Building a better potato gun?
#1
12-02-2006, 10:38 PM
Join Date: Feb 2006
Location: Eau Claire, WI
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Building a better potato gun?
Allright, It's time for a better potato gun...
Right now, this is my setup...
18" of 4" PVC for the expansion chanber, a 3" to 1.5" adaptor (with a reducing bushing), and 36" of 1.5" pvc for the barrel. I'm using a BBQ ignitor for spark, and I'm routing it through 2 screws, that I put in the barrel at an angle to eachother and they spark in the middle of the tube... They're about halfway down the expansion chamber. I'm using starting fluid for fuel.
1st problem is... Unreliable spark. It never goes off on the first click, it usually takes a few before it goes (if it will)
2nd problem is... Improper fuel mixture. I usually take the end off the barrel, and set it into the wind for a few min, to clear it out... Then, I spray a very quick shot of starter fluid into it... I'd like a way to clear out the barrel faster, or just a way to use a consistaint amount of fuel...
3rd problem is the ignitor itself... It's kinda stupid to hold a BBQ ignitor, I want something cooler, or mabey a handle with the ignitor hardwired to the inside of it.
Any suggestions?
Tks alot
~Nate
Right now, this is my setup...
18" of 4" PVC for the expansion chanber, a 3" to 1.5" adaptor (with a reducing bushing), and 36" of 1.5" pvc for the barrel. I'm using a BBQ ignitor for spark, and I'm routing it through 2 screws, that I put in the barrel at an angle to eachother and they spark in the middle of the tube... They're about halfway down the expansion chamber. I'm using starting fluid for fuel.
1st problem is... Unreliable spark. It never goes off on the first click, it usually takes a few before it goes (if it will)
2nd problem is... Improper fuel mixture. I usually take the end off the barrel, and set it into the wind for a few min, to clear it out... Then, I spray a very quick shot of starter fluid into it... I'd like a way to clear out the barrel faster, or just a way to use a consistaint amount of fuel...
3rd problem is the ignitor itself... It's kinda stupid to hold a BBQ ignitor, I want something cooler, or mabey a handle with the ignitor hardwired to the inside of it.
Any suggestions?
Tks alot
~Nate
#2
12-02-2006, 10:50 PM
Fleet Owner
A propane torch will always give the proper air/fuel ratio. It's under pressure too, so it will displace the exhaust gasses while charging. You can get one of the self igniting ones that have the igniter built in.
Or you could get a lot of crazy and use acetyline as fuel. But it's too powerful to use with plastic pipe. I played around with calcium carbide and water when I was a kid using galvanized water pipe with a tiny hole drilled in the side of the breach end, and was frequently surprised at how far it would toss an empty tin can set over the end of the pipe. If you decide to use a cutting torch and charge it with oxy/acetyline, then it gets VERY dangerous. You can kill yourself if you do the wrong thing or at least end up in the hospital with them picking pieces of pipe out of your butt.
Or you could get a lot of crazy and use acetyline as fuel. But it's too powerful to use with plastic pipe. I played around with calcium carbide and water when I was a kid using galvanized water pipe with a tiny hole drilled in the side of the breach end, and was frequently surprised at how far it would toss an empty tin can set over the end of the pipe. If you decide to use a cutting torch and charge it with oxy/acetyline, then it gets VERY dangerous. You can kill yourself if you do the wrong thing or at least end up in the hospital with them picking pieces of pipe out of your butt.
#5
12-03-2006, 09:30 AM
Here is what i did....i built two, and both launched potatoes well over 100 yards.
I can't remember the pipe size, but for the combustion chamber, me and my friend used a coupler that upsized to about 4-5", and used a pipe cleanout cap on the very end. We just unscrewed it, sprayed lysol in it. We put the potato in first, then sprayed it, then capped it.
I used a lantern lighter, its a deal you twist with your finger to cause a spark. It worked the first time, every time. Also, i attached a string to it that we wrapped around the shaft so we could launch the gun like a grenade launcher, over the shoulder. Then just pull the string sharply, and as it unraveled off the lighter, it spun it, causing a spark and it went off.
I can't remember the pipe size, but for the combustion chamber, me and my friend used a coupler that upsized to about 4-5", and used a pipe cleanout cap on the very end. We just unscrewed it, sprayed lysol in it. We put the potato in first, then sprayed it, then capped it.
