If you want something for the projectile that isn't inherently lethal, chamber the barrel for a standard baseball or softball. They're heavy enough to fall out the backside of a tree, and can be easily drilled through at a shallow angle to attach a string.
Don't think you need any metering, just hammer the firing handle of the extinguisher with the heel of your hand to give a short burst.
And for smaller trees, you can just wind up and toss it the old-fashioned way.
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The Austrians gave Napoleon a fair ration of shit as they had a number of marksmen groups armed with air rifles. No cloud of smoke to mark their positions, deadly accurate, powerful and repeaters
Gunner
"Liberalism is a philosophy of consolation for Western civilization as it commits suicide"
- James Burnham
It's a matter of peak pressure, metering time, such flowrate throttling as may be present and barrel length. Acceleration continues as long as instant_pressure > friction.
You're starting to scare me a little. It is not safe to put compressed air of over (about) 1000 psi in a CO2 tank.
Here's a peek at the gun that I made
I'll skip #1, it's obvious. You want really fast
2) Your valve size is the smallest opening between your air chamber and your projectile. Make it as big as you can. For low pressure, they are often an inch or larger. Mine is .5" 3) Co2 is stored as a liquid. That's why you get so many shots (paintball) from a small container. You MUST have an air chamber that allows the CO2 to become a gas, or you're going to blow through your CO2 supply pretty quick. The volume of your air chamber ensures you have a supply of air waiting to be used by your valve. The higher pressure that you use, the smaller your chamber can be. For low pressure spud type guns (around 100 psi or less) they recommend a chamber equal in volume to your barrel as a starting point.The gun shown in my picture uses CO2, or compressed air at about 800 psi. The expansion chamber is only about 3" long, and .562" in diameter. The valve was designed just for this gun. I get about 2 shots per ounce of CO2, but prefer compressed air for rapid shots.
Remember, most people use PVC for spud guns, even for their pressure chamber. It's really not safe.
To get answers to all your questions, check out
The cold probably makes the PVC brittle. The air system I use pressurizes the outer chamber to shop air pressure, and firing releases the pressure.
I made one from PVC for my prototype. It was only operating at about 75 psi. I installed a pop off valve to insure I didn't over pressurize. It was built to shoot tanks in paintball games. I just kept picturing what would happen if I tripped and landed on it. Even without pressure in it, I'm sure I would break it. With pressure, it was just scary. That gun no longer exists.
I didn't suggest that. But I suspect it would be okay as the extinguishers have a test pressure of 222 bar (over 3200 psi).
Best wishes,
Chris
Thanks, Dan. Well I bought a pair of extinguishers yesterday, so the project has begun. I've also just seen really heavy surveying tripod for sale and I'm seriously tempted by that!
Best wishes,
Chris
To clarify, I'd think that 1000 psi is towards the upper end of what's reasonable. I can't see that it makes any difference whether the cylinder is filled with carbon dioxide or air.
Chris
Except that you'll get more shots from CO2.
CO2 will stay relatively at the same pressure for every shot until the liquid is gone. HPA (high pressure air) will give you less velocity for each shot until your tank is empty. Unless you use a paintball tank. They have built in regulators. Most produce about 800 psi at the outlet.
Dan, what kind of hose did you use to connect the extinguisher to your barrel? Did you use a hydraulic hose, some kind of special hose for carbon dioxide, or the original hose which came with the extinguisher?
I want to do it right, but I don't want to spend money unnecessarily.
Best wishes,
Chris
Grease whips are cheap and high pressure rated, though they will sometimes blow bubbles in the skin when abused a bit too much.
Check out ebay or the local paintball store for paintball hoses.
Cheers Trevor Jones
I need a 1/4" bore hose. I suspect grease whips and paintball hoses are more like 1/8" bore.
Chris
Yea, they're very small.
Have you looked at McMaster Carr?
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