Small Pistol-Grip Combustion

Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
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CrashTestDummy II
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Fri Jan 16, 2009 12:14 am

This one's been like, 95% complete for a month or so now, and all I had left to do was attach the handle to the body of the gun.

The chamber is 2" x ~6" and the barrel is 1/2" SDR 13.5 x 16" long. I've been using a ton of the 1/2" SDR 13.5 pipe lately because I have a bunch in the basement that I found when I moved here. It's perfect for paintballs. No wadding or sabots needed.

Ignition comes from a standard piezo BBQ ignitor, which is mounted in the pistol grip and there are two spark gaps in the chamber.

The barrel shroud thingy (pardon the terminology) is simply there to make it look cool. It doesn't really have any other function.

Basically, all I had left to do today was screw on those little metal brackets that hold the handle to the chamber. You can see that the handle was made originally to be held on with hose clamps, but I changed my mind because they didn't look good on the gun.

Anyways... Here are the pictures :)

<a href="http://i119.photobucket.com/albums/o139 ... .jpg"><img src="http://i119.photobucket.com/albums/o139 ... view-1.jpg" height="170"></a> <a href="http://i119.photobucket.com/albums/o139 ... .jpg"><img src="http://i119.photobucket.com/albums/o139 ... Detail.jpg" height="170"></a>

<a href="http://i119.photobucket.com/albums/o139 ... .jpg"><img src="http://i119.photobucket.com/albums/o139 ... hamber.jpg" height="170"></a> <a href="http://i119.photobucket.com/albums/o139 ... .jpg"><img src="http://i119.photobucket.com/albums/o139 ... rkGaps.jpg" height="170"></a>

<a href="http://i119.photobucket.com/albums/o139 ... .jpg"><img src="http://i119.photobucket.com/albums/o139 ... Shroud.jpg" height="170"></a>

Below are two diagrams, to better explain how it was made. They look a little funky, but it's just from being compressed into a thumbnail. Click on them for clearer image. Note that the chamber looks bigger from the outside of the gun than it actually is. (The diagrams were made as close to scale as possible without spending hours in MS Paint, however they aren't scaled exactly.)

<a href="http://i119.photobucket.com/albums/o139 ... .jpg"><img src="http://i119.photobucket.com/albums/o139 ... annon2.jpg" height="170"></a>

The next diagram is showing where I removed material from the handle to accommodate the BBQ ignitor and wires. Any excess space around the ignitor was filled with hot glue to keep it from wiggling around inside the handle.

<a href="http://i119.photobucket.com/albums/o139 ... .jpg"><img src="http://i119.photobucket.com/albums/o139 ... iagram.jpg" height="170"></a>
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LCTChamp
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Fri Jan 16, 2009 12:24 am

Nice Gun! I love the wooden handle. Did you make it yourself? The "barrel shroud thingy" looks pretty cool. You would get better performance with a longer barrel, but then it wouldn't be a pistol.
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starman
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Fri Jan 16, 2009 1:53 am

Really nice pistol! I do like the handle with its special ignitor cavity a lot, but to me, the lined up screws in your chamber speaks volumes. It isn't easy to pull off that screw installation as neatly as you did here.

A tiny fan and metered propane would really put the icing on this one.

I'm dropping it in my favorites... :wink: Great job on the drawing and pictures as well!
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Cosmic Muffin
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Fri Jan 16, 2009 3:19 am

looks great :wink:
the grip is very well done, looks tops.
good job
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Combustion Monkey
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Fri Jan 16, 2009 10:41 am

I like it a lot and have been kicking around the idea of a little paintball gun. How does it load, down the barrel or unscrew in the center for a breechloader?
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CrashTestDummy II
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Fri Jan 16, 2009 12:43 pm

Thanks for the feedback :)

@ Ictchamp - I made the wooden handle myself. It's made of two pieces of plywood that are nailed together.

I didn't bother making some kind of breech-loader for this one. Just a muzzle-loader. I figured that the shroud was too robust to be threading on and off.
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starman
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Fri Jan 16, 2009 1:08 pm

CrashTestDummy II wrote: @ Ictchamp - I made the wooden handle myself. It's made of two pieces of plywood that are nailed together.
Derrr uhh, nailed?
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CrashTestDummy II
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Fri Jan 16, 2009 1:37 pm

:lol: With a nailgun, of course! The nails are really small, and if you look at the picture that's a close-up of the grip, you can see little divot things where the heads of the nails went in.
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starman
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Fri Jan 16, 2009 1:47 pm

CrashTestDummy II wrote::lol: With a nailgun, of course! The nails are really small, and if you look at the picture that's a close-up of the grip, you can see little divot things where the heads of the nails went in.
That's cool, just hit me a little funny. You would usually glue and clamp plywood in a situation like this.
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CrashTestDummy II
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Fri Jan 16, 2009 2:50 pm

Yeah, I thought of gluing the two halves together, but I didn't because I didn't want to have to wait for the glue to dry :roll:
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burke_a_lot
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Sun Feb 08, 2009 3:34 am

looks like a WWII welrod

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"I ran.... out of.... ammo.... thats never happened to me before...."
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