I used a lantern lighter, its a deal you twist with your finger to cause a spark. It worked the first time, every time. Also, i attached a string to it that we wrapped around the shaft so we could launch the gun like a grenade launcher, over the shoulder. Then just pull the string sharply, and as it unraveled off the lighter, it spun it, causing a spark and it went off.
#6
12-03-2006, 11:18 AM
any pumpkin launchers here?
Just about a month ago, they held the annual world championship competition in southern DE.
Several categories, but the giant air cannons can shoot a ten pound gourd nearly a MILE! (no new records this year; I think it's about 4400 ft.)
for more info: punkinchunkin.com
Just about a month ago, they held the annual world championship competition in southern DE.
Several categories, but the giant air cannons can shoot a ten pound gourd nearly a MILE! (no new records this year; I think it's about 4400 ft.)
for more info: punkinchunkin.com
#7
12-03-2006, 01:12 PM
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#9
12-03-2006, 03:43 PM
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Theyre right, put a clean out on the end of your expansion chamber, you just unscrew it, spray ur fuel, put it back and ignite. Ive had the same problem with the ignitor, chec ur nails they might not be at a good distance. Also, when I tried starter fluid it always seemed to condensate to quickly back into liquid and then wouldnt ignite since it was no longer an aerosol. Also, it tends to coat the nails, preventing them from sparking. Ive heard aqua net is the best, but I had the same problems with that too. Oust air sanitizer has never failed me.
My biggest gun: a 4 inch 45 degree adaptor (meaning 2 expansion chambers). th expansion chambers are just the length of the 45 piece with a clean out on each (each one is about 18 inches long) adapter down to a 2 inch barrel, a little under 3 feet long. ignitor is wired in series to each chamber so each one ignites (positive wire to one nail on one chamber a wire in between the other nail in that chamber across to one nail on the other chamber, negative wire from the remaining nail back to the ignitor) Since it has 2 chambers of 4 inch and a 2 inch barrel, its a 4:1 ratio of combustion chamber size to barrel size (obviously the bigger the ratio the bigger the boom). It sounds like a real gun and shoots apples (my ammo of choice) so fast that you can hardly keep up with them if theres not much light out.
Have fun and be safe
My biggest gun: a 4 inch 45 degree adaptor (meaning 2 expansion chambers). th expansion chambers are just the length of the 45 piece with a clean out on each (each one is about 18 inches long) adapter down to a 2 inch barrel, a little under 3 feet long. ignitor is wired in series to each chamber so each one ignites (positive wire to one nail on one chamber a wire in between the other nail in that chamber across to one nail on the other chamber, negative wire from the remaining nail back to the ignitor) Since it has 2 chambers of 4 inch and a 2 inch barrel, its a 4:1 ratio of combustion chamber size to barrel size (obviously the bigger the ratio the bigger the boom). It sounds like a real gun and shoots apples (my ammo of choice) so fast that you can hardly keep up with them if theres not much light out.
Have fun and be safe
#12
12-03-2006, 04:37 PM
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I glued on a piece of 2" tubing, angled back at 10 deg, for the handle. The 2" tube was coped to fit the 4" tube, and a small hole was drilled into the 4" tube so that the wires from the bbq igniter could pass from the handle into the 4" tube. I glued in a short piece of 1/2" tubiing into the handle and mounted the igniter's push button in the end of it with black RTV. This arrangement gave me a pistol grip with a trigger.
I put a threaded clean-out in the back end of the combustion chamber, and I keep the threads coated with petroleum jelly so they won't get stuck. (I use hair spray for fuel.)
To make charging easier, I glued in a short, threaded nipple to the top of the combustion chamber and added a screw on cap. That way, all I have to do to charge it is screw off the cap, squirt the fuel in (3 blasts works best for my set-up), and screw the cap back on. I don't have to mess with the clean out plug unless I need to clean out (duh) the inside.
