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Caveman simple HiPressure rifle...

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Unread postAuthor: POLAND_SPUD » Wed Jan 13, 2010 6:09 pm

Especially when using 750psi...
well yeah but the question is whether it's better to have a BV or a QEV as the pilot valve
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Unread postAuthor: MrCrowley » Wed Jan 13, 2010 6:11 pm

POLAND_SPUD wrote:
Especially when using 750psi...
well yeah but the question is whether it's better to have a BV or a QEV as the pilot valve

Yeah, Major Collins said to swap the ball valve for a blowgun. Granted, if the blowgun was on a smaller QEV that wouldn't be so bad but from what I've read it seems that the ball valve out performs the QEV pilot valve...
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Unread postAuthor: POLAND_SPUD » Wed Jan 13, 2010 7:33 pm

yeah it seems... but the two hasn't been compared in a proper test..

how can you know that the thing that lowered performance on QEV + blowgun combo was the QEV not the blowgun (the piloting valve of the piloting valve lol)?

my logic is simple... if the QEV is better for the main valve than the BV then why would it be worse as the pilot valve ?
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 14, 2010 12:58 am

POLAND_SPUD wrote:my logic is simple... if the QEV is better for the main valve than the BV then why would it be worse as the pilot valve ?


Maybe because the ball valve opens and stays open, irrespective of flow, piston bounce etc.
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Unread postAuthor: psycix » Thu Jan 14, 2010 8:33 am

POLAND_SPUD wrote:my logic is simple... if the QEV is better for the main valve than the BV then why would it be worse as the pilot valve ?
This is my theory on a QEV.
As a main valve, the air cannot escape freely, causing a lot of pressure available to push the piston back. Also, the flow is limited to the speed of the projectile, limiting the venturi "sucking" .
On top of that, the pilot area should be emptied faster then the main chamber through the barrel, preventing piston bounce.

As a pilot valve, there is only a little bit of air that escapes directly to the atmosphere. This results in a smaller push on the piston:
Pressure drops quickly, flow is high, so high venturi, and the "chamber" dumps incredibly fast, possibly faster then the pilot area, causing piston bounce.
In short: the low "chamber" volume and the unrestricted venting to the atmosphere have negative effects on the QEV's behavior.

The ball valve opens independent of pressure, it opens always just as fast (or slow), and when open, it stays open.
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 14, 2010 8:56 am

psycix wrote:The ball valve opens independent of pressure, it opens always just as fast (or slow), and when open, it stays open.


Image

:P :D
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Unread postAuthor: jeepkahn » Thu Jan 14, 2010 10:01 am

POLAND_SPUD wrote:
how can you know that the thing that lowered performance on QEV + blowgun combo was the QEV not the blowgun (the piloting valve of the piloting valve lol)?



Trigger pull to firing time suffers due to the piloting of the pilotvalve if a blowgun is used... but mainvalve speed suffers if you use too small of a qev to pilot the mainvlave because qevs are inherently restrictive(about 45% cv) and a largish bv(1/2") only has to open about 10-15% to flow more than a 1/4 qev because of it's large cross section... Just imagine if I used my big 1.5" Butterfly valve to pilot :twisted:

A qev/pistonvalve can't be beat as a main valve because it opens so violently and is normally(at least in my guns) larger than the barrel so the 45%-65% flow is never noticed, but a pilotvalve needs as large of a flow as it can get(because pilots are normally SMALLER than the pilot chamber)... So by using a bv thats larger than the qev it replaces you increase the rate at which the pilotvolume is expelled(in essence to pilot a mainvalve faster than a 1/2"BV you would need a 3/4"qev)...
And if you look at the volume of a qev, it's quite large compared to a bv, so you increase the pilot volume of the mainvalve by using a qev as well...
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Unread postAuthor: POLAND_SPUD » Thu Jan 14, 2010 2:26 pm

ohh dammit I've just noticed that the link I posted on the first page is wrong...

here is the right one

but you might as well click here instead.. it's web based not a .pdf file

sorry they have two models of QEVs... I opened both of them when I was writing that post and I accidentally posted the other one

now getting back to the topic... assuming that it really performs worse I think it can be either caused by

-excessive pilot volume that you've mentioned (and also the internal volume of 'chamber' side of the QEV, which, in this case, = pilot volume of the main valve... yeah I know that's what you said)

-what psycix said (yes jack... we know that's what you said :wink: )

if it's the first reason I guess it could be improved with the use of clippard's JLEV-F4M4 or JEV-F2M4 (QEVs with male thread on 'chamebr port'; they are also quite compact so their internal volume is also quite small)
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Unread postAuthor: psycix » Thu Jan 14, 2010 2:29 pm

-what psycix said (yes jack... we know that's what you said Wink )

Which was what I said.

psycix on the page before this one wrote:While the ball valve just opens slowly (and not even completely), it stays open, making sure the piston of the 1/2" doesn't bounce.

See, I said it first. :D
So I say: jack just said what I said, and I said that too! ;)

Say, I think I can say that this becomes pretty confusing, she said. Don't you say so as well or have you already said that? :roll:
I say the word said, before I said the word say.
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Last edited by psycix on Thu Jan 14, 2010 2:38 pm, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 14, 2010 2:36 pm

Fine, what WE said! :D
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Unread postAuthor: jeepkahn » Thu Jan 14, 2010 2:48 pm

jackssmirkingrevenge wrote:Fine, what WE said! :D


:sign3:

Seriously though, Back on topic you lackeys....
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