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barrel sealer ,probs?

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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barrel sealer ,probs?

Unread postAuthor: FORE!!!! » Wed Aug 12, 2009 5:46 pm

well yesterday i decided to build a 1'' barrel sealing piston valve,after finding an aluminium rod/piston in the shed. ive attached a neoprene sealing face which is held together by a bolt, the bumper has a washer and 2 o-rings.
refill is via a quick connect ,with a pressure gauge,, my question being im using a 1'' modded sprinkler valve as the pilot exaust ,is that to big?

and does the weight of the piston affect the performance,being a solid 60mm
long, 25mm diameter aluminium piston?

would a 3/4 barrel be too big for performance issues??
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Photo 140.jpg
barrel sealer
Photo 139.jpg
other view
Photo 142.jpg
the piston, i put another piece of neoprene at the opposite end of the piston sealing face,so basicaly the bumper is 2 pieces of neoprene
the other being on the seat ,should that have a prefect seal??????
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Unread postAuthor: jor2daje » Wed Aug 12, 2009 6:06 pm

I think as long as your piston is a good fit it is hard to have a pilot valve too big.
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Re: barrel sealer ,probs?

Unread postAuthor: jackssmirkingrevenge » Wed Aug 12, 2009 6:43 pm

FORE!!!! wrote:my question being I'm using a 1'' modded sprinkler valve as the pilot exhaust, is that too big?


With pilot valves it's simply a case of the bigger, the better - given your less than optimal pilot volume, I would say you have an appropriate pilot valve.

and does the weight of the piston affect the performance, being a solid 60mm long, 25mm diameter aluminium piston?


Technically a lighter piston accelerates quicker and opens faster.

would a 3/4" barrel be too big for performance issues?


As long as the outside diameter isn't too close to 1" you should be fine.
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Unread postAuthor: inonickname » Thu Aug 13, 2009 3:57 am

Technically a lighter piston accelerates quicker and opens faster.


And retains less energy, resulting in less stress on your cannon.
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Unread postAuthor: FORE!!!! » Thu Aug 13, 2009 5:45 am

thanx for the responses ,also i have a small fire extinguisher i bought from bunnings today to use as the pressure vessel, i was cheering untill i undid the valve and realised its a metric thread, im wondering if anyone else has used a fire extinguisher and managed to find a metric to imperial nipple ,would the local plumbing supplies stock such a fitting?????
if not has anyone got any ideas??
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Unread postAuthor: jmadden91 » Thu Aug 13, 2009 5:49 am

FORE!!!! wrote:thanx for the responses ,also i have a small fire extinguisher i bought from bunnings today to use as the pressure vessel, i was cheering untill i undid the valve and realised its a metric thread, im wondering if anyone else has used a fire extinguisher and managed to find a metric to imperial nipple ,would the local plumbing supplies stock such a fitting?????
if not has anyone got any ideas??


Lol I did the same thing :evil:

I know McCrowley has used them and had them welded on. Maybe thats a possibility?
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Unread postAuthor: jackssmirkingrevenge » Thu Aug 13, 2009 6:20 am

I'm sure that if you look around you can find a metric/imperial adapter
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Unread postAuthor: jmadden91 » Thu Aug 13, 2009 6:26 am

Not sure if this is one or not. Not exactly sure what its adapting :?

http://www.bellpro.net/xcart_program/home.php?cat=271
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Unread postAuthor: inonickname » Thu Aug 13, 2009 6:33 am

If you find me the exact pitch of the threads, size etc I'll turn you an adapter if you can't find one.

(pm if interested, I probably won't bother asking for payment).

You can also weld, or use epoxy.
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getting there

Unread postAuthor: FORE!!!! » Thu Aug 13, 2009 7:57 pm

well after visiting the local plumbing supplies and found out that they dont supply that type of thread,i decided to just cut the top of the fire extinguisher
leaving me with just the thread which i silver soldered to 3/4 threaded brass elbow its works perfectly now,and dam its powerfull!

my final problem to a perfect weapon is that the sealing face leaks a lil ,does
anyone have any ideas on getting a perfect seal?? my neoprene sealing face rest against a clean cut copper pipe using tube cutters ,which has been lighty
filed with a smooth file ,it dosent get any flatter????
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Attachments
Photo 143.jpg
elbow with welded thread on one end to attach pressure vessel
Photo 144.jpg
there she is
Photo 145.jpg
the pipe used i need a better seal
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Re: getting there

Unread postAuthor: Technician1002 » Thu Aug 13, 2009 9:05 pm

FORE!!!! wrote:my final problem to a perfect weapon is that the sealing face leaks a lil ,does
anyone have any ideas on getting a perfect seal?? my neoprene sealing face rest against a clean cut copper pipe using tube cutters ,which has been lighty
filed with a smooth file ,it dosent get any flatter????


Get a piece of stick on sandpaper in a fine size. Cut a circle and stick it on the end of a dowell the same diameter as the piston. Insert and rotate. When done there should be no sign of any file marks. All the sandpaper marks should be very fine and travel around the barrel seat, not crossing it making leakage paths. It works for me.

Don't overlook other possible leakage paths such as along a bolt that fastens the neoprene to the piston face. It is often a source of leaks.

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finshed product

Unread postAuthor: FORE!!!! » Fri Aug 14, 2009 12:53 am

tech ur a champ ,i found some 1000 grain buffing sandpaper,and it a 100% perfect seal, it was a nightmare trying to sand steel pipe,so i went and got a copper barrel
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finished product
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Unread postAuthor: jackssmirkingrevenge » Fri Aug 14, 2009 12:56 am

Good to hear, now let's see those damage pics :D
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Unread postAuthor: FORE!!!! » Fri Aug 14, 2009 1:06 am

Tommorow is saturday so ill make a video with pics,i have to go to the bush to shoot it cause the last time i let off a couple of rounds with my previous pneumatic my kind neighbours decided to dob me in to the police :evil:

anyways sit tight 8)
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in action

Unread postAuthor: FORE!!!! » Sun Aug 16, 2009 4:15 am

just a short video of it in action

http://www.youtube.com/watch?v=_STbSEme52Q


115psi shot at 15mm ply hitting a 25mm mdf board ,cant really go any higher with the sprinkler valve cause she blows at 120psi
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