Introduction: Homemade Solo Style Fire Pit/Stove
I have been tinkering with homemade wood gasifier stoves made out of soup cans for hiking. It has been so successful that I decided to try making a large model in the vein of the Solo backyard fire pits that have been popular online.
I am not an expert on the physics of how these work, but in a nutshell a wood gasifier burns wood and channels superheated air to the ports around the rim. This air ignites the escaping wood gasses that usually drift away as/with smoke. When made and operated correctly these stoves produce no smoke and burn fuel efficiently, and pretty much completely...only powder typically remains if left to self-extinguish.
For this project I had a leftover helium tank from a birthday party to start with.
Helium or Propane Tank
Steel Bain Marie Pot (found online or at restaurant/cooking supply stores)
Angle grinder with cutting and flap wheels
Drill and Bits
Step 1: Prepare Outer Container
I took an old empty Helium tank and marked a circle on the bottom that was the diameter of the Bain Marie Pot bottom. Using an angle grinder and cutting wheel I cut out the hole. I had to use a flap wheel to size it so that the entire Bain Marie Pot would slide all the way in with the lip of the pot sealing to the tank.
Step 2: Drill Vent Holes in Tank
Draw a line around the lower edge of the tank. Divide the line for your vent hole centers. I went with 32 holes for the "side rim" and 16 additional holes on the "bottom rim".
Center punch the holes. Drill pilot holes then make the vents with a Step Bit. I drilled the main ring to 1/2" and the bottom ring to 3/4".
Step 3: Drill the Burn Chamber Vents
Now you have to ventilate the bottom of the Bain Marie Pot and drill the gas vents in a ring around the top.
Much like with the Tank...draw your line and divide it for your hole centers. I made 36 gas port holes along the top. The bottom can be vented with any number, size or pattern of holes you desire, just make enough to get a good draft of air up through the bottom. Some people make these with a grate/grill in the bottom vs holes.
Note. These Bain Marie pots are Stainless Steel. Drill at low speed and with oil. It was time consuming (but obviously possible) with a hand drill. A drill press would have been easier.
I used alternating 1/4" and 5/8" bits for the gas ports and assorted (pretty much random) sizes on the bottom.
Step 4: Assemble
Now all you need to do is slide the Bain Marie Pot into the Tank till seated.
Step 5: Use
Fill the inner chamber with thumb sized (or slightly larger) pieces of dry wood up to, but avoid going over, the gas ports.
Light from the top. I use a cotton round dipped in wax or cotton balls smeared in petroleum jelly as starters.
Let it burn till you see the gas ports emitting tongues of flame. Once a bed of coals is established in the bottom it's easier to generate more wood gas by feeing in fresh fuel. Feed the fire gradually to maintain a balance of fresh wood and strong gas port burn. If you overfeed with fresh wood the ports may stop and you may get some smoke. Strong winds may effect performance.