SpudFiles

Hello,
I have a couple questions for you guys here... I will be making a cannon with a 3/4 inch barrel, and a 2 inch chamber. I am wondering what the best possible valve power-wise for this would be. I am mainly going for pure performace here - I don't really care about efficency, so I will be using a 2:1 C:B Ratio.

Here are some ideas I had

-1 inch modded sprinkler valve (too expensive to go bigger)
-3/4 inch QEV
-Barrel sealing piston valve (what size tee should I use with 3/4 valve seat?)

Thanks

The Qev and piston valve will be your best choices. But if you have the right tools, you can make the piston valve more effective and stronger.
A qev is basically a commercial piston valve with a thin rubber diaphragm. In my opinion, you should make it yourself, nothing beats the satisfaction of something you make working!

BeaverRat wrote:I am wondering what the best possible valve power-wise for this would be. I am mainly going for pure performace here

Well, the best possible valve is not to have one, but this limits your choice of projectiles. A burst disk valve offers performance that is practically just as good and allows freedom of choice in terms of projectiles, though it's a bit more involved when it comes to reloading.

if you do build your own piston valve use 1'' tee

BeaverRat wrote: I don't really care about efficency, so I will be using a 2:1 C:B Ratio.

I found out the hard way that building pneumatics with a C:B larger than 1:1 is the wrong thing to do but...... that's just my opinion.

velocity3x wrote:I found out the hard way that building pneumatics with a C:B larger than 1:1 is the wrong thing to do but...... that's just my opinion.

Not everyone runs at the same pressures you tend to though

velocity3x wrote:

BeaverRat wrote: I don't really care about efficency, so I will be using a 2:1 C:B Ratio.

I found out the hard way that building pneumatics with a C:B larger than 1:1 is the wrong thing to do but...... that's just my opinion.

its not rare for some of my launchers to exceed 3:1 ratio with some barrels. high C:B ratios is not a problem unless the volume and pressure of gas is very high as in your creations

Oh, I forgot to mention, it will run at roughly 150 PSI. I think I will go with a piston valve actuated by a modded sprinkler valve.

With the barrel porting of 3/4th inch, will a 1 inch tee be the propper ratio, or do I want to go with maybe a 1.25 inch tee?

Also, anyone have any ideas for a nice piston for a 1 inch tee?

You do want a large CB ratio for low pressure low force launches. I have not posted much about it here due to being busy shooting and a large (100+) gathering. Launching eggs with a small chamber and high pressure breaks them. A long barrel, low pressure, and high flow can get some fantastic ranges with raw eggs. This was a hit at a local egg drop engineering contest. We threw eggs over the building and landed them on the roof of the building on the other side of the parking lot. I wish we had video of the shots, but we don't.

In the 3 gallon launcher with a 2.5 inch barrel and foam sabot, the max an egg will take is about 15 PSI without breaking. Around 20, they pretty much all break.

BeaverRat wrote:Oh, I forgot to mention, it will run at roughly 150 PSI. I think I will go with a piston valve actuated by a modded sprinkler valve.

With the barrel porting of 3/4th inch, will a 1 inch tee be the propper ratio, or do I want to go with maybe a 1.25 inch tee?

Also, anyone have any ideas for a nice piston for a 1 inch tee?

What material are you using for your gun,pvc, if so Id stay below 120 PSI, I used a 1 inch yee for my 3/4 porter and the piston was a 1/2 Inch CPVC coupler wrapper in tape and filled with hot glue, washers were epoxied to both end and a toy "popper was epoxied to one washer. A ty popper is like a rubber bowl that you invert and set on a table, they then pop into the air

Why did you fill it with epoxy? It seams to me that would add unecissary weight which would slow down opening times... Isn't a 1/2 inch coupler strong enough?

I actually filled it with hot glue, it was mainly because I was afraid it would shatter at higher pressures(100 psi)

Ok, I actually decided to use a 1/2 PVC coupling. It's a really close fit, so I will just sand it down a bit... If I set the 3/4th inch porting at the dead center of the tee, will that give enough flow?

Thanks

Yes, as long as your pistons not to long

why would it matter how long the piston is? I can set the piston travel pipe at whatever length i want...