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My 3" piston, 2" porting GB 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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Unread postAuthor: kablooie » Sat Mar 01, 2008 2:18 am

Hi all, sorry to get back too late school can really get in the way of tuber (or gold ball) destruction. I like the tee in that it allows me to use that threaded endcap so I can reuse the schrader (money and rides are hard to come by) but I get you point about reduced pilot. Next time i will just cough up the money and do it that way, but for now the power is already too much for my shooting range.

The chamber is that size because as you guessed, I am limited with a bike pump. I do have a 10 pound CO2 tank, so as soon as I get a safety pop-off valve (1800 psi is scary) I will make the chamber bigger. I intentionally used the male adaptor on the chamber so when needed I could expand the chamber volume.

Yes, the peanut butter jar is skippy, and has worked very well for me so far (last two words there are key). The duct tape does get slightly torn after use, but It works very well with vaseline as the lube. I tried wrapping the tape around the jar first, and that created a very uneven surface, so on my second try I taped it lengthwise, being careful to make the smallest seam possible, and using two layers. eventually, I will most likely make an epoxy piston which would be easier to maintain.

The foam shrinking had not occurred to me, I guess my pilot volume is that much bigger than i thought it was. Oh well, I am okay with that, at least until I become even more of a power crazed maniac.

Thanks for all the positive feedback and advice!
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Unread postAuthor: jrrdw » Sat Mar 01, 2008 7:39 am

Check out the pilot volume on mine, I don't worry a bit about it. 2" diameter by 1' long. If someone where to do the math, we are probly close to even.

Image

Here it is with the sprinkler valve. Adds a little more volume because of the adapters.

Image
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Unread postAuthor: kablooie » Sat Mar 01, 2008 2:55 pm

Nice cannon, I guess the pilot volume is only really a detriment if you are trying to suck every last bit of power out of your cannon. I am lacking a space big enough to make that necessary so I will leave it alone for now.

@Carlman, fluorescent paint is not very intimidating, but in my opinion it is better without it (a little more macho).
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Unread postAuthor: kablooie » Sun Mar 02, 2008 11:56 pm

I have figured out on google earth (if that is at all accurate) that my cannon fires ~333 yards, nearly 1/5 of a mile. That was at 40 psi and at a really low angle (less than 45 degrees). I now have outgunned my shooting range.

Does anybody know a good place to shoot spuds in the San Francisco Bay area? I am stumped.
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