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compacting a tee piston

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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Unread postAuthor: mark.f » Mon Mar 29, 2010 8:55 am

Technician1002 wrote:1/4 the diameter applies where the air can enter the gap from all sides. In a T up to 2/3rds of the path is blocked by the body of the T. A larger opening will be required to keep the performance up.

It works well for coaxial designs. Even then I try to have the piston open at least 1/2 the piston valve seat diameter. I like the entrace to the barrel be the only notable restriction without a series second restriction of a small piston to valve seat gap.


I said at least. :wink: Space is kind of limited in a valve like this (where you're trying to fit everything flush with a tee), so I usually use about 3/8 of the barrel port.
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Unread postAuthor: Lockednloaded » Mon Mar 29, 2010 11:05 am

Do you think I could house the piston in the back plug? And what should I try to go by d4 or d2 or what?
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Unread postAuthor: velocity3x » Mon Mar 29, 2010 11:20 am

Lockednloaded wrote:And what should I try to go by d4 or d2 or what?


If you don't have room for a full retract (D/1), then "D/All you can get" is a formula that can go wrong.
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Unread postAuthor: mark.f » Mon Mar 29, 2010 1:22 pm

velocity3x wrote:
Lockednloaded wrote:And what should I try to go by d4 or d2 or what?


If you don't have room for a full retract (D/1), then "D/All you can get" is a formula that can go wrong.


Can go wrong? :D

I usually go for as much as I can get in these tiny tee valves. I'm currently drafting up another version to my old valve with slightly more opening distance and a check valve-type equalization scheme. Last time I took a drafting course was in high school, though, so I have to redo the drawings every day or so. :roll:

EDIT: and "D/All you can get" would get smaller. :wink:
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Unread postAuthor: Lockednloaded » Mon Mar 29, 2010 3:17 pm

So my plan is to house a cast hot glue piston housed inside of the back plug, but I'm afraid that the piston will get damaged by the screws, and i don't really have much room for a bumper

EDIT: Another idea i have:
Would a galvanized bushing be a good housing for a piston
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Unread postAuthor: Lockednloaded » Sat Apr 03, 2010 7:02 pm

sorry to double post, but construction has began, and i would like to post some pictures and recieve feedback.
this is just the front area so far, i now need a back plug and a piston.
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Unread postAuthor: mark.f » Sun Apr 04, 2010 1:07 am

Before you began this construction, did you have a list of part dimensions (lengths) written down?

Like I said, it's MUCH better to start with a plan so all you have to do is fabricate the parts and worry of nothing more than measuring.

That sealing face extends rather far into the tee. Space is going to be VERY limited in the back of the valve if you wish to have everything housed in the tee.
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Unread postAuthor: Lockednloaded » Sun Apr 04, 2010 9:55 am

well nothing is glued yet, i'm just laying out the parts for a general feel for things. For the piston housing, i'm totally baffled on how you got a peice of pipe so deep into you tee, because there is not just a lip, but the whole tee is thicker.
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Unread postAuthor: metalmeltr » Sun Apr 04, 2010 4:15 pm

About the only thing you can do is to sand it out with a dremel or a sanding drum in a drill.
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Unread postAuthor: iknowmy3tables » Sun Apr 04, 2010 5:26 pm

yeah you got to use a dremel, I found that hole saws can help in cleaning out a tee but you have to be careful to not end up cut through the tee especially if you aren't using a drill press
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Unread postAuthor: Lockednloaded » Sun Apr 04, 2010 7:13 pm

i think it would be easier for me to sand down the length of pipe that i will be using.
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Unread postAuthor: iknowmy3tables » Sun Apr 04, 2010 9:57 pm

alright as long as you have a lathe or belt sander
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Unread postAuthor: mark.f » Sun Apr 04, 2010 10:05 pm

I sanded down the length of 2" pipe on my valve with a belt sander, like ikm3t said. It took some time but worked fine, and I believe I could do a better job the second go-around.
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Unread postAuthor: Gun Freak » Sun Apr 11, 2010 4:24 pm

Sorry to dig up, but LnL, have you got any further on it yet?
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Unread postAuthor: Lockednloaded » Sun Apr 11, 2010 4:33 pm

well, just a little further on R&D. The only thing that has no plan yet is the piston. For sealing the back plug, i found this great sealing tape called "stretch n seal" or something, but it seals better than any of my attempts at o-rings.
But besides that, i've been preoccupied with my dueling piston, and a few other airsoft related launchers
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