Best 3/4 Bore Cannon Possible

[BeaverRat]

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

[Mr.Sandman]

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!

[jackssmirkingrevenge]

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.

[Crna Legija]

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

[velocity3x]

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.

[jackssmirkingrevenge]

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

[c11man]

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

[BeaverRat]

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?

[Technician1002]

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.

[clemsonguy1125]

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

[BeaverRat]

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?

[clemsonguy1125]

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

[BeaverRat]

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

[clemsonguy1125]

Yes, as long as your pistons not to long

[BeaverRat]

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