Update: Root Simple reader Ruben questions whether it is possible to build a true rocket stove out of metal. Ruben sent me to a Facebook post by Benjamin Rosen who says, speaking of another metal rocket stove, “Actually, you can say that this is not a rocket stove. A rocket stove gives great heat from a small amount of fuel because it burns very efficiently at high temperatures. This is achieved by having a ceramic lining in the combustion chamber that permits very high temperatures because it insulates the combustion chamber, and because it absorbs and returns the heat to the chamber by glowing white hot. A metal lining, as we see in this design, will shed heat to the environment and therefore cannot reach the high temperatures needed for a true rocket stove. Metal, in any case, would melt at the temperatures achieved in a true rocket stove combustion chamber.“

Rocket stoves cook food with small pieces of wood efficiently and with much less smoke than conventional wood burning stoves. They also help prevent deforestation since you can burn small twigs trimmed off a tree rather than burning logs. Search the interwebs and you’ll find may different designs. But they are all based on burning wood in an “L” shaped tube to create a chimney effect. Insulating the tube increases efficiency.

A friend who lives in a remote part of Southeast Asia is visiting us this month and we wanted to come up with a design for a rocket stove that could be made from commonly available materials with nothing more than hand tools. Our goal was done rather than perfect. Here’s how we did it:

We settled on a simple design, using just a metal paint can, some sheet metal and nuts and bolts: supplies that can be found in the small village he lives in. As for tools we used a pair of tin snips, a pair of pliers, a nail, a hammer and a pocket knife.

The first step was to size the pipe and the holes we would need to cut in the paint can. According to the Aprovecho Institute, the height of the rocket stove should be no less than three times the diameter of the pipe. Make the pipe higher and you’ll cut down on smoke but lesson efficiency. Since the paint can we had was around 19 cm tall, we decided to make the tube around 6.3 cm.

The first cut was made in the top lid of the can.

We used a nail and hammer to make a hole for the tin snips.

We used a pair of pliers to bend over the rough bits of the metal. Again, our goal was to make something cheaply and quickly.

Next we cut a 6.3 cm hole in the bottom of the paint can.

Then it was time to fashion a tube out of sheet metal. In the US, it would be a lot easier to use stove pipe material, but it’s much easier to find sheet metal in the part of India my friend lives in.

We rolled the sheet metal into tubes.

We cut a slit in the vertical tube so that the horizontal tube could be inserted into it to form an “L”. It’s not a perfect fit, but with the insulation we added later, it works.

One of the problems with a lot of improvised rocket stoves is figuring out a way to hold the pot over the vertical tube. I realized that we could use five bolts and ten nuts to improvise a stand. We cut the first hole using a nail and tin snips.

We broke our “no power tool” rule to speed up the process.

Here is the top of the can with the bolts and nuts that will hold the pot just above the vertical tube where the heat comes out.

We inserted the horizontal tube and cut a notch out of the end, leaving a kind of shelf to hold the sticks we’ll use as fuel. This shelf ended up being a good idea.

We cut another piece of sheet metal to act as a pot shield. This increases the efficiency of the oven and channels heat around the sides of the pot. Jokes were made about Frank Gehry as we wrapped the shield around the can.

Rocket stoves work better if you insulate the pipe. We used wood ash for this purpose but you could also use vermiculite. The wood ash also sealed up the gaps in our sloppy sheet metal work.

We got the fire going with a small piece of paper and used twigs as fuel.

With the shield in place the stove boiled 8 cups (1.8 liters) of water in around 26 minutes with a surprisingly small amount of fuel.

If I were to build a rocket stove for daily use I’d want a larger pipe and can to enable burning larger pieces of wood. Another option would be to cast a stove out of refractory cement. I’ve built a similar rocket stove out of a five gallon bucket, but metal five gallon buckets are harder to find. I’ve also used bricks to make a rocket stove. If you know how to weld a world of other design options are open to you.

Do you have a favorite rocket stove design? Leave a comment!