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New to this, just made two spud guns, holes in .5" plyw

Unread postPosted: Mon Sep 01, 2008 2:05 am
Author: kiwi of nitro
I race nitro RC truggies, and one day I left a few head shims out of my engine after a rebuild and it caused detonation to occur in the combustion chamber (fuel and air mixture explodes rather than burns which damages engine), it blew the glow plug out of the head button with a gun shot like sound when I hit the throttle destroying my glow igniter which was on the glow plug at the time.

Anyway, it made me start thinking about building a cannon that operated like an engine. (igniting a mixture of fuel and air with an electric charge and using the energy released to drive a projectile rather than a piston).

So I went to Home Depot and started buying a bunch of piping, fittings, cements, sealants, and a piezoelectric igniter.

Built two guns, I have a video of me using one of them.

Click here for video of small spud gun.


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Daiwa sticker :roll:

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Used RTV and screwed the igniter into a 5/8" hole in the tee joint. That's 1.5" barrel and 3" chamber.

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Igniter leads run inside the chamber and come through a small hole where they are attached to 2 large bolts that create the spark in the chamber.

They are attached to the bolts with hex screws.

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That wire in between allows me to adjust the gap.


NOW FOR CANNON #2 THE WHOPPER!!!


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That's 4" chamber and 1.5" barrel.

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I made the igniters removable by bolting them on and then sealing them with rtv.

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The spark jumps to one of 8 prongs on part of what was the gas concentrating vortex that came with the igniter, it is suspended by a small cable from an old dremel snake.

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Notice the stopper in the barrel, that is present in both my guns.

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Nitro cleaner is pure methyl alcohol, my favorite fuel.

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This target was shot from about 60 feet away with the whopper, this picture shows the back side of it, it's a half inch of plywood.

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a couple shots hit the wheel barrow

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Those are my cannons



-Matt

Unread postPosted: Mon Sep 01, 2008 2:46 am
Author: starman
Fairly decent guns here. The duct tape takes away from the look of the gun. I can't imagine why it's necessary for it to be on there. Next time, design your build without including using duct tape anywhere on it.

Also, your spark gaps seem more complicated than they need to be. It isn't necessary to use the gap bracket/holder that comes with the BBQ ignitors. And, how does the wire between the bolt heads allow you to adjust the gap?

I've used methol alcohol with a little nitro methane mixed (RC fuel) as spudgun fuel before and can attest it works well for a spray and pray gun. Your next gun however, you should plan to move to metered propane.

Good effort though and Welcome to Spudfiles!

Unread postPosted: Mon Sep 01, 2008 2:53 am
Author: ALIHISGREAT
nice cannons but that pipe doesn't look pressure rated, for your next i would use pressure rated because 1. its pressure rated so safer (duh!) 2. it looks better because its smoother and less angles, cluttered, indented or whatever.

Unread postPosted: Mon Sep 01, 2008 6:08 am
Author: CasinoVanart
Silastic is good!

Unread postPosted: Mon Sep 01, 2008 9:10 am
Author: TurboSuper
That's a cool cannon. It seems to be made of ABS, which is great for added safety. I also thing the duct tape compliments it's "ghettoness" quite well, in this case.

The ignition system seems a bit bizaare, but I guess if it works, then it's all good :D

Unread postPosted: Mon Sep 01, 2008 12:39 pm
Author: frankrede
ALIHISGREAT wrote:nice cannons but that pipe doesn't look pressure rated, for your next i would use pressure rated because 1. its pressure rated so safer (duh!) 2. it looks better because its smoother and less angles, cluttered, indented or whatever.
Your point is? I would think someone with over 1000 posts would think more.
This is a basic combustion, NSF-PW isn't really that necessary.