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new guy here, not my first 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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new guy here, not my first cannon

Unread postAuthor: cox_rango1 » Sun Jun 22, 2008 10:54 pm

I have built 2 others but this is by far the largest and i think most destructive i've built.

version 1.0

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failed pressure test at 20psi, bad glue job on one of the 90's

version 2.0

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what do you all think?

also open to opinions and suggestions on modifications

specs are as follows:

2 - 4"x3' side chambers
1 - 4" inspection 'T'
1 - 4" - 2" reducer
1 - 2" ball valve
1 - 2" - 2.5" adapter (custom)
1 - 2.5" x approx 6' barrel
1 - 200psi pressure gauge
barrel preset at 45*

has been tested to 125psi with no leaks

range test not yet performed, er...range not confirmed, we lost sight of the tennis ball mid flight..... :lol:

total air volume not yet calculated estimating around 4-5gallons
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Unread postAuthor: rp181 » Sun Jun 22, 2008 10:58 pm

125PSI in that? O.o

Its practically all DWV, does it have a pressure rating on it?
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Unread postAuthor: cox_rango1 » Sun Jun 22, 2008 11:00 pm

its all sch40 PVC, 220psi rated i believe
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Unread postAuthor: biggsauce » Sun Jun 22, 2008 11:02 pm

Well as a suggestion, build another cannon. Your tee, 90's, and reducer are not pressure rated. Its just a safety issue. These things can be dangeous if not built right.

You're on the right track though. People will tell you the same about the safety issue, and make suggestions about a faster valve. Search for "piston valve tutorial" or "how to modify a sprinkler vavle"

A faster vavle will gve you much better performance on that new cannon...
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Unread postAuthor: cox_rango1 » Sun Jun 22, 2008 11:05 pm

we are in the process of modding the sprinkler valve within the next week or so

as far as the 90's, tee, and the reducer, what pressure rated alternatives are out there? i was under the impression they were rated materials

also we don't plan on ever going over 90psi, our tennis ball test was at 90 and it far out performed what we were looking for
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Unread postAuthor: TwitchTheAussie » Sun Jun 22, 2008 11:08 pm

DWV is not pressure rated. It is good for "shock" pressure such as a combustion but is dangerous under held pressure.
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Unread postAuthor: MrCrowley » Sun Jun 22, 2008 11:16 pm

Nice cannon, shame about the DWV though. You can check what fittings and pipe are infact pressure rated by reading this article:
http://www.spudfiles.com/spud_wiki/inde ... _Rated_PVC
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Unread postAuthor: mister pointy » Sun Jun 22, 2008 11:18 pm

All the dwv parts you used are available in nsf-pw pressure rated pipe, including the 90's, the tee, and reducer bushing. even if your fittings are supposedly pressure rated, their short socket depths could cause them to blow apart, just salvage what you can from that cannon and build a new one.
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Unread postAuthor: biggsauce » Sun Jun 22, 2008 11:18 pm

http://www.sprinkler.com/buy/sch40_tees_slip


heres a start. 4" pressure rated fittings are harder to find at say, Home Depot ( they dont have them )

Maybe scale down your chamber diameter, or make it an over under because Home depot has encaps, couplers and bushings that are all 4" pressure rated
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Unread postAuthor: cox_rango1 » Sun Jun 22, 2008 11:19 pm

edit: post was made prior to reading link above

after examining my cannon, the chambers are pressure rated, the NSF-PW, is printed on them

whats stores carry the pressure rated tee's, 90's etc?
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Unread postAuthor: jr » Sun Jun 22, 2008 11:41 pm

as for a store..... ?? Just read the fittings they will say "nsf-pw" right on them usually near the size marking....

Nice monster you got there.. as noted..please find rated fittings there is a lot of volume there and if it shatters( like pvc does) it could be ugly..
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Unread postAuthor: cox_rango1 » Sun Jun 22, 2008 11:48 pm

yeah we had to scrap version 1.0 due to a side chamber blowing off the tee at only 20psi and it went a good 10ft from the rest of the setup when it did

ill look for the pressure rated fittings asap, we don't really mess with our cannons that often so its not a big deal, and i'm pretty good with a cutoff wheel so i should be to separate the sections and salvage most of if not all the pressure rated 4"

oh by the way, figure all might get a kick out of our future planned projectile, i am an automotive tech, and one day while working on a chrysler van doing a full HVAC job i had to replace the receiver/dryer, took the old one off and noticed it.....the perfect projectile...

just under 2.5" wide, 6" long, aluminum slug, rounded tip...will post pics soon,
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Unread postAuthor: battlemonkey » Mon Jun 23, 2008 1:59 am

Nice looking cannon, shame about the DWV though.
I've had the same thing with a bad batch of glue, my cannon came apart at 40PSI and put a hole in the wall.
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Unread postAuthor: cox_rango1 » Mon Jun 23, 2008 5:34 am

we were using the purple primer/clear glue combo

plumber friend of mine told me to use the clear cleaner, and blue glue (the stuff that will dry under water), much more confident in its holding strength
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Unread postAuthor: biggsauce » Mon Jun 23, 2008 8:08 am

You're going to have some trouble finding pressure rated 4" fittings at a local store. Try making your chamber diameter smaller, the fittings are easier to find and are cheaper.
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