Sunday, January 6, 2008

Rocket Fuel

Today, we made a rocket stove…similar to a wood stove, but cheaper and more efficient.

It’s a simple underused concept. We made ours with a 25 gallon barrel, and some stove pipe. The barrel we found at Don’s place. It was on old army barrel used to store emergency supplies. The only parts we purchased, were the stove pipes. We used three of them, each costing $7. We thought about looking for free ones, but they usually contain paint, which would have to be burned off...a nasty process.

Emile had built a couple of rocket stove in Portland, so he knew the basic formula, but he also brushed up on his skills from a book I picked up from the Natural Building Colloquium in Kerrville. Leslie Jackson, one of the co-authors of “Rocket Mass Heaters”, graciously gave me a copy in exchange for a CD.

The stove took us under an hour to make. We borrowed Don’s metal cutting tool. That made it a whole lot easier than using our teeth.

We purchased the stove pipe at the right diameter for the feed tube ( 6 inches ). We used the same size pipe for the exhaust tube, but overlapped it on itself to make that diameter 4 inches. We joined two of these together for the exhaust pipe.

Next, Emile traced the pipe diameters onto the top of the barrel to prepare for the metal incisions…one for the feed pipe and one for the exhaust pipe. We then cut a circular opening into the top of the barrel like a shark tooth pie (the cut can be started by hammering a nail into the center of the circle a few times). We bent the teeth on the opening for the feed tube inward, and bent the teeth on the exhaust tube outward. The teeth help to keep the pipes in place while also help to direct the heat flow. The bottom of the feed tube must be several inches above the bottom of the barrel to allow for air flow, which is important when you want a fire. The smaller diameter tubes snap together and then snap onto the barrel.

That’s it.

Starting a rocket stove is much like starting a campfire. Start with paper, or dry grass…then add kindling…and then the larger pieces of wood…all through the feed tube. Once the exhaust pipe gets hot, a draft is created…. making the stove roar with heat while directing any smoke out of the exhaust pipe.

We spent about 30 minutes gathering wood and kindling. Most of the creasote trees ( more like shrubs around here ) have a bunch of dead branches on them. Using this wood prunes the trees while at the same time provides the perfect size wood pieces for feeding into the feed tube. In just a short time, the stove got so hot, that the metal started glowing red. Cover this with a little cob and you got some great thermal mass to heat up an enclosed space quickly.

The idea behind a rocket stove is to use the least amount of wood necessary to create a very hot fire, while storing the most amount of heat as possible with thermal mass. They are much more efficient than a fireplace and even more efficient than a wood stove.


Carpenter John said...

Now THAT is a beautiful thing Trevor!

I am ever amazed
and educated


Dana said...

I enjoyed reading your blog and I learned an awful lot!!