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Sneak Peek (56K Warning)

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 » Thu Mar 26, 2009 1:18 pm

Image

Image

Image

Image

All I have left to do is add O-rings, lubricate, and seal up. This is all you're getting. :) The cannon it's going on will have to wait until I finish it.

This is my first time successfully fitting an entire 1-1/2" porting piston valve in a 2" tee. I resisted the urge to spike it into the ground after I made the last weld...

That's it.
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Unread postAuthor: Gippeto » Thu Mar 26, 2009 1:28 pm

Nicely done Mark, very neat construction. (New way to make o-ring grooves ?)


With clear primer, it would be perfect. :)
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Unread postAuthor: jeepkahn » Thu Mar 26, 2009 1:32 pm

Gippeto wrote:With clear primer, it would be perfect. :)


BURN!!! :D

Nice lookin' valve though...
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Unread postAuthor: mark.f » Thu Mar 26, 2009 1:36 pm

Yeah, I figured I'd be painting it, so I didn't really worry about the clear primer.

Besides, ever since McMaster stopped carrying it, I have had a hard time trying to find it reasonably priced, or sold in single cans. I figured I could just paint over it (and I am).

The O-ring grooves are simple: a 3/16" wall x 2" OD O-ring sits over 1-1/4" pipe, and a piece of coupler and the 2" fender washers hold them in place. Major props go towards clide for this method, which I got looking at his golfball valve and other early projects.

We'll see if it works when my O-rings get in (something I couldn't find locally, after several days of searching). I suppose I should probably get off my butt and go pick up some grease, but I'll probably wait for that too.

Thanks for the criticism (I mean that in the true sense of the word).

P.S. - it's very hard to type, since I hacked a chunk of meat off my left index finger. :)
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Unread postAuthor: psycix » Thu Mar 26, 2009 5:27 pm

Oeh that gap between the sliding tube and valve seat looks a short (read: flow restrictive)
The valve is nice, but you just HAVE to use a longer piston and a shorter sliding tube.
D/4 does NOT APPLY to a barrel sealing T valve.
D/2 or more would be better.
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Unread postAuthor: mark.f » Thu Mar 26, 2009 6:29 pm

psycix wrote:Oeh that gap between the sliding tube and valve seat looks a short (read: flow restrictive)
The valve is nice, but you just HAVE to use a longer piston and a shorter sliding tube.
D/4 does NOT APPLY to a barrel sealing T valve.
D/2 or more would be better.


It's not 1/4 of the barrel diameter, it's more like 3D/8. On this project, I was willing to sacrifice a little power (read: not much) for looks, and that was the best I could do with the tools I had and the materials I had at my disposal. I doubt there would be much if any performance increase if I were to lengthen the opening distance to half the barrel diameter, and then I would have to rebuild another valve and lengthen the carriage pipe to extend out of the tee, and that would not look nearly as good.

I've included the plans I was going off of when building this. In the diagram, 1px = 0.01". In the 2" pipe in the rear, I have to fit 1.) A plug, which counts for 3/16" for the o-ring groove, about 1/4" for the bolts, and 3/8" for safety on both sides of the bolts (3/4"). Plus, I have to fit in a 1/4" bumper, the opening distance, and the length of the piston that needs to remain sitting in the carriage pipe to stay aligned and sealed. I don't see much more opening distance I could squeeze out of this setup.

EDIT: also, the valve is a little tilted to the side in that last picture, so the distance might look a little shorter than it actually is. The measured distance (not from the diagram) is about 1/2" (0.504", but that's not too reliable), so it would be about 0.31 times the barrel diameter.
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1px = 0.01". Dimensions taken directly from measurements of the fittings I used.
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Unread postAuthor: c11man » Thu Mar 26, 2009 8:01 pm

cool valve AND diagram

cant wait to see the preformance with this valve!
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Unread postAuthor: mark.f » Sat Mar 28, 2009 1:44 pm

Well, round two. :lol:

I'm ordering some clear primer (as per Gippeto's suggestions) from sgort next week sometime, and rebuilding the valve.

I'm also going to install some sort of check valve in the piston, and redo the back plug to house 1" female threads in-case I want to install a sprinkler valve for the pilot (probably off of my BudGun). I don't have a 1" NPT tap, and they're pretty expensive, so a threaded bushing is the ticket.

Watch this thread sometime late next week for v.2 (actually, version 3, but we won't go there)...
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Unread postAuthor: c11man » Sat Mar 28, 2009 1:50 pm

your just going to scrap this one and build a new one?

if so i will take this one. :shock:
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Unread postAuthor: mark.f » Sat Mar 28, 2009 1:59 pm

Well, not completely scrap it. I'm going to finish assembling and test it, to make sure the overall layout works nicely, and then after a little testing, start work on the new one.

Where's the fun in taking this one? :wink: All you need is a hand saw and belt sander to make it...
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Unread postAuthor: c11man » Sat Mar 28, 2009 3:18 pm

i know they are easy to make i just dont have the cash right now

the fun is in shooting the cannon :)

edit: building is also very fun
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Unread postAuthor: Velocity » Sat Mar 28, 2009 5:06 pm

I talked to you in the PM's, but not here, so here goes...nice valve :wink:

Your building style is very similar to mine...make something decent, realize there is a small cosmetic problem, and build another one to fix the problem...I've currently gone through 4 of these types of valves for one reason or another...number 4 is going strong though :roll:

If you need any parts for this new valve...the offer still stands...good luck!
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Unread postAuthor: clide » Sat Mar 28, 2009 9:54 pm

Looks good. Glad to see other people using my o-ring technique.
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Unread postAuthor: mark.f » Sun Mar 29, 2009 1:20 am

Yes, I'm surprised more people haven't. It's very easy as far as construction, and should offer good seals when coupled with a little teflon tape.

And yes, Velocity, our building style does get a little expensive. :oops:
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Unread postAuthor: mark.f » Mon Mar 30, 2009 9:34 pm

Well, damn.

I wanted to test this valve tonight, but apparently O-rings put a lot of force on the groove walls when compressed into a piece of pipe with moderate "squeeze" on the rings.

The 2" metal washer on the back plug (seen above) was sanded and epoxied to the actual plug itself, and cured for 24 hours, to form the back of the groove. Slipping an o-ring into it, I greased it up and then pushed it into the 2" pipe (took a good bit of force), and then "pop", the washer parted with the plug, and now I have to epoxy up another plug.

I might just wait until I build the finished valve to fix this problem. Except the timetable has been pushed back a little (lot), due to issues I really don't want to talk about right now. You'll see it when it's finished.
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