"Don Foreman" wrote in message
...
On Mon, 24 Apr 2006 14:23:17 GMT, "Dave Lyon"
wrote:

What specifically are you trying to accomplish?

I've built a CO2 powered gun for use against paintball tanks. It fires a
foam projectile that I also build at 250 fps. It could easily be designed
to
shoot much harder.

I ran into 2 tricky areas. The first one was making a projectile that
wouldn't hurt somebody. The 2nd was getting O-rings that could handle the
800 + psi of CO2.

Let me know if you'd like to see some pictures of my gun. If you want, I
can
help you design one to meet your criteria.
"Gunner" wrote in message
.. .

I'd like to see that too. I'm specifically interested in the valving
mechanism you used. I have a need to shoot maybe a dozen golfballs
to break up some squirrel nests, and I have a 20-lb bottle of CO2.
250 fps would be more than I need. 100 ft/sec would get me about
150 ft of height, which should be ample since the squirrel nests are
about 40 feet up. That'd keep things at a pretty safe 20 joules.

A slingshot doesn't quite cut it. I need a large enough projectile
to break up those nests, not just punch holes in them.

I didn't know how to use (or where it is) the board that you guys have for
pictures, so I sent some to Don. Hopefully he'll be kind enough to post
them.
I included a crude iges file that I used to machine it from. Please don't
assume this is a safe design. I am not an engineer, and we're dealing with
some very high pressures.

The gun shown operates from CO2. At room temperature, it is somewhere
around 800 psi. The black hose connects to a standard CO2 tank used for
paintball. They hold about 20 ozs, and can be worn on your back

In the iges file, you can see on the left side of the plan view a large
drilled hole (I think it was around .687) This is used as a reservoir to
hold the CO2 ready for the next shot. With a bit of studying, you should be
able to see the valve. It is held up to seal against the top by a spring.
The valve has a very small air passage that allows the CO2 to bleed by it so
the pressure is the same on both sides of the valve. There is a seal on the
bottom side of the valve that is held in place by some bellville springs, a
ball bearing, and the shape of the trigger. When the trigger is pulled, the
air underneath the valve is allowed to escape very quickly. The spring can
no longer hold the pressure that is above the valve, so it moves down
allowing the gas to escape from the passageway leading to the barrel.