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QEV semi auto option?

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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QEV semi auto option?

Unread postAuthor: Crna Legija » Sat Mar 06, 2010 6:49 am

i just order one of these qevs and want to make a semi/full auto marble gun

i wanted to know wich set up would give me semi/full auto.
i have research for a a few day and found that pop offs give full auto. and hammer valves give semi is then a way to have both semi and full

does a qev and 3way do it ? if so what type of three way is need i have one with 3 ports 2 normally open and 1 closed

i will be useing a blow forward breach
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this is the 3way valve
IMG_0042.JPG (28.25 KiB) Viewed 1586 times
IMG_0041.JPG
this is the BFB its made out of pn12 pvc and has a drill press lathed piston made from some hard black plastic
IMG_0041.JPG (28.88 KiB) Viewed 1586 times
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Unread postAuthor: Patto » Sat Mar 06, 2010 12:48 pm

No a qev and 3way doesn't give you full auto because if you held the trigger open it will only release air not recycle the bolt
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Unread postAuthor: POLAND_SPUD » Sat Mar 06, 2010 1:31 pm

yeah you'd get a semi auto... if you want to get full auto you'll need something that closes the circuit on/off a couple of times per second

taht can eitehr be a 555timer circuit or an off the shelf timer relay...

you can see the timer relay I got here
http://www.youtube.com/watch?v=6cErmwrg6LI

and here used with the gun
http://www.youtube.com/watch?v=wHDmZYGSjjo

there are smaller ones as well (more less the size of a box of matches) but I never really wanted a full-auto gun so I bought the cheapest one I could get



what type of three way is need
normally open
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Unread postAuthor: Crna Legija » Sat Mar 06, 2010 8:53 pm

Is there a valve that was have 2 pilot port both narmaly closed and a pop off in one and other just for semi? and i could swap betewn them.

it would need 4 ports
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Unread postAuthor: POLAND_SPUD » Sat Mar 06, 2010 10:15 pm

uhmm it seems I should write a how to on 3 way valves and stuff like that...

ok so you have a couple of 3 way valves.... are all of them solenoid valves??
if they are solenoid valves then you can use a simple electrical switch
when you press the button the solenoid will open the valve (piloting the gun)...

if you want to achieve full auto you need to use a simple switch that would send the signal through a thingy (555 timer/timer relay) that would convert that continuous signal into, let say, 5 short impulses per second...

so as long as the trigger is pressed it sends 5 short impulses to the solenoid and the solenoid opens and closes the valve 5 times per second as long as the trigger is pressed


you won't need two switches you just need one for the trigger and one to choose between semi auto (directly to the solenoid) and full auto (to the solenoid but leading through a 555 timer/timer relay)


I tested an idea that would allow to achieve full auto without the need to use batteries and solenoids...
to cut a long story short... the thing needs an air piloted 3 way valve valve (just like a 3 way valve but one that switches when you send air to its piloting port... when you remove it (vent) it returns to its original position thx to spring return)
and it switches itself from one position to the other several times per second


damn you might even mod a solenoid valve... essentially it's similar to modding a sprinkler valve... (note that this only works if your solenoid valve is an indirect acting valve)

there are really a lot of ways to achieve full automatic fire...
but if you want to use DCV valve you have to understand them... they are not that complicated as they seem they are just different...

you can find some most interesting info here
http://www.clippard.com/downloads/gener ... matics.pdf

not everything there is relevant but I think you should read all of it anyway...

if you have any questions just write
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Unread postAuthor: Crna Legija » Sun Mar 07, 2010 10:53 am

i think im going to go semi with a hammer valve. i read the stuff you posted and thought the im never going to use full auto is would be cool but kind useless. would it work with out constant flow im using a 1.5l FE at 200 psi

thanks for the help
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Unread postAuthor: c11man » Sun Mar 07, 2010 11:08 am

a 3 way valve and a qev would alow you to fire with all the air in the chamber, if you got a 5way you could use that to have it fire only using part of the pressure in the chamber.
of course both those would have a constant air it.....
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Unread postAuthor: Crna Legija » Sun Mar 07, 2010 11:10 pm

thanks for that i was just looking at normally open 3ways, in that case i will be making a hammer valve pilot like btbs old shatterhand.

edit: dose anyone know how big how a hammer valve i should use, would a blow gun with out lever work ?
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Unread postAuthor: POLAND_SPUD » Sun Mar 07, 2010 11:42 pm

well you can find more info here -> http://www.spudfiles.com/forums/directi ... 20438.html

have a look at the pic there...that's basically all you need to get achieve semiauto with a QEV gun (ignore the loading mech there... all you need is a QEV gun + a 3 way NO valve)


Alternatively, as I said earlier in some thread, you can get the same result that BTB achieved on his shatterhand but without a hammer valve...
(that is multiple shots from air stored in the chamebr only... though it does not give you extra air or more shots in any way.... you just keep all air in the main chamber instead of having a separate tank, which might be useful but not in every case)

you'd have to mod the QEV to be filled from the chamber side... then attach a 3 way NC valve to the pilot side of the QEV and attach a small chamber for vented air.. in this way you would get good consistency

Though, I don't think that that would be simpler than just using the QEV + 3 way valve combo... you just have to buy a ready made product and attach it to the pilot side of the QEV... it's really that simple
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Unread postAuthor: Crna Legija » Mon Mar 08, 2010 12:09 am

the main thing i want is for it to be portable so i think the a hammer valve will be easy and effective way of doing it, tho if a 3way does it with out constant flow i would do it that way.

i know i have to mod the qev for chamber fill and put a spring in for a hammer valve multi shot.
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Unread postAuthor: POLAND_SPUD » Mon Mar 08, 2010 12:29 am

This is more less what I had in mind. AFAIK no one has ever built something like this but I guess there is nothing that suggests it won't work

Though I think that a simple QEV + 3 way valve is better :)
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Unread postAuthor: Patto » Mon Mar 08, 2010 1:59 am

poland - so say with your last diagram ^^^ you say when you release the trigger it vents from the 3 way so can you use that air to make blow back ? is there enough pressure or volume ?

sorry if i missed something :?
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Unread postAuthor: POLAND_SPUD » Mon Mar 08, 2010 2:52 am

well sort of... it would be possible to use air vented from the pilot side of the qev so the air cylinder should be attached to the small chamber that is supposed to keep that vented volume...

that's how one could build a gun similar to BTB's shatterhand but without a hammer valve... as I said earlier it is not the same thing as a simple QEV + 3 way valve combo

personally I am not a big fan of modding QEVs in order to fill them from the chamber side.

Lol I couldn't do that to my QEVs, I won't perforate their pistons.. they are way too young for that... as you can guess law is a bit different in the Netherlands :D :D :D
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Unread postAuthor: Crna Legija » Mon Mar 08, 2010 5:30 am

i tryed to pilot my homemade piston valve with a blowgun hammer valve it worked but wont re seal fully still goes shhhh, i think the barrel port isn't 100% level cut. i bought a cap gun a copyed the parts in metal and will use as the hammer ill post a pic later.

thanks for all the info poland, defiantly come to use on another project but i think its a bit essayer to make a hammer valve + qev and cheaper. my valve should be here in 7-10 warking days
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Unread postAuthor: POLAND_SPUD » Mon Mar 08, 2010 5:40 am

I am very lazy so I the design I mentioned does not require much work..

anyway time will tell... at least you know what to choose if you run into problems
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Last edited by POLAND_SPUD on Mon Mar 08, 2010 6:20 am, edited 1 time in total.
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