3" Barrel Sealing Piston Valve

[tony48]

This is my first real spud gun (not counting a hairspray combustion and a ball valve pneumatic) and I spent alot of time planning and making it. I really wanted to make it nice and clean but still be able to fully access the piston as well as change barrels and chambers. Comments and suggestions are welcome and appreciated. Alot of credit needs to be given to Technician1002, Gun Freak, Lockednloaded, and Crna Legija for their help when I asked questions in the forum.

Specifications
Chamber- 40" of 3" PVC (removable)
Valve- 3" Piston
Trigger valve- 3/4" Ball Valve
Porting- 2" PVC with 2" female threads to connect to barrel
Fill valve - 1/4" ball with Quick Connect
Barrel- Interchangable from 1/2" to 3"


Here's an overview of the gun without a barrel on it.


Piston
It is a 2.5" coupler turned down on a lathe to fit perfectly. the end disks are made out of sheet pvc that was turned down to slide snugly into the coupler. a small piece of 2.5" pipe is glued inside of the coupler for support. The sealing face is 1/8" rubber from Mcmaster. A thin sheet of foam is behind the sealing face to allow the sealing face to flex to match the 2" pipe. The whole piston and half a tennis ball (bumper) is held together with 1/4" all thread.



Piston in back of valve


Fill Valve/Exhaust Valve
My fill valve is a 1/4" ball valve with a quick connect fitting. The exhaust valve is a 3/4" ball valve. This was the best way I could configure the exhaust valve, fill valve, and gauge. The O-ring groove to seal the back of the piston valve was cut on a lathe. The 8 holes for the retaining screws were drilled on a drill press and then tapped. I hand twisted a countersink bit in the holes on the inside of the 3" coupling to smooth them out and keep the o-ring from getting chewed up when taken out and put in. It seals perfectly and is very easy to take out and put in. The black foam inside of the 3" to 2" bushing is another bumper.




The barrel supports are made from 2x4's and are custom made for each size barrel. Below are barrel supports for 1", 2", and 3/4" barrels.

Barrel support with 1" barrel


Gun overview with 1" barrel


Size reference picture. I am 6'3" tall.


No damage pics yet but they should be up within a week or so. Let me know what you all think. Any questions or picture requests gladly accepted. This gun is a beast and with it's tight piston tolerances can open with as little as 3 psi. I'm really excited that it works so well and can't wait to do some damage with it.

[Technician1002]

Nice. That will be a beast to fire.

[Lockednloaded]

You really shouldn't use a barrel smaller then 1-1/2" otherwise you'll be choking flow and wasting air. I'd recommend a smaller porting launcher for your smaller barrels. Congrats on getting it working, you'll certainly be happy with the two inch barrel, I'm glad I could be helpful to you

[tony48]

You really shouldn't use a barrel smaller then 1-1/2" otherwise you'll be choking flow and wasting air. I'd recommend a smaller porting launcher for your smaller barrels. Congrats on getting it working, you'll certainly be happy with the two inch barrel, I'm glad I could be helpful to you

Yeah, oh well. The smaller barrels are just for fun and testing the cannon out. I'm currently working on a smaller launcher so I can have fun firing smaller things. I'll have plenty of fun with all of the barrels, especially the 3" which wine bottles fit perfectly in

[Gun Freak]

Glad I could help, it looks amazing. You did a really good job on it. It is very clean. The chamber is way overkill for barrels under 1.5" but who gives a damn! I personally would have gone with a sprinkler valve pilot for better accuracy and easier triggering, but who needs accuracy on a spudgun, right? Anyway, it looks awesome. :thumbright:

[tony48]

Glad I could help, it looks amazing. You did a really good job on it. It is very clean. The chamber is way overkill for barrels under 1.5" but who gives a damn! I personally would have gone with a sprinkler valve pilot for better accuracy and easier triggering, but who needs accuracy on a spudgun, right? Anyway, it looks awesome. :thumbright:

Yeah I made the chamber so it would be large enough for a 5' 2.5" barrel. I'm looking to get a 3/4" sprinkler valve for the pilot for the reasons you listed but just started with the ball valve to make sure everything worked alright. I'm glad you like it and I'm very impressed with it also!

[mark.f]

Great job swirlface.

In other news, nice cannon, although you did have me rather excited with the title (3" piston valve), thinking it was based in a 4" tee with 3" porting...