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my piston design

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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my piston design

Unread postAuthor: JDP12 » Wed Apr 23, 2008 11:34 am

hey all, i'm working on my piston gun, and this is the design i came up with. most of the detail is in the drawing, but the main concept in this is the slots in the front piece of the piston. I think that these will really help the guns actuating time because the air will be able to get to the barrel faster. i'm more looking for inputs on the slot design than anything else because i already know how to position the back o-rings so the piston seals before air can escape through the slots..

so opinions, suggestions??

<img src="http://i157.photobucket.com/albums/t79/justhavinagoodtime/piston.jpg?t=1208968792">
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Last edited by JDP12 on Wed Apr 23, 2008 11:40 am, edited 1 time in total.
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Unread postAuthor: Carlman » Wed Apr 23, 2008 11:38 am

i would comment if i could see but the little red cross is blinding me
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Unread postAuthor: JDP12 » Wed Apr 23, 2008 11:40 am

haha sorry carlman, its up now..

anyone?
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Unread postAuthor: Brian the brain » Wed Apr 23, 2008 12:05 pm

Sounds reasonable...but if your sealing face is flush with the bottom "channel"of the Tee, there would be no benefit.
The air could rush out immediately at the point the piston moves.. :roll:


If you think your design will give you better results you can build it.It doesn't seem faulty.
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: JDP12 » Wed Apr 23, 2008 12:10 pm

yea BTB, i'm not sure exactly where it will be yet, that diagram wasn't drawn too accurately. I realize your point, guess my drawing doesn't illustrate that too good. I guess depending on where the piston would be i might not need slots at all... I'm not sure yet.

Do you think it would be feasible to have the piston seal up against a bushing that is in the right tee socket instead of a pipe portruding into the tee like i have drawn, or is that not possible?

Only wondering because it could save me some dead space in my gun. so basically in this diagram the sealing face would just push up to the bushing. i'm concerned that may not seal however- what do you think?

this one isn't drawn too accurately either..

<img src="http://i157.photobucket.com/albums/t79/justhavinagoodtime/piston2.jpg?t=1208970972">
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Unread postAuthor: Brian the brain » Wed Apr 23, 2008 12:39 pm

Sealing face has to be smaller in diameter than the back of the piston in order to generate force to pull it open.
I guess you know that...

You will have to take a good look at the Tee you want to use and see if you can get it all to fit inside of the tee.
Hard to guess like this.

In Overkill ( metal) I put a short piece of pipe in a reducer, from the wrong side in, and threaded that into the back of the Tee.This way I have a good cilinder for the piston to move in, without snagging on the bottom Tee port, and got it all inside the Tee.

That did mean I had to scale down the piston in comparison to the Tee.
1 inch port- 1 1/2 piston, inside a 2 inch Tee.
Works very well.
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Can't ask for a better compliment!!
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Unread postAuthor: JDP12 » Wed Apr 23, 2008 1:59 pm

so are you saying the bushing wouldn't work?? I'm confused, isn't the sealing face almost always going to be smaller than the back because the pipe it seals against will be inside the tee so it will have to be smaller??
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Unread postAuthor: psycix » Wed Apr 23, 2008 3:24 pm

A somewhat nice idea it is, but why not make the front "slotted part" like this:


The bigger the slots, the better the flow.
And when are the slots the biggest?
When the areas that are not slotted are sticks.

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Unread postAuthor: JDP12 » Wed Apr 23, 2008 4:03 pm

haha true...

BTB- think you could draw up a quick diagram of how overkill's works??? I think i'm overcomplicating it..
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Unread postAuthor: unisonmind » Wed Apr 23, 2008 4:48 pm

Why don't you just glue a small peace of pipe into the back of the bushing-like this

<a href="http://s87.photobucket.com/albums/k154/unisonmind/?action=view&current=Picture068.jpg" target="_blank"><img src="http://i87.photobucket.com/albums/k154/unisonmind/Picture068.jpg" border="0" alt="Photobucket"></a>

if you use lasco fittings a 1 1/4 coupling fits good in a 2''x1 1/2''npt bushing
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Unread postAuthor: JDP12 » Wed Apr 23, 2008 5:09 pm

huh thats a good idea thanks!!
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Unread postAuthor: MrCrowley » Wed Apr 23, 2008 5:28 pm

I did the same thing as unisonmind on my SGA cannon. It makes things a lot easier.
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Unread postAuthor: LikimysCrotchus5 » Wed Apr 23, 2008 5:32 pm

I wasnt following this thread too much, but is that little lip in the picture the part that would seal against the piston's sealing face?

And isnt the bushing fully threaded? would you have to destroy some threads to get that pipe to glue it?
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Unread postAuthor: unisonmind » Wed Apr 23, 2008 5:37 pm

if your talking about my pic then yes the lip in the pic is the where the piston seals against


and no in the end of the bushing there is a small lip with no threads (well that is with the lasco fittings i don't know about other fittings)
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Last edited by unisonmind on Wed Apr 23, 2008 5:43 pm, edited 1 time in total.
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Unread postAuthor: MrCrowley » Wed Apr 23, 2008 5:38 pm

LikimysCrotchus5 wrote:I wasnt following this thread too much, but is that little lip in the picture the part that would seal against the piston's sealing face?
Yeah that's what it looks like. I always wondered why more people didn't do this, it allows you to have interchangeable barrels much easier. Otherwise don't you have to have a 'seat' on all your other barrels too if you do it the normal way?
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