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Nice find, and barrel length question.

A place to ask general spud cannon related questions.
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Unread postAuthor: Crna Legija » Sat Apr 07, 2012 4:09 am

Wont work, as soon as you fill via pilot valve the donut piston will get pushed passed the gap in the barrel then air will vent out if the barrel. You could how ever put a stopper to stop it going too far but the projectile wont move unless the back of it is exposed to pressure.
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Unread postAuthor: quark1980 » Sat Apr 07, 2012 4:39 am

err, you can put a spring behind the piston, the equalisation hole is there to prevent what you say.... alternatively you could fill from the pilot side, and make a bumper on the chamberside...

the projectile will always be in front of the pressure, hence the "odd" shape...

why wouldnt it work?
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Unread postAuthor: Crna Legija » Sat Apr 07, 2012 5:33 am

ahh k now i get what the grey thing is now i though it was the projectile, still the piston will get pushed forward passed the gap because it wont equalize quick enough but a stopper will make it work out.
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Unread postAuthor: quark1980 » Sat Apr 07, 2012 8:52 am

yeah, the stopper wasn`t in the drawing, but is indeed neccesary...

ah whell its just my idea to make a compact easy to use plinker....
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Unread postAuthor: Selador » Sat Apr 07, 2012 12:28 pm

Ok, I guess it's back to the old "gut" build. Where I build it the way my gut tells me to build it.

It's worked before, hopefully it will work this time.


I'd rather be using a 3/4" or 1" barrel, inside the 2" chamber.

But I have limited myself to the 1/2" barrel because I have such an easy, replenishing, and basically to me... free, source of dart material for the 1/2" barrel.

I have already begun the build, and have desided to go with a piston that rides in the chamber itself, instead of trying to work a 1" piston into the equation. I'm already going to have alignment/squaring issues at the barrel end of this thing. No need to introduce them at the pilot/barrel seal end.

Here is the beginning of that piston. A 1-1/4" end cap. Wrapped with enough tape to make a slightly less than snug fit. (Large enough gap to allow air past on inflation, but small enough not to just allow all the air back past it when the pilot chamber is emptied.)

The tape used is 10mil plumbing repair tape. If that proves to be not suitable, I'll use gorilla tape, instead.

A short, (longer than the cap itself.), piece of 1-1/4" pipe will be cut and glued into the cap, and then filled with foam or something, to try to cut down on the pilot volume.

More pics as I progress.
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