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Semi Auto

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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Semi Auto

Unread postAuthor: Lockednloaded » Tue Jan 05, 2010 5:28 pm

I have seen the slide valve+QEV combo work great on many semi auto cannons, and now i want to make one for myself. I wish to use a 3/4 QEV, but I am not sure what size slide valve would be sufficient for a proper pilot for good power. I can get ones as large as 1/2" but i don't want to go over kill. I would really like to use a smaller slide valve because they are cheaper and can handle more psi. I want to know how small a side valve i could use and not drastically hurt performance.

Your help is greatly appreciated,
Lockednloaded

UPDATE:
Design done in google sketchup, comments and critique appreciated
PS Breech area is actually black
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Last edited by Lockednloaded on Thu Jan 07, 2010 10:15 pm, edited 2 times in total.
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Unread postAuthor: PVC Arsenal 17 » Tue Jan 05, 2010 5:51 pm

I've used an 1/8" slide check valve on a 3/4" QEV with good results: http://s237.photobucket.com/albums/ff15 ... IM0719.flv

Be careful which ones you buy though. The ones you'll find in paintball stores usually only have one small port to drain the line. This isn't so good for fast piloting of a QEV. Such was the case on the valve I used in the video. Before I drilled three additional holes it vented the pilot volume VERY slowly. Keep in mind that if you do have to drill holes, you will need to clean up the holes so that you don't slice up the o-rings in the valve core. (Which, in case you were wondering, CAN be replaced by removing the retaining (snap) ring at the non-hex end of the valve core. This lets you remove the slide which holds the o-rings and will allow you to access the core which is where you will be drilling holes. Be careful with the core, much of the length is essentially a sealing face for the o-rings.)
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Last edited by PVC Arsenal 17 on Tue Jan 05, 2010 5:58 pm, edited 1 time in total.

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Unread postAuthor: jackssmirkingrevenge » Tue Jan 05, 2010 5:56 pm

What about these toggle valves for filling/piloting, does anyone have any experience with them?

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Unread postAuthor: PVC Arsenal 17 » Tue Jan 05, 2010 5:56 pm

@JSR- I've used similar types of valves before. My favorite was the Clippard MJVO-3. It's a 3-way, normally OPEN valve. The "open" part is very important. I've also used the Pneumadyne A11-31-44. Same function but slightly lower performance.

The great part about both of these valves is that they accept a thumb paddle style actuator sold by Pneumadyne which makes for a VERY nice trigger. Click the link in my signature to see a gun featuring the MJVO-3 with a paddle trigger.

I suspect, though, that these types of valves would need to be supplemented by a smaller QEV to help vent the main QEV.

I think a typical 4-way could work as well. You could make use of the extra output somehow, (CYLINDER) or just plug it up.

Image

Right column shows the Clippard valve above the Pneumadyne valve.
Left column shows 1/8" Clippard and Pneumadyne QEVs.
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Last edited by PVC Arsenal 17 on Tue Jan 05, 2010 6:10 pm, edited 1 time in total.

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Unread postAuthor: Lockednloaded » Tue Jan 05, 2010 6:05 pm

im not planning on going to a paintball store i am actually looking at any one of these http://www.fastenal.com/web/products.ex?N=999603569&in_dim_search=1 I'm glad 1/8" works because that one can handle 230 psi. On another subject, can i fill through the slide valve, or do I need a separate fill port. On a totally unrelated note, how do y'all get your words to be hyperlinked?
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 05, 2010 6:11 pm

Interesting. Do they do them to higher psi?

(url=http://www.fastenal.com/web/products.ex?N=999603569&in_dim_search=1)slide valve(/url)

Replace the round brackets with square, and you get slide valve ;)
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Unread postAuthor: Demon » Tue Jan 05, 2010 6:12 pm

Is anyone having a schematic of a QEV-slide valve combo? There are none on google and i am not sure to understand how to work.
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Unread postAuthor: PVC Arsenal 17 » Tue Jan 05, 2010 6:13 pm

Yes, you can fill right through the slide check. That's the neat thing about using them. In the "forward" position they will fill your gun. In the "back" position they will cut off the air supply while venting your gun's pilot volume (causing it to fire)

Here is a helpful diagram to learn how they work: Image

And to hyperlink words,
Code: Select all
[url=typetheURLhere]typethewordhere[/url]
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Unread postAuthor: Lockednloaded » Tue Jan 05, 2010 6:44 pm

Thanks for all your help, just so I'm sure of what I'm doing here this is what it will do right: I fill chamber through slide valve/QEV; load magazine; operate slide valve and get x amount of shots with y amount of pressure/volume of chamber.
And how much pressure would i need to get about six good shots from an 8" long 2" pipe?
Interesting. Do they do them to higher psi

I really don't know what you are saying, sorry
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Unread postAuthor: Demon » Tue Jan 05, 2010 6:52 pm

Here is a helpful diagram to learn how they work:


http://www.milsimlabs.com/rapid%20mortar.htm

So then, how this slide valve gun works? The slide is not connected to the air chamber ?
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Unread postAuthor: psycix » Tue Jan 05, 2010 6:52 pm

Wow, those toggle valves look awesome. I've never seen anything like that.
Another thing on my "machine this one day" list.
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Unread postAuthor: Lockednloaded » Tue Jan 05, 2010 7:00 pm

Demon that mortar is what has inspired me to make this, and the slide valve connects to the qev not directly to the chamber.
I have made my list for things i need to buy for the "Valve Section" of the gun, chamber and barrel will be figured out once someone tells me what material i will need to get six shots out of it without a huge chamber. here is My List
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Unread postAuthor: PVC Arsenal 17 » Tue Jan 05, 2010 7:11 pm

Demon wrote:
Here is a helpful diagram to learn how they work:


http://www.milsimlabs.com/rapid%20mortar.htm

So then, how this slide valve gun works? The slide is not connected to the air chamber ?


Certainly looks like it. If not, the only other thing I know of that could make it function that way is simply disconnecting and reconnecting a quick disconnect coupling repeatedly to fire and fill. Slide valves basically do the EXACT same thing, but they allow you to keep everything connected as one.

@Lockednloaded: The link you gave to your shopping cart does not allow any of us to see the items you've added to your own cart. That's something only you can see. If you'd like help, list the links to each individual item.

And as far finding how many shots you can get from a certain cylinder... I'm not the guy for that... I'm sure someone here can help.
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Unread postAuthor: Solar » Tue Jan 05, 2010 7:16 pm

I am wondering about those rated pressures on the fastenal slides, seems very low. Typically in paintball we have 800-1200psi (regulated 1st stage from 3000) going through a remote hose and slide check. From just the design, I would guess that 1200psi would be the max the orings could handle and still be able to slide easily. FYI, the Clippard MJ valves are fantastic and are rated at 300psi. I have had them to 700 with no problems.
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Unread postAuthor: Lockednloaded » Tue Jan 05, 2010 7:22 pm

whoops, sorry forgot that you can't see that, here you go:QEV,Reduce Bushing,Connecting Nipple, and Slide Valve they go in that order
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