My New 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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Hubb
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Wed Apr 09, 2008 9:25 am

This is my latest completed project: an advanced combustion launcher.

Chamber: 3" Sch40, 109cu in
Barrel: 1.5" Sch40, 44" long
Fuel: Metered propane, mixing fan
Ignition: Stun Gun, centered triple spark

The spark strip is made from a split piece of 1" Sch40. The screws are bent to produce the spark at their tips. It also holds the chamber fan and is completely removable / serviceable by removing two screws. Basically, it is a combination of Burnt Latke's spark strip and chamber short with a fan added to its end. I've included a sketch to better explain since I secured it in the chamber before I took a picture of it.

Grip tape is wrapped around the barrel for easy removal for breech loading. It is also wrapped around the end cap and handle. A rechargeable battery is used to operate the fan and is held on to the chamber with velcro. All wires are housed in the handle, which is made of 1" Sch40 and two 45 degree elbows. The propane tank holder is mounted directly under the chamber to even out the balance. It is finished up with black and silver paint.
Attachments
launcher
launcher
chamber
chamber
fan switch and rechargeable battery
fan switch and rechargeable battery
meter
meter
breech loading barrel
breech loading barrel
chamber internal, from rear
chamber internal, from rear
chamber internal, from muzzle
chamber internal, from muzzle
08.JPG (33.73 KiB) Viewed 4563 times
sketch of spark strip
sketch of spark strip
07.jpg (16.95 KiB) Viewed 4563 times
half inch thick plywood versus a potato
half inch thick plywood versus a potato
back of plywood (after three shots)
back of plywood (after three shots)
homemade "dart"
homemade "dart"
1 inch thick cement
1 inch thick cement
dart after impact with cement
dart after impact with cement
cement after impact with dart
cement after impact with dart
Last edited by Hubb on Thu Apr 16, 2009 7:44 am, edited 2 times in total.
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biggsauce
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Wed Apr 09, 2008 9:53 am

Yessir, i like. Clean chamber innards and the rechargable battery pack... nice touch.

What are you holding your tank in the pipe with? Magnets?
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Hubb
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Wed Apr 09, 2008 9:56 am

Actually, I considered a magnet but I cut slits and ran the hose clamps through the tank holder. The friction from hose clamps passing through the holder holds it in just fine.
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jrrdw
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Wed Apr 09, 2008 9:59 am

Nice build! Does your plywood have panaling on one side? Would have been sweet to get a video of that dart destroying that concrete, WHAM! What did that sound like when it hit? I also like your paint scheme, simple. Looks good I think.
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biggsauce
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Wed Apr 09, 2008 10:00 am

Ah alright cool.

The battery pack powers the stungun too right?
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Hubb
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Wed Apr 09, 2008 10:05 am

I wanted to paint it blue, to match the Tippmann Model 98 I just rebuilt, but I realized I ran out of blue paint. As far as the sound, it wasn't too loud, but it was enough to get my wife's attention (who was outside and not expecting it :twisted: ).

The plywood did have paneling on it. It came off the side of my house when I put a new siding on it. It was also painted, which just added to the back shot.

biggsauce: The battery pack just controls the fan. The stun gun has it's own battery compartment.
Last edited by Hubb on Wed Apr 09, 2008 10:07 am, edited 1 time in total.
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starman
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Wed Apr 09, 2008 10:07 am

Shhwweeet spark and fan setup. A good spark system has been bedeviling me somewhat and this looks great! I think I'll steal this idea and run with it. :) I like the handle and grip you have there too.

Otherwise, my other comments would be rip the guts out of that crooked stungun and mount em in a rectangle box....maybe hide the battery pack as well.

You must be left-handed...??? :wink:
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Hubb
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Wed Apr 09, 2008 10:09 am

starman wrote:You must be left-handed...???
How did you guess? Eventually, I will gut the stun gun, which is why I only secured it with a hose clamp. I was just ready to shoot this bad boy.
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lockmanslammin
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Fri Apr 11, 2008 2:29 am

Nice ingenuity, I like how the fan is held in by the spark strip body and is removable with it.
So is that a 9v battery pack? If so I'm assuming that is a 12v fan....
How does 9v get it going for you?

^^^a lot of assuming going on in that little set of questions...hehe,

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Hubb
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Mon Apr 14, 2008 12:27 pm

The battery pack came from an airsoft rifle I had. I'm not sure on the voltage, but it is enough to run the fan and does so quite well.

I'm dropping the stun gun from it. Because of the removable spark strip, I am trying to install an electric grill igniter, which will run off of the same rechargeable battery. A downgrade, I know, but it works and I need the stun gun for my hybrid, which is going through a makeover as well (I want to put a golf ball through some stuff :wink: ).
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lockmanslammin
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Mon Apr 14, 2008 10:05 pm

You will be having to narrow your spark strip gaps pretty dramatically for that grill ignitor to be reliable. To bad to see the stun gun leave the cannon, but it sounds like you have bigger better things in line for it so....thats all good.

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Hubb
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Tue Apr 15, 2008 11:17 am

The beauty of my spark strip design is that it is not only removable, but it can be configured any way I need it to. With that said, I wired the electric grill igniter to the strip so that it produces the spark through the center gap only, then bolted it back in my launcher. I've noticed no performance loss. In fact, I punched a hole in my pecan tree that is about 1.5" deep with another pvc dart.
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Spuddin
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Tue Apr 15, 2008 12:23 pm

sweet weapon, looks like a powerhouse, i like it. btw the battery pack looks like maybe about 9 volts. i powered up a couple 12 v pc fans i want to use in one of my guns with 9 volts but they spin kinda slow, do u have this problem?

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Hubb
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Tue Apr 15, 2008 12:41 pm

The only time the fan spins slow is when the battery drains. Otherwise, I can't really tell a difference in spinning 9v versus 12v.
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Blitz
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Tue Apr 15, 2008 1:54 pm

Beauty!

No idea how I missed this. That spark strip/chamber short is about what I'm making for my cannon -- nice work man.
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