Coaxial (kinda) Cannon

[kablooie]

This is my version of PVC Arsenal 17's Fish Killer 2 (http://www.spudfiles.com/forums/fish-ki ... 11714.html). I was looking for something different to do and this ingenious design caught my eye, although it occurs to me that I didn't ask PVC Arsenal 17 for his permission, so I hope it's okay.

Anyway, I took his design and scaled it up to 3/4" barrel and a 2" by 1.25" chamber. The barrel is five feet long and the chamber is about three feet long. The barrel slides through the inner 1.25" pipe of the chamber, but I won't go into detail on this because it is explained in the Fish Killer 2 topic. The main changes I made were:
-I used the Bolt action breech found on this website
-I used a 1" modded sprinkler valve piloted by a cheap home depot blowgun and a ball-valve safety
- I moved the trigger forward using a very simple triggering mechanism that allowed me to reduce the pilot volume drastically (Thanks to JSR for this idea).
-It's a lot bigger (and pretty heavy)
So far it is powerful but not hugely so, probably because of all the restrictive 1" pipe I used to accommodate the breech loader. The other flaw is that I did a poor job of controlling the primer (next time I will probably use the clear stuff). I have not painted it because I do not want our neighbors to think I am carrying an bazooka or something around, so any suggestions for non-intimidating color choices are welcome. I am also afraid that because of all the 90 degree elbows and 1" pipe that is so restrictive that part is liable to blow up, and I stick my arm through the opening in between them, placing the pipe that could explode right over my heart and by my face. Oh joy. Now for some pics:

[potatoflinger]

Wow, you've got a very nice collection there!

[ALIHISGREAT]

nice cannons, and JSR will be pleased someone finally put his trigger idea into practice (although you may have come up with it independantly?)

[kablooie]

Thanks, I make one of these over every long vacation form school, best entertainment around. And I did get the trigger method from JSR. Do either of you have any thoughts on whether or not it's safe to use? I have heard bad things about that much restriction leading to a failure.

[potatoflinger]

I don't think you would have any trouble, since you used primer and cement. (though you may want to check with some more experienced spudders)

[ALIHISGREAT]

restriction??? are you talking about the 1/2" cannon? it should be alright

[daberno123]

As long as you have used all NSF-pw parts (which i think u have), it should be safe to use. Actually, as long as they are properly glued, the fittings are actually stronger than the pipe because they are double layered

[kablooie]

Okay then, thanks for the help. It is all glued very well (no leaks) although the chamber was tough because gluing both sides of a fitting sucks. I was referring to the coaxial cannon.

[OuchProgramme]

Hmmm question.
Why dont you just use the blowgun trigger itself instead of the wooden rod?

[kablooie]

I did not use the blow gun trigger because it is not in the right position (it would be behind my shoulder during firing) so I used the dowel to move it forward.

[bigbob12345]

A very nice set of guns you got there My favorite is the golf ball one(I just seem to really like any gun that fires a golfball).
And by the way duct tape wont help if there is a failure it just makes it worse.
You should give them all a paint job it would really help the looks of the cannons.
You look like you have quite a lot of potential in this hobbie you have accomplished some pretty nice guns and I assume you havent even been intrested that long.
Great job :thumbright:

[kablooie]

I have been making potato cannons for about a year, but intermittently, every two months or so i check in and then make something when I have a lot of free time. I spent months of intermittent weekend work on a semi auto idea that ended in when the stupid thing broke in half. The duct tape is not to protect from explosions (I read that thread too, kind of scary) but to protect from sun exposure and just to cover the primer. Do you have any ideas on a non-intimidating color choice for paint? Anyway, for my next project I want to build a piston valve or some other high-powered valve. Thanks for the feedback!

[Wannabedogbert]

I've been trying for ages to get mine to work, and I've run out of ideas. Everything I try just goes "fump" and breaks... If you don't mind telling me, what were your plans?

[bigbob12345]

The duct tape is not to protect from explosions (I read that thread too, kind of scary) but to protect from sun exposure and just to cover the primer.

Ahhh thats clever it is used to protect from sun exposure thats a good idea I think Ill do that on all my launchers.

[kablooie]

@ Wannabedogbert Sorry to get back to you so late, but I don't understand you question, is plans for a piston valve your looking for? Or is it semi auto plans?

@ bigbob12345 it does work pretty well, although painting does give you more color choices. Also, it is possible that the duct tape would also a lessen the impact of dropping the gun, although it would have to hit an area that has been covered. Even then, it could be that the duct tape would have no effect at all, but I bet if you put enough on there it would help at least a little.