First Airgun

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
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Alster370
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Mon Feb 21, 2011 9:50 am

Hi guys this is my first build so go easy on me. javascriptemoticon(':D')
Im looking for some feedback which will hopefully make my next build a lot better, what I have currently identified is that my air chamber is too small. I can pump it to 140psi in 3 pumps and I don't get any leeks. Although air seems to stay inside the pump so when I take it off there is a small pop.

what do you think?

bigger picture, although the end cap has been cropped out

http://s785.photobucket.com/albums/yy14 ... nt=089.jpg

Edited by jrrdw.
Last edited by Alster370 on Sun May 15, 2011 1:50 pm, edited 2 times in total.
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AnotherSnappedLine
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Mon Feb 21, 2011 10:07 am

Looks great- simple like mine! What PSI do you expect to take it to?
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Alster370
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Mon Feb 21, 2011 10:11 am

Thanks, hopefully 200, but keeping it leak free was quite difficult. Probably will have to compensate with more psi because of my small chamber.
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Lockednloaded
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Mon Feb 21, 2011 10:19 am

You're right about compensating for chamber size with pressure, you should really get a bycicle shock pump and take it to 400 psi to get some real power
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Alster370
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Mon Feb 21, 2011 10:43 am

that was my plan, a 300 psi shock pump from JE James' cycles. I can get a good shot with darts at 70psi so im looking forward to when I can take it even higher. The reason I went for a small chamber is so that I wouldn't be spending ages to pump up the tank per shot. I can increase pressure by 40-45 psi per pump which I am happy with I know that will go down to 30 or so when I get my shock pump because It is smaller than the floor pump which I am using now.

I seem to be losing air from the pump adapter itself because it is the type which you push on. To correct this maybe I should get a pump which has a screw on adapter which hopefully will stop the air loss.

Edited by jrrdw.
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Crna Legija
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Mon Feb 21, 2011 11:16 am

how much volume is the chamber, because i realyl bout you will get 30psi per pump from a shock pump i have a colax with about 30ml volume and it takes 25-35 pump to get to 350psi. also use the edit butten
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AnotherSnappedLine
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Mon Feb 21, 2011 12:37 pm

As obvious as this sounds, have you tride squeezing the connection between the pump adapter and fill valve? Mine leaks to but stops when pressure is applied.
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Alster370
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Mon Feb 21, 2011 1:08 pm

It sorta fixed itself now, I was pumping at 160psi in 5 pumps although I have to jump on the handle to force the air in :D. My air chamber is 15mm diameter and is 6" long. I was shooting bolts with tape wrapped around them and I was making some very large dents in metal sheets.

P.S Il upload a video tommorrow

quick question, what is the max rated pressure of compression fittings? I want to make sure they are up to the job when I make the change to 400psi

Edited by jrrdw.
metalmeltr
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Mon Feb 21, 2011 2:40 pm

your good, they will hold, actual pressure rating it likley around 150psi, they can take muck more no problem
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Alster370
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Mon Feb 21, 2011 2:45 pm

I will try and make a nice stock to go with it, because on the performance side Im pretty chuffed. But I think aesthetics is where it is let down, in my opinion of course.

:Edit: sorry for the double posts :(
Last edited by Alster370 on Mon Feb 21, 2011 3:28 pm, edited 1 time in total.
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jrrdw
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Mon Feb 21, 2011 2:51 pm

Image

Stop double posting, use the edit button if no one has posted under you.
Look if you must.
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Alster370
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Tue Feb 22, 2011 5:45 am

Jigsawed a MDF stock this morning, haven't attached it properly yet but took a few shots with it and there are no major problems. It isn't finished yet so keep that in mind. And yes I did attached it with tape as I have run out of zip ties.

http://s785.photobucket.com/albums/yy14 ... nt=003.jpg

http://s785.photobucket.com/albums/yy14 ... nt=002.jpg

http://s785.photobucket.com/albums/yy14 ... nt=001.jpg
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Crna Legija
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Tue Feb 22, 2011 5:54 am

to up the power a bit and make shots more consistence use a spring to open the ball valve
'' To alcohol... The cause of, and solution to, all of life's problems.”
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Add me on ps3: wannafuk, 8/11/11 cant wait
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Alster370
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Tue Feb 22, 2011 3:09 pm

Good news! I fixed the leak in my air gun. Turned out to be the way the valve had been inserted into the cap. So i took it out, squeezed some bits of rubber over the valve then pushed it back in. It took a long time because it was such a tight fit. The only small leak is one of the compression fittings and that can be fixed with a tightening and some Teflon.

Tomorrow I am going to quadruple my chamber size, from 5" to 20". So that the ball valve isn't moved too far forward im going to put a 10" chamber then a flexible hose to mount the other 10" underneath if that makes sense.
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Gun Freak
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Tue Feb 22, 2011 5:15 pm

Putting a hose on is going to reduce your flow, although on such a small chamber, it probably doesn't matter.
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