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Help Making A QEV - English

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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Unread postAuthor: max76 » Sun Jan 08, 2012 4:46 am

all finished or.
I have a problem but I get the air.
the piston stop fitting well.
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 08, 2012 4:48 am

What's your first language? Maybe someone on the forum is from the same country or speaks the same language and can help you express yourself better ;)
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Unread postAuthor: max76 » Sun Jan 08, 2012 4:51 am

What can I use as a sealin gasket for the piston?
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 08, 2012 4:52 am

Car tire inner tube or any similar rubber sheet.
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Unread postAuthor: jrrdw » Tue Jan 10, 2012 4:46 pm

Bump!
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When life gives you lemons...throw them back they suck!
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Unread postAuthor: evanmcorleytv » Tue Jan 10, 2012 4:53 pm

wait.. Why did I become author of this post? haha

edit: OH. I see why!! Thanks!! I feel useful!!
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Last edited by evanmcorleytv on Tue Jan 10, 2012 4:56 pm, edited 1 time in total.

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Unread postAuthor: jackssmirkingrevenge » Tue Jan 10, 2012 4:55 pm

Thanks for splitting it and not deleting it, I know that it appears rude on an English speaking forum to communicate extensively in another language but I can assure the members of the board that it was all spud-related and the information presented is all relevant to the question :)
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Unread postAuthor: jrrdw » Tue Jan 10, 2012 4:58 pm

evanmcorleytv wrote:wait.. Why did I become author of this post? haha


It's where the split happened.

The true author is listed in the other thread http://www.spudfiles.com/forums/help-making-a-qev-italian-t23740.html

"max76"
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Unread postAuthor: evanmcorleytv » Tue Jan 10, 2012 5:45 pm

IS THIS A STICKY WORTHY THREAD? I THINK maybe.
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Unread postAuthor: jrrdw » Tue Jan 10, 2012 5:53 pm

evanmcorleytv wrote:IS THIS A STICKY WORTHY THREAD? I THINK maybe.


NO! Never ask for a "sticky", it's not even your thread. :roll:
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Unread postAuthor: evanmcorleytv » Tue Jan 10, 2012 5:55 pm

jrrdw wrote:
evanmcorleytv wrote:IS THIS A STICKY WORTHY THREAD? I THINK maybe.


NO! Never ask for a "sticky", it's not even your thread. :roll:


I know.. well.. now I'm sad..
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Unread postAuthor: josephlys » Thu Jan 19, 2012 11:09 am

Do piston valves leak often, and if so what would be the main cause/concern the front of the piston/gasket head?. Btw awesome post and superb contribution. Learned a lot, thanks.
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Unread postAuthor: Technician1002 » Thu Jan 19, 2012 12:18 pm

Piston valves are an achievement to get to work right. Common issues are the inability to get the valve closed and not leaking so the chamber can be filled with air and too much leaking past the piston when the pilot is operated so air blows out the pilot instead of opening the valve.

The third common issue is with the bumper. Piston valves open with lots of energy which tends to break things.

It takes a fair amount of skill to make a working piston valve.

When they do work, they are worth the effort as it is one of the highest performing air cannon valves possible.

I edited a prior photo to show a recommended change. For best flow and quick operation, an open piston valve should be centered in the T. If the valve seat is at the end of the T the flow is restricted when the valve starts to open. If the seat extends into the T about 1/3 the way in, then air has free flow to the valve opening. When the valve piston has moved open to the other side this places the gap between the piston and seat in the large diameter portion of the T for good flow.
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 19, 2012 12:35 pm

Technician1002 wrote:I edited a prior photo to show a recommended change. For best flow and quick operation, an open piston valve should be centered in the T. If the valve seat is at the end of the T the flow is restricted when the valve starts to open. If the seat extends into the T about 1/3 the way in, then air has free flow to the valve opening. When the valve piston has moved open to the other side this places the gap between the piston and seat in the large diameter portion of the T for good flow.


I had actually realised this error and posted a similarly modified diagram elsewhere, but when it came to this thread I could only find the original :)
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Unread postAuthor: josephlys » Thu Jan 19, 2012 1:02 pm

Does the piston have to act as a divider to separate the high pressure air at the pilot end and the main air-chamber? Or is it sufficient that the piston's front part properly seals the valve?
Or is it a good idea to make/use a longer piston. Say I don't use a spring and I'm not pumping from the air-chamber.
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