problem with qev rifle

[twizi]

i have made a rifle that has a 1/2 qev from fastnel its piloted by a 1/4 qev. witch i want to pilot by a modded blow gun. but i see that it the best when i just disconet the quick connect fitting from the 1/4 qev has any body experinced this problem with their gun.
and if you have how do i fix it

[rikukiakuchiki777]

Are you saying that when you disconnect the quick connect, it actuates the QEV? If so, install a ball valve after the quick connect as a safety feature, so before disconnecting the quick connect you shut off the ball valve, and only the air between the ball valve and connect gets vented.

I hope this was relevant

[Ragnarok]

@rikukiakuchiki777: Better option - a check valve. No need to remember to shut it.

[rikukiakuchiki777]

Ah my bad, I never even though about a check valve. That would definitely be better, Thanks rag

[Hotwired]

Mmm, I was getting pissed off at the poor performance of the check valve in the bike valve I used for my cannon during mid-construction testing so I added a proper check valve which cured all problems.

[twizi]

no i mean i need a good pilot for a 1/4 qev a modded blowgun is giving worse prformance then if i just disconect the qc fitting

[Hotwired]

That sounds like fun.

I'm piloting a 1/2" QEV with an unmodified blowgun (the internals are stock) on the end of 30cm of 8mm copper tubing and it works fine.

Why did you add the 1/4" to the 1/2" QEV and how can you tell it's worse with the blowgun?

Logically it will pilot better by simply taking off the QC fitting because that has a much larger flow than the convoluted and restricted path through the blowgun.

I wouldn't have thought that would affect it much especially with a QEV piloted QEV, when the pressure hits a certain level the 1/4" should pop and immediately vent the 1/2".

Is there a massive pilot volume in this?

[rikukiakuchiki777]

no i mean i need a good pilot for a 1/4 qev a modded blowgun is giving worse prformance then if i just disconect the qc fitting

I'm only guessing, but a poppet valve maybe? or a push-button valve?

[twizi]

i was think that but i mean i heard those valve had less flow then a modded blow gun
no there is no massive pilot same as your probaly

[rikukiakuchiki777]

I'm not sure about the flow rate, but there is only one way to find out

[twizi]

i just tried with a ball valve got same result still not fully open

[MrCrowley]

i was think that but i mean i heard those valve had less flow then a modded blow gun
no there is no massive pilot same as your probaly

A quick connect plug attached to the QEV, when disconnected from the quick connect socket, it will have far greater flow than that of a blowgun. I find blowguns are pretty poor pilot valve unless they're on a sprinkler valve or on a 1/4" QEV attached to a 1/2" QEV


edit:

i just tried with a ball valve got same result still not fully open

The 1/4" QEV or the 1/2" QEV didn't fully open? You must have a massive pilot volume, can you post a picture?

[twizi]

i will try tommorw had a long work day but it has a 1/8 stanless steal tube. i think ten inches and it goes to a blow gun and check valve my 1/4 qev is a diagram the 1/2 piston
looks like heal but tryin to make it a semi

[qwerty]

What type of blowgun are you using because i had one that had less flow than a schrader! if you are using those red trigger ones i would try taking away the 1/4 QEV and putting the blowgun there instead it worked fine in mine and it wont change the performance that much.