you glue the tee on. You dont need to shorten anything, you just need to use some pipe. And if its copper why dont you just use solder? It may be a little messy, but at least you could re-do it if you had to.
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Unread postAuthor: to_live » Tue Mar 20, 2007 7:23 pm

i dont get the drawing it looks like a 4 year old drew it? redraw it better
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Unread postAuthor: keep_it_real » Tue Mar 20, 2007 7:33 pm

It doesn't really need to be drawn. It's a barrel sealing coaxial meaning that the piston moves backward to let the air through the barrel. It's loaded by dropping a paintball down the tube into the barrel.

hi: I think you should try making a blow forward bolt. I made one here:
http://www.spudfiles.com/forums/viewtopic.php?t=6343&
I did it without a lathe so it was pretty easy. The only problem was it chopped paintballs but you won't have that problem if your dropping them in one by one but it will just stop the air flow from the T fitting. Maybe if you make it the right size you can just use a clip. That would be sweet.
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Unread postAuthor: zeigs spud » Tue Mar 20, 2007 7:49 pm

it should work i don't know why not.
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Unread postAuthor: deusXmachina » Tue Mar 20, 2007 8:16 pm

Why do you have to put the tee in the middle of the valve? You can just as easily achieve the same effect if you put the tee out in front. If you're concerned about pressure leaks you can use a bolt-action. And with all that extra space in the valve, you could easily make a typical piston valve.
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"On a scale from 1-10, I hope you fall in front of a bus."

:white stuff pours out of piston: "What is that? It looks like milk."
"....<i>Well...</i> it's not milk."

YAAAAAAAAYYYY WE'RE DOOMED!
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Unread postAuthor: hi » Tue Mar 20, 2007 8:30 pm

Yes, i know its a crappy drawing. And no, you dont need the tee in the middle, it would actually be closer to the piston, it just drew it so you would know how it works. I am not worryed about pressure leaks, If i glue it properly it will hold just fine.

to_live- Im not drawing another one, if you cant figure it out then that sucks for you. If you really want to know, search the forms and learn about piston valves. In short, it works on pressure differences.

By the way, is a union completly air tight? i was thinking i could have the chamber screw apart incase there is a problem.
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Unread postAuthor: deusXmachina » Tue Mar 20, 2007 8:41 pm

Yes, unions are airtight, otherwise many houses would have some issues with raw sewage :( .

And I highly reccomend using modular components because these sort of valves tend to be very finicky, especially if you're trying something new, and I know firsthand how much it sucks to have something not work quite right, and you have a solid chunk of solvent-welded PVC in front of you.

I would go with the union and also thread the connection between the Tee and the reducing coupler that attached to the barrel that runs through it (purple on your diagram) so you can pull that entire assembly out to work on the sealing surface.
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"On a scale from 1-10, I hope you fall in front of a bus."

:white stuff pours out of piston: "What is that? It looks like milk."
"....<i>Well...</i> it's not milk."

YAAAAAAAAYYYY WE'RE DOOMED!
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Unread postAuthor: ShowNoMercy » Tue Mar 20, 2007 8:47 pm

Could you possibly use a few o-rings in the 1.5 " tee where the back half of the gun attaches and then use some set screws instead of glueing that part in? Or would that be too much pressure for it to handle? That way you could easily separate the gun to access parts and it provides no restriction to flow.
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Unread postAuthor: MrCrowley » Tue Mar 20, 2007 10:37 pm

Bushing not 'Brushing'.

I just saved you for the next time you go to the hardware store and ask for a brushing. :P
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Unread postAuthor: hi » Tue Mar 20, 2007 11:50 pm

lol, thank you MrCrowley. I guess you do learn something new every day.
The people at my hardware store are stumped when i ask for an end cap, so it dosnt really matter, but i guess it does here. 8)

Show no mercy, O rings that size are kinda hard to find, i think ill stick with the union, but if you or any one else has any suggestions I would appreciate it.
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