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2" Tee Barrel Sealing Valve, help me please [pictures]

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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2" Tee Barrel Sealing Valve, help me please [pictures]

Unread postAuthor: theRIAA » Tue May 29, 2007 12:17 am

:oops: o..kay, so I've started a little project, a 2" Tee Barrel Sealing Valve (gun). like the one here...

http://www.geocities.com/izzydoesit_99/YASLA.html
http://www.geocities.com/izzydoesit_99/YASLA_Page2.html

and with similar video tutorial here:

http://www.bcvids.com/dload.php?action= ... d9cd37d066

I started making one a little different. I used a 2" to 1" reducer instead of a 2" plug. (to use a 1" sprinkler to activate) and I have run into some major problems. I want this gun to work, so I would appreciate your opinion on some things, the pictures are on flickr.

Here are the Pics:
http://www.flickr.com/photos/theriaa/se ... 280632120/
respond in the pictures or here, be sure to read the notes

and YES, I am willing to completely re-make all the valve parts/ change my design. please help
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Unread postAuthor: hi » Tue May 29, 2007 12:41 am

i can tell you exactly what the problem is, and that is the fact that your piston is:

1. not round, it must be a perfect circle or it wont work.

2. there is no bumper (that i saw)

3. the piston isnt very round

4. when seated, it should be a total of about 1/2'' from the exhaust, it doesnt need to slide back very far to work.

5. did i mention that the piston wasnt round?

a helpful tip:

mold a piston out of hot glue in another peice of pipe of the same diameter out of hot glue sticks. use a hot glue gun, i tried melting mine with a blow tourch and it didnt go so well. be sure that is you do it this way to first spray the mold pipe with PAM or something simular or that piston wont come out. good luck.
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you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Unread postAuthor: theRIAA » Tue May 29, 2007 1:58 am

i guess I will do the hot glue gun piston, but how do I seal the tee? just fitting it together, and screwing it together would leak like crazy, is glueing it closed the only way???
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Unread postAuthor: MrCrowley » Tue May 29, 2007 2:58 am

No you can get threaded adapters or do what I do and use an end cap bolted in with o-rings to seal it.
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Unread postAuthor: mark.f » Tue May 29, 2007 8:18 am

I see another thing. What diameter is the outlet pipe going to be?

Another thing is simply that that piston does not seal effectively in the track pipe, it looks like. Try building a longer piston, (with hot glue, as suggested above), or with 1-7/8" plastic rod either wrapped in duct tape to fit snugly, then lubricated with grease or petroleum jelly, (make sure to use nitrile gaskets if you do use petroleum jelly). Or, you could hand-cut or borrow a lathe to cut some O-ring grooves into the piston and install O-rings to seal. But... duct tape has worked just fine for me so far...

EDIT: as for the back plug, you can use a gasket between the reducer and the stop in the tee to seal off the outside edge of the gasket, then bolt it in with frequent and evenly spaced machine screws, coated in a thread sealant.
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Unread postAuthor: theRIAA » Wed Jun 06, 2007 11:30 pm

AHAHAAHAHAHAHHAHAHAHAHAHAHHAHAH
Image
Image
50psi, 6'' from barrel, drove 16 penny nail through 2x4 (with a blue shop towel stuffed down barrel) the barrel is 1" and like 6 ft long.

so I got it working...

i had to open, seal the screws with hot glue, and close it 5 times...
rebuild NEW HOT GLUE PISTONS 3 times...
and seal numerous leaks

but I got it working... and if you have no idea what im talking about...
http://www.flickr.com/photos/theriaa/51 ... 280632120/

It LEAKS AT A WELDED SEAM!!!!! though... my half assed 2" plug, to 1" 90 that leads out of the T, to the sprinkler valve.

any ideas on how to fix (cover up) glued seams? gorilla glue? PVC cement? Its just a small leak, I could get it up to like 75psi, but its really annoying.

If I cant fix the leak, ill just wait for my glue piston to destroy itself (no bumper) and replace that section (its the only replaceable section)

I'll add it to the cannons page in a week or so, after i clean my room

its late... im gon to bed
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Unread postAuthor: squeaks » Thu Jun 07, 2007 12:42 am

Okay, here is how you fix a leak. Epoxy! You can either get epoxy puddy or liquid 2-part epoxy. I recomend you get the 2-part epoxy since the liquid will form around the leak better. Use some soap and water to find the leak. Just pressurize the gun then dab the soapy water over the leaking joint. Then, mark the spots where bubbles come out, dry the joint off, and epoxy the leak. Make sure you get it nice and thick, so it won't leak again.
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