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UNDER CONSTRICTION

After I melted Econo Gun II's Combustion chamber, I pretty much ditched that design and went to
rebuild my first Potato Cannon with many improvements over the original Econo Gun design.
This was originally pasted on to the Econo Gun II page and progressed but I've decided to make a
separate page for it.

Construction:(Added Nov 8, 3005)

Building Econo Gun III is very similar to the original Econo Gun. You can also look at the pictures at the bottom for reference.

You will need:

2" or 3" diameter ABS drain pipe. (I used a 3" pipe because I had one but 2" is recommended as there are not a lot of projectiles that would fit snugly)

Heavy Duty Duct Tape (Don't use the cheap stuff; recommend 3M)

Any plastic jar with a mouth that would fit the inside diameter of the pipe

BBQ Ignitor (Char Broil Universal fit Hot-Shot).

Instructions:
First, wire up the BBQ ignitor. I originally started with two wires going into the chamber with the ends about 1/2" away to form the spark point. It worked but wasn't good for long term use as the insulation on the wires eventually melted and caused short circuits. I ended up using a sparking electrode from a bbq grill but these parts are hard to find (You should get one if you purchase the Hot Shot ignitor kit).

Place the wires along side the lip of the jar so the electrode is resting inside the jar. Fold the wires over the lip.

Tape the jar and the ignition wires to one end of the pipe. Make sure you apply the tape securely!

Attach the ignitor to wires; you're done. Now find some fuel and ammunition.

Notes on my Experiences:

Update: November 26, 2004
I found pieces of my original Econo Gun and decided to get it working again. Anyway, instead of using a can to seal the back end, I found a plastic jar that once held instant coffee. It made the perfect chamber. This improved version also has a piezo barbecue ignitor instead of the old "fuse hole". I still need to work on the ignition system though; right now, the spark electrodes are nothing more than just two wires going into the pipe which need to be readjusted frequently. Everything is held together with 3M's Scotch Transparent Duct Tape (Don't Laugh)

I manage to shoot a tennis ball container around 55-60 feet. I used Rave "Mega Hold" hairspray as the propellant.

Update: December 23, 2005

I really need a better ignitor as I have to readjust the points a lot. I fired my cannon a couple times today until I ran out of hairspray.
Hairspray by far is the weakest of all fuels and leaves a sticky residue all over the inside of the barrel and chamber. I'll try deodorant
or even diethyl either (starting fluid) later when I can obtain them. I also need to get a better piezo ignitor/generator; the one I'm using right now is starting to wear out and I need to press it 3-5 times before the fuel ignites.

Update: Feb 15, 2005

I fired my cannon again just last Saturday (Feb 11). This was the first test on propane, I lost my tennis ball container somewhere and when I found it, it had melted due to the heat. My next projectile may probably be an orange, I have an orange tree in my yard that grows large ones. I may also plan to use softballs as well.

I also got a better ignitor, it's a "Hot Shot" universal fit replacement ignitor by Char-Broil with a specially designed collector box that concentrates the gas. Works better than just 2 bare wires in the chamber. You can get this at LOWE'S for about 10$

I just used half the collector box with the electrode exposed.

Update: March 2, 2005

Just last weekend, I got my new ignitor working better using just the electrode (no collector box) and tried Silicone Lubricant for fuel. The muzzle blast was very impressive but I didn't have any projectiles to shoot so it was only blank shots for that day. Try around 10-15 seconds of spray and use a little more or less as desired. Since using Silicone Spray, I have gotten a major improvement over hairspray or propane. In fact, the blast is so strong now that I actually feel nervous about firing that thing !

Update: May 19, 2005

OK, I tried to fire it today on butane but it doesn't seem to be working right now. I plan to take it apart sometime later to clean and adjust the ignition electrode. I may post some pictures as well.

Update: May 25, 2005

I took the gun apart to clean the ignitor and replace the tape that was coming loose. I repositioned the electrodes as well. It still didn't
fire until I swapped the pezo generator with the one on my BBQ. It still sparks but it's probably wearing out (Note, the last time I bought an ignitor, I put the new generator on my BBQ and used the old one on the cannon.
 Anyway, I launched some rags out into the street with butane but it took a while after each firing before I could make the next shot. I probably have to air out the combustion chamber so there's fresh air for the next firing. I might have to buy a can of silicone spray or other propellant; the silicone spray I used was my neighbor's

Update: June 4, 2005

Well, on Thursday, I tried the cannon again and it still had trouble firing. I cleaned the ignitor and repositioned it again. This time, I used a lot more butane that normal for a blank shot which I did in the garage and after the second click, there was a huge whoosh and flame. I almost thought the muzzle blast blew out my garage door but it didn't; just a good rattle. It should be ready for more shots but I ran out of gas though. Got to find some more fuel. I have propane on hand and other propellants that may be used.

Update: Aug 2, 2005

I hadn't played with the cannon for a long time so I took it out again today. I also decided to take the electronic ignition device out of our furnace to spark the cannon. It ran on 24 volts AC but the only transformer I had to run it outside the furnace was a 16 VAC transformer for a model train. It worked but the spark was not that bright. I disconnected the BBQ ignitor and hooked the wires onto the ignition box and attached it to the transformer which was powered by an extension cord running back into my den. After hooking everything up and testing for spark, I injected 15 seconds of propane from a grill regulator into the cannon then went back inside to plug in the ignitor. At first, nothing happened except the "Tick Tick Tick" of the ignitor sparking but then 5 seconds later, it caught and there was the familiar "Whooosh-Poof" of the cannon fireing.
 OK, after that, I refueled it and tried again but this time, it wouldn't ignite. I let it air out for a few minuets but still nothing. Noticing how the tape holding the cannon together was coming loose, I took the cannon apart to replace the tape (I used regular duct tape this time and cleaned the ignitor. When I resembled it, I decided to put the electrodes on differently so now it was facing the back of the cannon rather than towards the front.
 I finally was able to shoot a lemon but when I was reloading it, my dad came home and he made me put away the equipment and clean up the mess I made. There was still some propane left in the cannon even after I had disconnected the electronic ignition so when I hooked the BBQ ignitor back up and sparked it, it fired on the first click. I guess I finally figured out a better position for the ignitor.
Well, that's all for now.

Update: Aug 3, 2005

I'm storing the cannon in my room now and took some pictures. Place arrow on picture for more info

The cannon itselfClose up of ignitor

Coffee jar combustion chamberLooking down the barrel

Holding the gunAnother way to hold (Commonly called bazooka style)