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Can sprikler valves be used on semi auto?

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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Can sprikler valves be used on semi auto?

Unread postAuthor: Kai » Thu Jun 04, 2009 7:08 pm

I am pursuing a dream to have a semi auto tennis ball gun, my first question, is, what diameter pvc fits tennis balls? Then, If i put a sprinkler valve in front of my air compressor, will it automatically re-seal and re-pressurize? Yes, i want something like the cannon on rob dyradek's fantasy factory.
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Unread postAuthor: Technician1002 » Thu Jun 04, 2009 7:29 pm

One step at a time.. 160 or 180 PSI 2.5 inch PVC fits tennis balls just fine. Not all 2.5 inch PVC has the same inside diameter. The sched of a pipe defines the wall thickness so Sched 80 and 40 both have the same OD, the inside diameter is not the same. You would have to work very hard to get a tennis ball in a 2.5 inch sched 80 barrel.

Sprinkler valve, yes they can be used to open and close. It will work. Now the part you won't like. The math.. Let's say you are using a 1/4 inch pipe from the compressor and blowing air at 1,000 mph through it. Sounds good untill you have to fill the volume of the 2.5 inch barrel. As you double the diameter the area increases 4X and if the high speed air didn't expand it would travel at 1/4 the speed.

Now the part you won't like.. the ball will eject much like a car in a auto shop goes up on a lift.

To fix that, most spud guns use a local storage tank right on the gun and use a high volume fast valve in between so the pressure in the tank can dump into the barrel very quickly. For a 2.5 inch barrel, you will want a valve at least an inch in size.
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Unread postAuthor: cannon monkey » Thu Jun 04, 2009 7:32 pm

ok umm for what i know tennis balls go in 2 and a half inch pcv sch 40
i pretty sure...
if you make a normal cannon... with a chamber and find the clip for bike pumps so it stays or use quick connnets it will re-fill and grow more pressure
if u mod the valve with a blow gun give it 2 secs with the blow gun closed it will re-seal any other questions?
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Unread postAuthor: Kai » Thu Jun 04, 2009 8:04 pm

I do have a modded 3/4" sprinkler valve w/ a blowgun valve on it but i can just move the blowgun to a larger diameter valve like a 1" or bigger if i can find one.


Here's a crude diagram, its not my final practical design but theoretically, will it work?

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Unread postAuthor: Kai » Thu Jun 04, 2009 8:39 pm

hey, con you think of any other type of ball that is cheap and easy to find like tennis balls, but is non lethal unlike golf balls


PS: forgive the double post
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Unread postAuthor: cannon monkey » Thu Jun 04, 2009 8:41 pm

..like get smaller barrel half inch 3/4 or 1 inch and use bouncey balls :D their wat 10 for a dollar?
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Unread postAuthor: Kai » Thu Jun 04, 2009 8:56 pm

nahhh, any other ball ideas?anything that can go into a 1" or 2" pipe?


PS: i was amost done w/ a pneumatic sprinkler valve marble gun, i may just make that semi auto
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Unread postAuthor: cannon monkey » Thu Jun 04, 2009 8:59 pm

paintballs... their pretty cheap 500 for 13-20 dollars
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Unread postAuthor: Kai » Thu Jun 04, 2009 9:04 pm

nahhhhh... hey, wht about raquet balls, i think more expensive but, easy barrel diameter, don't want to have to look all around for 2.5", unless it's easy to find, do they have 2.5" at lowes or home depot, im not really sure.
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Unread postAuthor: cannon monkey » Thu Jun 04, 2009 9:06 pm

they dont have 2.5 at homedepot or lowes.... and i bought raquet balls before ( their blue right all rubber no fur? ) if so they dont fit in 2 inch...
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Unread postAuthor: Kai » Thu Jun 04, 2009 9:17 pm

right, but they come in a few different colors, blue, green red, orange. ,but yea, did they fit?
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Unread postAuthor: cannon monkey » Thu Jun 04, 2009 9:24 pm

i had blue and no they didnt fit i only saw blue....
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Unread postAuthor: Gaderelguitarist » Thu Jun 04, 2009 9:36 pm

2.5" PVC can only be found at home depot or lowes in the form of grey electrical conduit. It's fine for combustions, but I'd hesitate to use it on a pneumatic where higher pressures are involved.

As for your semi-auto plans, good luck. Unless you have a spring fed mag with a detent, you'll want to build a blow-forward bolt loader; something that is out of the reach of the beginning spudder (I'm only assuming you are).


Next, flow will be the biggest restriction for you. Tech wasn't joking around.
Look into building a secondary tank that would more quickly fuill up your primary firing tank.
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Unread postAuthor: gunzz » Fri Jun 05, 2009 12:01 am

well i think a bolt action design would improve that alot. also 2.5 inch conduit should be fine for a barrel but not a tank. i mean, when have you guys ever heard of a pneumatic barrel explosion! but to use it for a tank would be bad.
so as long as no air is actually STORED it should be fine i think.
no higher barrel pressure than a combustion really.
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Unread postAuthor: Gaderelguitarist » Fri Jun 05, 2009 12:12 am

Always better to be on the safer side considering PVC shatters rather than tears. A failure would be devastating.
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