Friday, 18 October 2013

Air cannon

My title is sadly lacking in pazazz, but it aptly describes what this post is all about: My (right now at least) only pneumatic projectile firing device. First, a cupple of pics:

As you can see, it was constructed from two discarded propane bottles that have had their valves unscrewed, leaving a standard 3/4 in NPT threaded female fitting. These are screwed into custom manifold made from PVC pipe and fittings that leads to an 1/4in "M" type quick connect for connection to a compressor, and to a modified 1in sprinkler valve. The valve was modified by removing the electrical selonoid, filling the hole it screwed into with epoxy, and drilling a hole in the centre of the device, threading in a 3/8 to 1/4" metal bushing ( I orriginally had just the 1/4" fitting coming off the hose, but stress on it caused it to move a bit and leak), and finally threading in a coiled hose that leads to either a blow gun or (as I have right now due to lack of parts) a simple ball valve. When the blow gun (or ball valve) is opened, preasure on one side of the diaphram in the sprinkler valve is released causing the diaphram to open and lots of air to rush by. After the valve is an adapter that goes from the 1" female output of the valve, thru a cleanout tee and to a 2" male threaded fitting. I have another large combustion launcher that uses a 2" male threaded output, so with this I can use the same barrels on both of the cannons. The pictures are with my (rather pitiful) 1.5 in barrel, but I also have a short 4" one (you can see that one in the pics too), a 10 foot 2" one, a 20 foot 1" one, and an 8 foot 1/2" one. even with the inch and a halfer you see on there, I managed to put rocks and 1/2" pvc thru a large metal can, split a 1 foot long 2x6 piece of wood with a rock and break into multipul pieces a 2.5 inch thick paving stone using a metal pipe nipple.
I also once shot an unfrozen paintball thru a piece of 1/2 in thick wonder board using that 20' long barrel I mentioned.( for those of you who do not know, wonderboard is pretty much drywall, except made from cement.) Anyway, you get the picture, pretty powerful device, and lots of fun. Two last things before I go, one, if you are going to experiment with potato cannons etc, please wear, at the bare minimum, safety glasses, and do not use sun faded/scored/cracked or un pressure tested pipe, and two, NEVER, ever point these at anything living, or that has a chance of ricocheting back into you. I know, I hate dire warnings too, but you are dealing with stuff that WILL kill you given the chance.

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