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help with 1/4" QEV gun. even shots.

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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help with 1/4" QEV gun. even shots.

Unread postAuthor: jmez1996 » Fri Feb 18, 2011 5:35 am

i have recently put together a new gun using a 1/4" QEV i got off ebay. a blowgun as a pilot and a ballvalve between tanks to allow multiple shots.
the gun isnt finished im just getting it together.. im gonna make a wood stock etc. later

i pump the primary tank (the lower longer one) upto about 230psi then open and close the 1/4 ball valve to allow multiple shots. or i open the ballvalve slightly to allow semi-auto

my only problem is that the first shot is really strong and makes a loud noise from the blowgun... then the second is slightly less strong.. then the third is pretty weak.. and then it starts to get too weak or just wont pilot..
is there anyway to make these shots more even. and allow more than 3-4 with my setup or anything i could change.. i dont want to use an external air source though..
any help would be appreciated.. cheers :)

[/img]
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Attachments
18022011375.jpg
the current setup.
18022011373.jpg
showing the tank and barrel.
18022011374.jpg
the entire setup so far...
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Unread postAuthor: jackssmirkingrevenge » Fri Feb 18, 2011 5:52 am

You can:

- ditch the secondary chamber, and mod the QEV with a spring and equalisation hole

- replace the blowgun with a slide/spool/DCV/whatever POLAND_SPUD is calling them these days :D

Both options will let you eliminate the ball valve too.

How hard are you pulling the blowgun? Have you tried pulling it very slightly? It should give you more shots for the same power.
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Unread postAuthor: jmez1996 » Fri Feb 18, 2011 6:05 am

okay yeh ive heard about modding the QEV that way but never seen a post about it in all the hours ive spend on spudfiles..

also what about using wyz2285's method? using a mod to the blowgun?
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Unread postAuthor: jackssmirkingrevenge » Fri Feb 18, 2011 6:16 am

jmez1996 wrote:okay yeh ive heard about modding the QEV that way but never seen a post about it in all the hours ive spend on spudfiles...


Brian used one here.

also what about using wyz2285's method? using a mod to the blowgun?


You mean this one?

Image

If I got it correctly, it basically adds a pop-off element to the blowgun, limiting the piloting and conserving air.

The same effect could be achieved by using a hammer valve to operate the QEV, or just using careful trigger finger control to operate it lightly. The latter is something you can try out with your current setup.
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Unread postAuthor: jmez1996 » Fri Feb 18, 2011 6:24 am

yeh thats the one.
i might give that a go because i like my current set up and have a good stock that i can fit too it.
let me kno if you come up with any other ideas.
cheers.
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Unread postAuthor: nature-boy » Fri Feb 18, 2011 7:23 am

IMO the most elegant solution would be adding a regulator between the main reservoir and the smaller chamber.

Building a hammer-valve as the pilot would also be an option, because of the self-regulating nature ( I learned that on SF...) of them, like BTB did in his "Old Shatterhand", but I never did that, so I can't tell whether that works well.
BTW, "using careful trigger finger control" never worked for me...

Although I don't really think that modding the qev with a spring and filling from chamber-side would help that much with more even shots, I would recommend that too, because you will save pilot volume (what in fact will give you also more shots...), your gun will have a better look/ergonomics and be more compact ....aaand if you place the ball-valve between the main reservoir and the smaller chamber and open it just a little bit, you won't have to open and close it anymore in between shots. That's what I did on this gun.
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Unread postAuthor: Gun Freak » Fri Feb 18, 2011 7:31 pm

Depending on your barrel length you could shorten your seondary chamber to be able to fill it more times. Also you could close the filling ball valve before pressure equilizes to get more shots. Looks nice.
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