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Extreme Shock pump problems

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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Extreme Shock pump problems

Unread postAuthor: VH_man » Sun Nov 08, 2009 7:46 pm

well, in my re-discovery of spudgunning I have decided to fix my shock pump so that it actually works. Problem is, I have tried 100's of ways to make a check valve work. and for some reason I just cant do it.

I assume that basically, I want to seal off the bottom of the pump tube, and have a rubber poppet that is pushed against it by a weak spring..... this just simply wont work for me. Either that or it will work to 300 PSI and then fail, which is bad for reasons we all probably know.

If you desire pictures of my current setup I can draw one up, but any chance I could get input on some designs that actually work?
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Unread postAuthor: mark.f » Sun Nov 08, 2009 9:30 pm

Well, have you tried a ready-made check valve?
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Unread postAuthor: cannonmaster » Sun Nov 08, 2009 11:03 pm

possably a different configuration or like mark.f said a already made check valve would be a good idea
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Unread postAuthor: jackssmirkingrevenge » Sun Nov 08, 2009 11:06 pm

Use a schrader as a check valve? Doesn't get more ready made than that, and if you fiddle with the spring you can reduce the minimum volume needed to "crack" it.
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Unread postAuthor: Gippeto » Mon Nov 09, 2009 1:12 am

Pictures of your current setup would provide information about any special requirements. (size, orientation, etc.)

More information on how exactly your checks are leaking might yield a solution as well.

Some pics of check valve designs. :)

http://www.tpub.com/content/engine/1410 ... _101_4.jpg

And a pic of one of the checks I built. It's good to 9000psi. :wink:

No spring in this one, it relies on orientation to initiate the seal. The small threaded piece is drilled out to provide travel for the ball, and it also holds the o-ring in place under flow conditions.

Have you tried the check valve in my stirrup pump how to? It's always worked reliably for me ... past 400psi.
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Unread postAuthor: Mitchza89 » Mon Nov 09, 2009 1:39 am

That's it. I'm finally going to get off my bum and share my gift with the world. The schrader valve used as a check valve for a stirrup or shock pump. With a pump that has 1/2'' tubing, just grind the bulk of the rubber but keep enough so that it will make an air tight seal with the tubing. Next is to fix it in place with the tubing. I drilled a small hole through the tube and valve about 10mm from the bottom (Absolutely make sure you don't drill through the pin of the schrader) and inserted a hardened steel nail to keep it in place.Keep enough nail on both sides of the tube to allow a compression olive to be kept in place and not slide. This prevents a blow out of both the schrader valve and the tube at very high pressures.

I found this was the best, easiest and cheapest way to make a good pump check valve. With the pump cylinder being held in place by brass compression and threaded fittings, it's very easy adapt the pump into a gun, hose, gauge....whatever really...

I'll post tomorrow a complete guide to making both 1/2'' shock pumps and 3/4''.

Thanks all,
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Unread postAuthor: VH_man » Mon Nov 09, 2009 6:38 am

hrmm... you guys have given me a few good ideas. I will try them when I have time.

@Gippeto: my check valve setup looks exactly like the bottom right valve in the link you posted. almost exactly. and for some reason It doesn't work...

@Jsr: Last time I tried a schrader the cracking pressure was far too great. Im using a very small-bore pump shaft so I can reach pressures of 600 PSI (hopefully), and therefore I have to keep dead space to an absolute minimum.

That and I have tried ready-made valves, and they all seem to have far too much dead space.

Right now, I think I might try re-molding my old valve setup (as I think I mixed the epoxy wrong, which may be part of my problem) and maybe modifying a ready-made valve to work for my purposes.

Picture of my setup will be on the way too. It reduces dead space to almost zero If you manage to make it work (unlike me)
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Unread postAuthor: john bunsenburner » Mon Nov 09, 2009 10:42 am

Hmm...if one culd get rubber balls in 1-8mm diameters that would make GREAT checks...
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Last edited by john bunsenburner on Tue Nov 10, 2009 11:58 am, edited 1 time in total.
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Unread postAuthor: blackhawk13 » Mon Nov 09, 2009 1:56 pm

john bunsenburner wrote:Hmm...if one culd get ubber balls in 1-8mm diameters that would make GREAT checks...


you mean like this

http://www.airsoftgi.com/product_info.php?products_id=4647

i suggested that but he said that the pressure would be to high. what about a piston with a weak spring holding it? just like a piston valve but no pilot
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Unread postAuthor: Gippeto » Mon Nov 09, 2009 2:40 pm

If you're using epoxy to hold the check in or together...that's likely at least part of the problem.

Compressing air creates heat, which is the death knell for any epoxy I've ever heard of.

Threaded connections, or solder (preferably a higher temp solder) are the tickets to success, safety, and longevity.
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Unread postAuthor: VH_man » Mon Nov 09, 2009 3:44 pm

Gippetto, I looked over your tutorial once again and I think I may attempt this. It seems to be that I could easily build this into my setup without much trouble AND not worry about catastrophic failure.
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Unread postAuthor: Brian the brain » Mon Nov 09, 2009 5:47 pm

Get a QEV.
The kinds I use.
Tap a small hole into the piston next to the seat.
Put a spring behind the piston.
Voila...you now have a modded QEV.

Put your pumptube on the barrel port,
Plug the pilot
Attach T with hose and gauge to the " chamber" side

Voila
You have turned a modded QEv into a robust checkvalve.
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Gun Freak wrote:
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: VH_man » Mon Nov 09, 2009 6:05 pm

Brian the brain wrote:You have turned a modded QEv into a robust checkvalve.

I have thought about this, and the only problem I see is the evil dead space issue.

you do have another point though... A piston valve is basically a check valve, with minor changes. Knowing this, I can presumably just build a piston cannon that "fires" into my pump chamber.... which would work perfectly. not to mention I have yet to make a piston valve that doesn't work, So If I construct it the same way I wont have troubles.
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Unread postAuthor: far_cry » Wed Nov 11, 2009 6:23 pm

this is my shock pump .there is 2 picture of my homemade check valve

http://www.spudfiles.com/forums/my-second-shock-pump-full-diatelas-t18650.html
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Unread postAuthor: VH_man » Wed Nov 11, 2009 6:50 pm

Thank you very much. this basically tells me exactly what I need to do.
Nice pump By the way..... Im jealous.
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