The business end is fitted with a 4" to 2" reducer. I made 2 barrels - a 2" and a 1 1/2" thats fitted with a reducer bushing to fit the 4-2 reducer. The barrels are removeable, and held in place with a 1/4-20 bolt and wing nut. That makes changing the barrels easy, and the bolt prevents the potato (or whatever - boiled eggs work nice) from being pushed too far and into the combustion chamber. My plan is to eventually make a barrel that's sized for a golf ball - I think I could probably make it all the way around the world with only one or two bounces.The barrels are filed to a sharp edge (with the bevel on the inside) so that they will cut the plug to a tight fit as it's being loaded. When it was done, I painted the whole contraption satin black, so that it looks like some kind of military grenade launcher.
I've had many discussions about alternative ammo, such as dog poop in a plastic bag for really unfriendly applications, and the boiled eggs that I mentioned (of course, the eggs need to be peeled first). If the eggs are wet they load easy and seal tight, which is the secret for distance. A carefully loaded potato cracks like a rifle when fired, and travels 200 to 300 yards.
As an aside, the potato remnants left from the plug cutting cook up real nice, but they taste like hair spray.
I put a threaded clean-out in the back end of the combustion chamber, and I keep the threads coated with petroleum jelly so they won't get stuck. (I use hair spray for fuel.)
To make charging easier, I glued in a short, threaded nipple to the top of the combustion chamber and added a screw on cap. That way, all I have to do to charge it is screw off the cap, squirt the fuel in (3 blasts works best for my set-up), and screw the cap back on. I don't have to mess with the clean out plug unless I need to clean out (duh) the inside.
The business end is fitted with a 4" to 2" reducer. I made 2 barrels - a 2" and a 1 1/2" thats fitted with a reducer bushing to fit the 4-2 reducer. The barrels are removeable, and held in place with a 1/4-20 bolt and wing nut. That makes changing the barrels easy, and the bolt prevents the potato (or whatever - boiled eggs work nice) from being pushed too far and into the combustion chamber. My plan is to eventually make a barrel that's sized for a golf ball - I think I could probably make it all the way around the world with only one or two bounces.The barrels are filed to a sharp edge (with the bevel on the inside) so that they will cut the plug to a tight fit as it's being loaded. When it was done, I painted the whole contraption satin black, so that it looks like some kind of military grenade launcher.
I've had many discussions about alternative ammo, such as dog poop in a plastic bag for really unfriendly applications, and the boiled eggs that I mentioned (of course, the eggs need to be peeled first). If the eggs are wet they load easy and seal tight, which is the secret for distance. A carefully loaded potato cracks like a rifle when fired, and travels 200 to 300 yards.
As an aside, the potato remnants left from the plug cutting cook up real nice, but they taste like hair spray.
#13
12-03-2006, 10:15 PM
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experiment with different fuel.
certan brands of hairspray work well. Airfreshener or lysol is also good.
I used a screw in cap for the chamber with the bbq igniter mounted through
the cap and sealed with lots of fiberglass resin I put two bare #14 single strand wires onto the terminals of the igniter and formed them to make the spark gap extend into the centre of the combustion chamber. This way the gap is adjustable and also comes out for cleaning easily.
you get a bit more distance if you just start the potato into the barrel, then charge the chamber with fuel, close it then push the potato the rest of the way in. This gives you a bit more compression.
as for ammo- a bit of wadded up newspaper goes in first, then you can shoot anything you want out of it....... Great way to make a 200 yd cast when your fishing
certan brands of hairspray work well. Airfreshener or lysol is also good.
I used a screw in cap for the chamber with the bbq igniter mounted through
the cap and sealed with lots of fiberglass resin I put two bare #14 single strand wires onto the terminals of the igniter and formed them to make the spark gap extend into the centre of the combustion chamber. This way the gap is adjustable and also comes out for cleaning easily.
you get a bit more distance if you just start the potato into the barrel, then charge the chamber with fuel, close it then push the potato the rest of the way in. This gives you a bit more compression.
as for ammo- a bit of wadded up newspaper goes in first, then you can shoot anything you want out of it....... Great way to make a 200 yd cast when your fishing
#14
12-05-2006, 11:35 AM
There is a book called "Backyard Ballistics". it has all kinds of cool things you can make that go "Boom" or shoot stuff, it is way cool! It does have the plans for a potato gun. It is very simple and works great, spittin the spuds over 200 yards. You can play with all kinds of tech designs, but why build the better mouse trap when the simple one works so good? You wont spend over 10$ including the igniter for this one.
Cheers,
Rick
Cheers,
Rick