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qev question

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 question

Unread postAuthor: grock » Tue Jan 05, 2010 6:46 pm

i know that QEVs are commercial optimized piston valves, but my question is how much flow do they have? will a 3/4" QEV provide enough flow to fully use the volume of a 3/4" barrel? or should i go for a 1" QEV on a 3/4" barrel
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Unread postAuthor: Lockednloaded » Tue Jan 05, 2010 7:05 pm

a bigger valve can always increase flow in my experience, but have you looked at the huge jump in price from 3/4" to 1" its a good 70$ wasted if you ask me. If you've got money to blow go for the bigger valve, but few spudders do so i'd go 3/4"
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Unread postAuthor: MrCrowley » Tue Jan 05, 2010 8:29 pm

Stay with the 3/4" QEV, most spudders will jump to piston valves afer 3/4". Far cheaper and you can control such factors like flow and operating pressure.
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Unread postAuthor: grock » Wed Jan 06, 2010 2:36 am

i get what you guys are saying about the price, but if the surface area of 3/4" PVC is ~.53 square inches, does a 3/4" qev have more flow than that? because it seems like a waste to have a valve with more flow than the barrel would allow
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Unread postAuthor: jackssmirkingrevenge » Wed Jan 06, 2010 3:04 am

grock wrote:i get what you guys are saying about the price, but if the surface area of 3/4" PVC is ~.53 square inches, does a 3/4" qev have more flow than that? because it seems like a waste to have a valve with more flow than the barrel would allow


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I would say the flow would be equivalent to the barrel.
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Unread postAuthor: jeepkahn » Wed Jan 06, 2010 10:19 am

Slightly off topic, but in a highpressure mini(JSR) you can put a plug in "sw" and the gev becomes a mini coax chamber...
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Unread postAuthor: POLAND_SPUD » Wed Jan 06, 2010 10:38 am

well yeah but you can also feed air via SW2 and put a spring behind the piston to build JSR's farting machine :wink:
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Unread postAuthor: jackssmirkingrevenge » Wed Jan 06, 2010 11:07 am

POLAND_SPUD wrote:JSR's farting machine :wink:


You spend years of R&D perfecting the contant flow full auto valve, and all they remember is the farting machine *sigh* :D
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Unread postAuthor: jeepkahn » Wed Jan 06, 2010 11:16 am

jackssmirkingrevenge wrote:
POLAND_SPUD wrote:JSR's farting machine :wink:


You spend years of R&D perfecting the contant flow full auto valve, and all they remember is the farting machine *sigh* :D


And Fullstop or Not, A certain mod will ALWAYS be MCCrowley... :headbang:
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Unread postAuthor: Technician1002 » Sat Jan 09, 2010 10:27 pm

grock wrote:i get what you guys are saying about the price, but if the surface area of 3/4" PVC is ~.53 square inches, does a 3/4" qev have more flow than that? because it seems like a waste to have a valve with more flow than the barrel would allow


I used to think that until I started playing with bigger stuff. In an air cannon the high speed flow is in the area of the valve. The lower the turbulance, the higher the flow.

Using a valve at twice the recommended size means the flow velocity is half for the same flow voulume. This drops the loss in the valve to 1/4 due to turbulance. Believe it or not, slow flow through the valve is a good thing as long as it is high volume. Let the gas enter the barrel under full chamber pressure and expand where it does the most good. The higher the force on the projectile the better. :D
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Unread postAuthor: Marffy » Sun Jan 10, 2010 11:00 pm

i cant really answer your question but if i were to guess i'd say that a 3/4 QEV could use the full volume of a 3/4 inch barrel

offtopicish:it seems alot of ppl are not even answering the question, they just give advice on a valve you should choose. i agree tho either get a 3/4 QEV or if you want more power get a small home made piston (1")
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