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QEV questions...

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: Lockednloaded » Wed Jun 30, 2010 10:10 pm

what kind of pressures are we talking about, would 300psi unsupported be fine? its some pretty thick metal so if there is no noticeable difference i don't want to risk my valve or my drill bits.

noticeable difference in sound when fired

what kind of sound, mine is nearly silent ATM[/code]
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Unread postAuthor: c11man » Wed Jun 30, 2010 10:37 pm

i dont thing a nylon washer on the back would be enough, i would put a bolt through with washers on both sides. there is no need for epoxy if you make the hole through the piston small enough the rubber will seal around the bolt on its own. with a nut on the back of the piston the supports of the back section will also need to be removed to make room. with metal washers i would take it up to 600psi but thats just me
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Unread postAuthor: MrCrowley » Wed Jun 30, 2010 10:54 pm

what kind of sound, mine is nearly silent ATM

I actually thought it made less noise after the mod than before removing the supports.
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Unread postAuthor: Lockednloaded » Wed Jun 30, 2010 11:06 pm

I was hoping for a high pitched noise, I've been trying to make this gun make a whizzing noise be adding different breaks on the end. as of now the barrel is 6 feet, so the only loud nois is the projectile making contact with a target
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Unread postAuthor: jhalek90 » Thu Jul 01, 2010 10:47 am

Best "Loud high pitched noise" making muzzle break i have found is simply sticking a cross fitting on the end of the barrel.

Works pretty good on all my guns.
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jackssmirkingrevenge wrote:I wonder... if you put flammable vapours inside a lady... could you get her to diesel?

POLAND_SPUD wrote:Anything is possible with the proper 3-way valve.
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Unread postAuthor: velocity3x » Thu Jul 01, 2010 11:22 am

Lockednloaded wrote:I've been trying to make this gun make a whizzing noise


Usually, I require at least 3 bottles of beer. :lol:
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Unread postAuthor: jhalek90 » Sun Jul 04, 2010 9:29 pm

Oh, and here is somthing to think about...
What is the ID of your barrel?

Those supports are only going to limit performance if the holes in the port of your QEV have a greater surface area than the ID of your barrel.

to summarize:

if barrel ID < QEV exhaust ID then{Barrel id =limiting factor}

just make sure to take the surface area of the "sticks" in the qev port into account when finding the exhaust port ID.

EDIT: i would Guess by looking at your photo, that the ports are roughly 33% blocked.

So, if your barrel is any more than 66% of the size of your ports.... then try removing them,... otherwise don't bother.
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jackssmirkingrevenge wrote:I wonder... if you put flammable vapours inside a lady... could you get her to diesel?

POLAND_SPUD wrote:Anything is possible with the proper 3-way valve.
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Unread postAuthor: ramses » Mon Jul 05, 2010 6:11 pm

note that that is cross sectional area, NOT diameter.

The supports also probably create significant turbulence.
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Unread postAuthor: Technician1002 » Mon Jul 05, 2010 6:23 pm

Please note that one large round port will flow better than 2 smaller round ports with the same total cross sectional area. The single port has Less wall surface area for friction. The double port has turbulence of joining two streams.

There is more to the fluid dynamics than total port cross sectional area. This is why I used a total port area of 6 sq in to feed the outlet of ny 3 port 2 inch valve. The valve outlet is only 3.14 sq in.

In rhe QEV, you want more port sq in than the outlet pipe size to keep the flow loss to a minimum in the ports.

Just matching the area will leave some losses in the valve.
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