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Qev problems

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Unread postAuthor: jpalf1 » Fri Jun 14, 2013 4:03 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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Unread postAuthor: jackssmirkingrevenge » Fri Jun 14, 2013 4:05 am

Here's the theory from another post:

This assumes you have two chambers - one small firing chamber, containing enough compressed gas for one shot, which is connected to the chamber side of the QEV (typically marked as "A"). You then have a larger main reservoir, which feeds into the QEV through the three-way valve which is connected to the pilot area of the QEV (typically marked as "P".

Basically something like this:

Image

When the valve is in the forward position, it allows air to flow from the main supply to the QEV and fill the pilot and firing chamber.

When the valve is in the rear position, two things happen:

- main supply is cut off

- QEV pilot chamber is open to the atmosphere, emptying it and firing the launcher

The valve goes back to the forward position (you need to add a spring or do it manually) and the cycle can be repeated.

This is the concept:

Image

The slide valve is basically a three way valve.

A three way valve has three ports, which we will call A, B and C

There are two possible paths, AB (with C blocked off) and AC (with B blocked off)

A is connected to the pilot area of the piston

B is connected to your main tank

C is simply left open to the atmosphere.

At rest, the three way is in position AB. This means your reservoir is filling the launcher chamber.

When the trigger is pulled, the valve switches to position AC. This means the reservoir is blocked off, and is no longer filling the pilot and chamber, while the pilot is exhausted to the atmosphere, which fires the launcher.

Once the trigger is released, the valve goes back to AB, refilles the pilot and chamber and the cycle can be repeated.
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Unread postAuthor: jpalf1 » Fri Jun 14, 2013 4:57 am

Thankyou again Jackssmirkingrevenge,i have seen these examples,but my air supply(soda stream bottle)chamber/ball valve,will be connected to the "A" port of the qev.i wanted to get a few shots out of it.i am presently stuck with a shock pump but intend on getting a fridge compressor and a hills mk3 pump(saving more cash).I can see how it works filling from pilot side,but not from chamber side.same as Philippo.sanThats why i askedabout drilling the hole in qev seal and spring on pilot side.(i.m still learning on computer otherwise i would put up photo)sorry.
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Unread postAuthor: jackssmirkingrevenge » Fri Jun 14, 2013 5:08 am

jpalf1 wrote:hats why i askedabout drilling the hole in qev seal and spring on pilot side.


This is pretty much what you have to do for your setup to work.

Instead of throwing money at a Hills pump, have you thought of making your own?

Gippeto has an excellent tutorial on how to make one using off-the-shelf parts here: http://www.spudfiles.com/forums/easy-st ... 13277.html
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Unread postAuthor: jpalf1 » Fri Jun 14, 2013 6:30 am

Yes, i looked at Gippeto's tutorial,i thought i could get more pressure from a fridge compressor,and the hill pump a lot more,i can get a fridge compessor for about $20ozzy.The hill is quite a bit more $289,so after a couple of hundred hours reading spudfiles,i think thats the way i'll go.I;d really like to experiment with high pressure,maybe i can ask wiz about his hills pump,and how it performs.Thankyou very much for your help Jackssmirkingrevenge.You are truly a great asset to spudfiles.May i add for the spudders here in australia,sodastream bottles are $18 at woolworths(full)and are 250 bar rated.I also found stainless steel 40bar qev's at a company called sealexel(india)i am waiting for a reply (i may have to buy bulk).Also i'm looking for a regulator for a sodastream,palmers pursuit only have fittings for american sodastream,i think my thread is bsp(.820)thankyou.
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Unread postAuthor: Filippo.san » Fri Jun 14, 2013 9:09 am

Dear jpalf1, I use a rubber disk with a tiny hole to slow the flow from the chamber, so that I don't use all the air. It takes about six or seven seconds to refill the qev.

Jack said the weakest part of my gun is the blowgun. Does anybody know of a stronger sobstitute of my blowgun?
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Unread postAuthor: jpalf1 » Fri Jun 14, 2013 10:33 am

Thanks Filippo.san,i'll do some experimenting.I haven't tried but maybe a slide valve like Jackssmirkingrevenge suggested,palmers pursuit have some that can hold a fair amount of pressure.What about a mechanical valve,like a qev but with a button for a trigger,some work when you press the button or trigger,the other type work when you release it.I'm looking for one now,i just don't want to get the 2nd type.It's in spudfiles-somewhere.
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Unread postAuthor: jackssmirkingrevenge » Fri Jun 14, 2013 10:37 am

Filippo.san wrote:Jack said the weakest part of my gun is the blowgun. Does anybody know of a stronger sobstitute of my blowgun?


As suggested earlier, a ball valve is a good substitute.
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Re:

Unread postAuthor: ham_machine » Sun Sep 28, 2014 6:52 am

jpalf1 wrote:I also found stainless steel 40bar qev's at a company called sealexel(india)i am waiting for a reply (i may have to buy bulk)


Hey, did they ever reply to you? Did you buy any off them? I have been toying with the idea of using one of those cheap ebay QEV'S, but I would much rather buy a quality product with the correct pressure rating for what I need.
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