I would like to start by giving credit to robbtoberfest and his Steam Powered Potato Pistol 1.0 design which can be found here:
I also want to start by re-iterating his safety warnings as this device has risks related to fire, steam, pressure, metal-work, and projectiles. I recommend wearing eye protection during all steps and using common sense. I accept no liability for any risk in the manufacture or use of this device. Do not attempt to use power tools if you are not familiar with them and I don't recommend anyone under the age of 18 attempt to manufacture this device without competent adult supervision. Don't touch the barrel for a few minutes after it has been fired as it becomes extremely hot. Also, the soot will stain clothes/skin. Be careful with this thing guys.
I will leave the construction of the barrel/chamber assembly to robbtoberfest's design and will primarily focus on the design modifications which allow the fuel/heat source to be a "Zippo (tm)" brand lighter. The only modification I made to the barrel/chamber assembly is that I used "J.B. Weld (tm)" brand two part epoxy paste instead of solder. I find that it is less messy and I have limited experience with solder. The joints and air-tight seals of the "J.B. Weld" have held through all of my test firings. The farthest I have gotten it to shoot a plug his about 23 feet.
It works, but it has limitations. I feel that it would work well indoors with very minor drafts, but outside it is challenging to keep the flame on the chamber if there is any wind at all. Seems to take me at least a couple minutes of fairly steady flame on the chamber to get it to fire. I am not sure if this modification is faster/slower to fire. I think indoors it is probably about the same to a little faster to fire.
Step 1: Components/ Tools
Barrel/Chamber assembly from the following instructable:
***The only modification is I used J.B. Weld instead of solder.
Oak plank - In the "craft wood" section of Home Depot - about $2.50
- Pine would be cheaper and would probably work fine. I would expect pine to burn a little easier so I chose oak.
Anvil (or hard surface like a piece of metal or wood to hammer against) / hammer
Pliers. Two needle nose would work fine.
Zippo (tm) brand lighter - usually around 18 bucks. Of course you will also need lighter fluid.
Bolts and corresponding wing nuts/ short wood screws. (I used brass, but that was mostly for show. Frankly, I think it may have been better with steel as I broke the heads off of a couple of them trying to screw them into the oak even with pilot holes. I suggest using bar soap on the threads to lubricate them as they screw in.
A drill or dremel with a drill bit to make pilot holes and drill through a couple of copper pieces.
A good table mounted vice makes life a little easier to bend the copper fitting (to be explained).
A hack saw is one option for cutting the pipe. I used a pipe cutter.
A file for deburring and cleaning out the lip on the barrel and corer.
Leather scrap or denim or any thick material as a place to store your plug cutter. Attached with furniture brads.
- Apparently they come in terms of "numbers". I found that #5 size seems to fit the 1/2 inch copper pipe best.
Potato. Not too thick. I wouldn't go much thicker than an inch.
Eye dropper or other device that can dispense about 8-10 drops.
A long wood screw is useful when you accidentally load the potato before you put the water in. I know it sounds stupid, but I have done it twice now. Just screw it into the potato and pull. Also useful if it doesn't fire for any reason.