A grill lighter is disassembled and used as the heat source for the steam production along with some copper plumbing parts and 1/2" copper pipe. Some water is placed inside the barrel, a potato plug is inserted as an air seal and projectile, and a cork is used as a sudden pressure release. The flame from the lighter heats water to steam and the pressure increases in the barrel until the cork and potato can't hold anymore, then it pops and launches the potato to wherever it's pointed.
This is a prototype steam potato pistol and can be taken a lot further, but I'm just sticking to functioning basics here. Someday I would like to make one with a pressure gauge, quick release valve, and a better handle with the fuel stored inside the handle. I'm calling this version the SPPP1.
It is a little dangerous to build and use because of the flame and hot surfaces, flying objects, and steam; be careful. Playing with fire, pressure, and projectiles is always risky, even on this small scale. Don't shoot an eye out, I'm not liable for any injuries you incur with this. ;( What happened to that "not liable" category of Instructables anyway?
- Various short wood screws
- Some leather strips from an old belt to hold the fuel bottle
- Some scrap wood for a handle
- Lead free plumbing solder and flux
- 4" length of 1/2 inch copper pipe
(3) 1/2 inch copper ST 90 degree elbows
(1) bag of copper plumbing pipe brackets
(1) candle/grill lighter
Step 1: Start Plumbing the Boiler and Barrel
Attach the three elbows together at the end of the barrel to form a curl and put a cap on the last elbow.
Dry fit all the parts as shown in the photo. Make the elbows form off to the side so a flame can heat water inside the cap.
Step 2: Sweat Those Pipes
Gdawg at Instructables has a nice tutorial on How to Sweat (solder) Copper Pipe
Step 3: Make a Handle
Step 4: Attach the Fuel System
Bend a pipe bracket and attach it to the side of the handle so that the flame will burn just under the copper cap or boiler.
Insert the piezo clicker into the handle to make a trigger; this is what makes the spark to ignite things. Ground the black wire to the barrel and the long white wire gets routed to the ignition point under the boiler.
Screw a piece of leather to the handle and wrap it around the back to the other side. Fit the butane bottle in there and attach the leather again with a screw. This should hold the tank snuggly, but also let it slide a little. The slide switch to open the fuel valve hangs nicely on the leather strap. To turn on the gas you just push the butane bottle down a little until you hear the hissing; to turn it off you slide the tank up.
Now route the fuel hose and metal tip to the newly attached bracket under the boiler. Wrap the white spark wire around the base of the metal tip. Attach it in the hole with a twisty tie or something and use pliers to bend it so the flame base will be 1/4" under the boiler. The spark should jump from the metal tip to the bottom of the boiler, if it doesn't adjust the bracket until it happens.
See the pictures on all the above stuff.
Step 5: Add Water, Plug, and Shoot.
Cut out a potato plug using an extra piece of scrap pipe and insert the plug into the barrel. This should have an airtight seal and want to push back out, it should not go far into the barrel.
Wedge the cork into the barrel; don't overdo it.
Move the butane bottle down to open the fuel valve.
Click the piezo clicker to ignite the flame.
Point and wait about 1 to 2 minutes.
POP! The spud should fly; mine has a range of about 25 to 35 feet.
If it takes much more than 2 minutes to pop, then turn off the flame and let it cool off for a while; either the air leaked around the potato and cork or the cork was in too tight.