MJVO-3 venting air from the sides

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Fri Jul 17, 2020 5:36 pm

Hello Spudfiles! I've been working on a new cannon which uses a QEV piloted by a Clippard MJVO-3. Unfortunately during my initial pressure test at 100 psi, when I fired the cannon, air vented from the two holes on either side of the MJVO-3 instead of into the QEV and out the barrel as intended.

The "out" port of the pilot connects to the "P" port on the QEV. Port "A" on the QEV has a secondary air chamber, and "R" connects to my barrel. The "in" port on the MJVO-3 has a quick connect fitting which attaches to my HPA tank and regulator.

Have I connected the valves in an improper fashion, or am I using inappropriate parts for this build? My intention is for it to shoot 3/8 in steel shot, potentially at 300 psi, but I want to get my cannon operational before going to higher pressures.
Here is the entire cannon
Air cannon overview.jpg
And here is a closer look at the valve configuration
Air cannon valve closeup.jpg
Any help is appreciated! Thanks.
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farcticox1
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Sat Jul 18, 2020 5:11 pm

Components look good, you are filling from trigger valve (P). This is how I run mine
QEV.jpg
Trigger valve is normally open then blocks air feed and dumps P port to atmosphere to fire QEV. I think maybe you need to flip the connections on the MJVO-3. Hmmm, now I look at the connection diagram it appears as if you have it correct. Almost like the QEV is stuck, is the air getting into chamber ?
Untitled.png
Untitled.png (12.08 KiB) Viewed 925 times

Just finished a 10mm ball bearing launcher with homemade QEV, they do work excellently.
MFG (1).jpg
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jrrdw
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Sun Jul 19, 2020 4:25 am

The Clippard MJVO-3 is working as intended described by the manufacture. Under "Additional Information" on the product page it states "Exhaust-To atmosphere through holes in body.".

https://www.clippard.com/part/MJVO-3
Look if you must.
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jackssmirkingrevenge
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Sun Jul 19, 2020 6:36 am

jrrdw wrote:
Sun Jul 19, 2020 4:25 am
"Exhaust-To atmosphere through holes in body."
Don't we all :D
hectmarr wrote:You have to make many weapons, because this field is long and short life
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farcticox1
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Sun Jul 19, 2020 10:25 am

jrrdw wrote:
Sun Jul 19, 2020 4:25 am
The Clippard MJVO-3 is working as intended described by the manufacture. Under "Additional Information" on the product page it states "Exhaust-To atmosphere through holes in body.".

https://www.clippard.com/part/MJVO-3
Just what I thought, but he says air does not come out of the barrel, so the QEV is not QEVing ? or too much volume on the P side ?
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Sun Jul 19, 2020 12:02 pm

Thank you for getting back to me. I appreciate all of your thoughts!

I've independently tested my QEV using a slide valve, and it functions as expected; properly filling the secondary chamber and releasing air out the barrel. I even added more lubricant to the QEV to ensure the cylinder was properly cycling.

I also tested the MJVO-3 on its own (hooked up to my regulated pressure source), but I was having the same problem - air was only coming out of the side holes and was not being released through the "out" port of the valve.

I understand that the MJVO-3 releases to atmosphere in order to properly function, but I'm surprised that it is doing so without also releasing air from the "out" port. I could also try reducing the volume on the "P" side, but it is already fairly small.

I'm considering returning/exchanging my current valve. Could it possibly be defective? It seems to be the common variable in my tests.

@farcticox1 That's an impressive build! Thanks for sharing. I've been following your YouTube channel for awhile and you have true talent.
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farcticox1
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Sun Jul 19, 2020 2:29 pm

If the QEV is good it has to be that valve.
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