Understanding piston valve

[The Boomstick]

Hello, I'm new to the idea of coaxial/piston valves, though I do have previous experience with other pneumatic cannons (3 previous ball valves, various sizes), and some basic combustion cannons.

I have read many of the posts and watched the tutorial on the building of the piston valve.

I have the plans for my new coaxial piston valve gun drawn out. If anyone would look at them and point out any errors, or make any tips for improvement, it would be appreciated. I plan on shopping for parts in a couple days.



*I realize I forgot to draw in the pressure gauge, don't worry, I'm know its necessary*

[Benny]

nothing seems wrong, and you dont need a pressure guage, unless you are filling from something that doesnt have a pressure guage.( bike pump, ect)

[Atlantis]

http://forums.spudtech.com/topic.asp?TOPIC_ID=13265

That site explains it very well. Hope that's what you were looking for.

[)DEMON(]

You must remember to have a small hole in your piston so air can fill the chamber as well.

[sgort87]

You don't need an equalization hole all the time. If air can leak around the piston then you are fine.

[djt]

ive got an idea. make the piston piston fit perfectly and seal in the chamber. then drill a small equilization hole on one side of the piston. on the side of the piston that seals the barrell put a little rubber flap over the equilization hole to act as a sort of check valve. that way when you open the valve to make the piston slide back, all of the air will go out the barrell and none can come back through the hole in the piston.

[The Boomstick]

Thanks to everyone who posted.

With an estimate of 120-ish cubic inches, is that a tolerable size to go with a hand pump. I planned on stylizing one to attach to the cannon. If it is too large, should i consider co2 or just simply downsizing the chamber slightly?


Going parts shopping tonight or wednesday.

[SpudStuff]

yes you can use a hand pump for that size. it may take a while but you can use it.

[noname]

You're going to be pumping for quite a while. My pump can pump about 15 ci each pump and my coax is ~92 ci. It takes about 15 pumps to get it to 55 psi. With a hand pump you'll probably be pumping half that much air, so it would take ~40-45 pumps to get to 55 psi with yours. Have fun getting huge triceps.