Elbow Rocket Stove Number 1

While strolling through the yard at Recycle North's Building Materials Center, I spied some double wall stove pipe. Three pieces were $5; I didn't haggle. This is nice stuff: a heat resistant stainless steel inner liner, suspended inside a galvanized outer wall. There was a good sized pile, with plenty of elbows -- the critical component of a rocket stove.

For the first firing, I found a piece of stainless sheet in a scrap bucket and hammered a fold to make it fit in the pipe as a fuel shelf. Three concrete blocks arranged on end provided a prop for the elbow and a support for the cooking pot, a brick underneath raised the pipe close to the bottom of the pot.

The second firing added a short section of regular stove pipe to lengthen the vertical flue. A few extra bricks were needed to support the cooking pot at the right height. We roasted hot dogs on skewers, made s'mores, pan fried hamburgers and popped popcorn using perhaps 2 kilograms of wood, finely split poplar and some apple branches and twigs. Once the fire was started (using dry leaves and a couple of used paper towels), the fire burned hot and clean. The fire was easy to douse with water.

This photograph shows the onion shaped refractory fireplace that we have used in the past for the same sort of meal. We would have used three or four times as much fuel and it would have taken careful tending to keep the fire going.

This version does a reasonable job of satisfying the Ten Stove Design Principles. Its shortcomings can be resolved: lack of insulationg around the combustion chamber and flue, and uncontrolled flow around the cook pot. I am going to keep this prototype. It is portable, the construction is visible, and it is a significant improvement over the fireplace.
In the next generation based on this double wall elbow, I would replace the flue extension with an integrated pot skirt and make three metal pot supports that would slip onto the liner pipe. The air gap would be filled with perlite or vermiculite, and the whole thing would sit on a bike rim layed horizontally and cobbed together to ballast the stove. Sections of the bike rim would be exposed as carrying handles.

Design Principles for Wood Burning Cook Stoves is a nice reference. Read all about rocket stoves at the Aprovecho Research Center's Publications & Reports. Two videos illustrate the original Aprovecho Rocket Stove and its predecessor, the VITA Stove.

Kids enjoy chasing popcorn popping in an open pan. Note the unpopped kernels and drops of hot oil that are flying out of the pan. We'll take care to use less cooking oil next time.