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Help with a mini piston coax

Discuss miniature cannons built from things such as pill bottles and pen caps.
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Help with a mini piston coax

Unread postAuthor: brplatz » Sun May 04, 2008 9:16 pm

i needed help cause i cant find a good way to get the piston working consistently or at all sometimes for my little pneumatic.

suggestions would be great

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Unread postAuthor: Sergeant Dotson » Sun May 04, 2008 9:20 pm

Ha, when I saw it, I thought that it was the piston. :lol: Let me be the first to say very cool. I'm afraid that I cannot help you with the actual piston though. Mini pistons make me mad because they are so hard to get to work.
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Unread postAuthor: brplatz » Mon May 05, 2008 7:58 am

thats funny it does look like a piston for one of my larger guns. :) i have tried many hot glue and wood pistons but cant get any to seal right or they are hard to get the equalization holes right.
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Unread postAuthor: spudman029 » Mon May 05, 2008 11:50 am

have you tried using a small bolt with a metal and rubber washer?
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Unread postAuthor: rcman50166 » Mon May 05, 2008 12:03 pm

Actually this is quite convenient. I also am having a problem with the seal on my pneumatic coaxial. The piston is made of a VERY small nylon spacer with hot glue in the middle as the seal against the barrel. It leaks. I'm wondering if I should add a spring on the pilot side of the piston to add more pressure against the seal, possibly closing off the leak. If that won't work how does using silicon caulk sound for the seal? The seal face won't be any larger than an airsoft bb. I need something flexible, durable, small, and plentiful. I'm also considering the seal on the inside of soda bottle caps.
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Unread postAuthor: hyldgaard » Mon May 05, 2008 12:11 pm

A piston cast from hot glue worked fine for me in my 6mm coaxial. probably as simple as it gets :)
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Unread postAuthor: Sticky_Tape » Mon May 05, 2008 12:39 pm

Not enough pressure what are the pressures you are using? I found for my marker gun see my signature that if I didn't use enough pressure the gun didn't work that's why I made a high pressure pump.
EDIT: What is the pilot volume and pilot valve is the pilot valve a shrader?
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Unread postAuthor: brplatz » Mon May 05, 2008 3:41 pm

i have only tried a hot glue piston valve as of now

i went only to 50 psi so far.
what about equalization holes? they should be on the outside of the piston?

yes the shrader is the pilot valve and the fill valve, not much room for another valve and i was hoping to not have to build a pilot setup(ball valve+shrader and such) trying to keep it small and simple.

i was also thinking that you could make many of these then use them as ammo or something. have a hammer to pop the shrader valve
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Unread postAuthor: Sticky_Tape » Mon May 05, 2008 4:17 pm

That was thought of before. You should use higher pressures like 300psi if the gun can take the pressures. Actually you don't need any equilization holes the piston isn't suppost to seal 100% the air should just seep past the piston. If the piston has a equilization hole and you have a large pilot volume then the shrader will most likly not be a adequate enogh to move the piston very much.How big is the gap bettween the shrader and the piston? In my Marker gun there is a small gap maybe .5cm. If there is a gap you can make it smaller by lenthening the piston.

EDIT: in that threaded plug on the back is there a dimple that is about a inch deep? That would definently make the pilot voume larger that's why I didn't use pre made fittings in mine I used epoxy ask JSR.

EDIT #2: Is there a rubber sealling face on the front of your hot glue piston? If there isn't then the 50psi you said wouldn't be enough to push the piston hard enough to make the piston seal therefore letting all the air or most to come out the barrel not leaving enough pressure in the gun to pilot the piston or push it back.
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You can tell how awesome a cannon is by the pressure used.
http://www.spudfiles.com/forums/high-pr ... 12803.html
xnt rnm ne z ahtbg
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Unread postAuthor: brplatz » Mon May 05, 2008 6:25 pm

ok i tried it a 100 psi no luck!

so i changed to a different piston. this one with a rubber sealing face and a hot glue body. no equlization holes. screw it on and add the pressure and no leaks, but when i press the shrader to release the pilot there is nothin.

ill do some more tweakin but any hints are great

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Unread postAuthor: Sticky_Tape » Mon May 05, 2008 7:07 pm

brplatz wrote:ok i tried it a 100 psi no luck!

so i changed to a different piston. this one with a rubber sealing face and a hot glue body. no equlization holes. screw it on and add the pressure and no leaks, but when i press the shrader to release the pilot there is nothin.

ill do some more tweakin but any hints are great

I tried 160psi with my marker gun and guess what no luck!
you need high pressure air ether make a pump that creates high pressures or buy one with small pneumatics it esencial learned that the hard way after 3 rebuild of the marker gun I saw on this website you need to use higher pressres I was pissed but it pays to look around.
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You can tell how awesome a cannon is by the pressure used.
http://www.spudfiles.com/forums/high-pr ... 12803.html
xnt rnm ne z ahtbg
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Unread postAuthor: brplatz » Mon May 05, 2008 7:33 pm

ok i made a different piston and at 100 psi it works! but the power is severely lacking. i believe there is a hole where the barrel sticks through my homemade "bushing". and i cant find my epoxy :x
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Unread postAuthor: Sticky_Tape » Mon May 05, 2008 7:36 pm

Did you look at my Marker gun brplats? I made a vid if you look you can see atabout 5 feet it easily pierces bristel board still I say you need more pressure. 300psi-400psi

EDIT: On second look at your gun I don't think it can handel those pressures I'm not going to tell you to scrap it like other members would but I think you should make one out of somthing other than pvc maybe copper and if you do make a copper one you can pollish it!
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You can tell how awesome a cannon is by the pressure used.
http://www.spudfiles.com/forums/high-pr ... 12803.html
xnt rnm ne z ahtbg
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Unread postAuthor: brplatz » Mon May 05, 2008 7:45 pm

Ok cool but im not sure the pvc can handle that kind of pressure.
maybe its time to move to a metal one since i got plenty sittin around.

what kind of pump do you use to get those pressures?
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Unread postAuthor: Sticky_Tape » Mon May 05, 2008 7:48 pm

I used a home made copper pump.
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You can tell how awesome a cannon is by the pressure used.
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