Qev problems

A place for general potato gun questions and discussions.
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jackssmirkingrevenge
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Mon Apr 29, 2013 5:36 am

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Reason: Fixed video.
hectmarr wrote:You have to make many weapons, because this field is long and short life
Filippo.san
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Mon Apr 29, 2013 6:04 am

Haha problem solved! Ok, seriously, that didnt change a lot..
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jackssmirkingrevenge
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Mon Apr 29, 2013 6:33 am

You now have a vertical air feed, meaning you can have an in-line bolt.

Just like most PCPs:

Image

http://www.arld1.com/mechanismpumppneumatic.html
hectmarr wrote:You have to make many weapons, because this field is long and short life
Filippo.san
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Wed May 08, 2013 7:13 am

ok. I've finished my gun and it works very well. what can I use for the trigger instead of a blow gun?
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jackssmirkingrevenge
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Wed May 08, 2013 7:23 am

Modified ball valve:

Image

Image

Or any of a multitude of valve styles really, what's wrong with the blowgun?
hectmarr wrote:You have to make many weapons, because this field is long and short life
Filippo.san
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Wed May 15, 2013 8:45 am

There's a big waste of air, i have to find something different or a small blow gun. And i have to use it reverse or it will leak
Filippo.san
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Thu Jun 13, 2013 6:41 am

Ok. my gun is finished and it works fine. have you got some better ideas for the scope mount? it's not very stable.. I'm also looking for a better scope, maybe a 6x32 or something like that. my budget is about 40 euros. Any suggestion?
thank you in advance.

ps what's the highest pressure i can reach with this gun in your opinion?

http://i44.tinypic.com/2vd4pp2.jpg
http://i42.tinypic.com/30netqg.jpg
http://i39.tinypic.com/2vv598k.jpg
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jackssmirkingrevenge
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Thu Jun 13, 2013 7:06 am

Image

Image

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I wouldn't take it past 400 psi, the blowgun will probably start to leak above that pressure.

The breech looks awkward, does it seal well?
hectmarr wrote:You have to make many weapons, because this field is long and short life
Filippo.san
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Thu Jun 13, 2013 12:52 pm

Yes, there are no air losses. And what about the scope mount?
Should I use a rail maybe?
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Thu Jun 13, 2013 12:57 pm

You can buy a couple of these and clamp them directly to the barrel:

http://www.ebay.com/itm/DUAL-WEAVER-RAI ... 3cd20e3be0

Note that the above fits a weaver rail, your scope might need a different type of rail.
hectmarr wrote:You have to make many weapons, because this field is long and short life
Filippo.san
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Thu Jun 13, 2013 1:08 pm

Ok thanks. I'm happy with this gun- I hit a can at 60m!- but I'm thinking of modifing it. What do you think I can change to get a more powerful and more accurate gun. I'd like to say that I've reached 700km/h with 1g pellets.. But that's not enough and I need more accuracy too!
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Thu Jun 13, 2013 1:16 pm

Moar power -> more pressure! What are you running at now? A fridge compressor will fill that massive chamber to 400 psi easily.

For accuracy, the important thing is to be consistent. Always fill to the same pressure, always pull the trigger with the same force, make sure your projectiles fit precisely in the barrel, and make sure your scope is securely mounted to the barrel.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Fri Jun 14, 2013 1:44 am

Hi,i'm new here so i hope i have posted in the correct place.I am buildind a gun similar to Filippo.san.The qev i am using is the cylindricl type 1/4 bsp(about 8mm id)and 1/4 bsp fittings also 8mm id.The exhaust port is about 20mm long,the entrance(where the seal sits) is 7mm and the outlet is 8mm?My barrel is 6.35mm.Is this qev ok?Should i drill it out to be a uniform 8mm or leave it?I'm trying to work out these qev's.Also can i fill from chamber side or pilot side?Am i correct in saying i must drill a small whole in the qev seal on the outer of the sealing face So that the pressure will equalize and a spring on the pilot side to close the valve.I have been doing my homework but need a little help.i would also like to thank everyone for a great site,much appreciated,thankyou.
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Fri Jun 14, 2013 1:51 am

jpalf1 wrote:Is this qev ok?
yes
Should i drill it out to be a uniform 8mm or leave it?
Leave it as it is, more than enough flow for your barrel size.
Am i correct in saying i must drill a small whole in the qev seal on the outer of the sealing face So that the pressure will equalize and a spring on the pilot side to close the valve.
Only if you want to fill from the chamber side.

Filling/triggering from the pilot size using a three way valve is one of the easiest and most efficient solutions.

http://www.spudfiles.com/forums/semi-au ... 23626.html
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Fri Jun 14, 2013 3:57 am

Thankyou Jackssmirkingrevenge,on the pilot side of the qev i can put a tee fitting and use a blowgun and schrader valve or quick connect fitting.I wanted the pilot area to be small as possible so i wouldn't waist too much air.I still don't understand,wont this method empty the air chamber with one shot?How will the valve reseal after the first pull of the trigger?
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