Building a Rocket Stove: Part 1: Stove Materials

by ziggy on April 13, 2009 -- 10 comments -- Follow

A few days ago, I finally began building my rocket stove. A rocket stove is a high efficiency, low cost type of homemade mass heater. The advantage with rocket stoves is being able to run the stove pipe through cob furniture such as benches or beds. Instead of sending the stove pipe straight through the roof (along with the heat) as is typical in conventional wood stoves, most of the heat can be captured in the cob thermal mass. Rocket stoves typically burn way less wood than typical wood stoves, and you can make them out of recycled and salvaged materials that are pretty widely available.

I recommend checking out Leslie Jackson and Ianto Evans’ rocket stove book, Rocket Mass Heaters for technical discussions and instructions for building your own.

Anyway, The rocket stove I am building will have a flue pipe that runs through a cob bed and bench, where heat will be stored over long periods of time, and make for very comfortable sleeping and sitting surfaces. (Direct heat feels way better than just warm air.)

Here is a list of my rocket stove building materials:

  • 69 firebricks
  • 55 gallon steel drum
  • corrugated steel
  • perlite and wood ash (for insulation)
  • cob (sand, clay, straw)
  • 6″ galvanized stove pipe (various lengths)

rocketstove-09brickwork.jpg

Essentially, the guts of a rocket stove is a J-shaped brick assembly, all carefully proportioned so that the stove can actually draw properly. The heat riser, which acts as a chimney, is probably the most important part, and in the case of my stove, is constructed with firebrick, some recycled corrugated steel, and a 55 gallon drum. I insulated it with a mix of perlite and wood ash.

The most expensive part of a rocket stove is the flue pipe, especially in the case of my design, which has almost 30 feet of run. I spent about $200 on 6″ galvanized pipe.

I traded for the perlite and found a barrel and corrugated steel for free, and purchased used firebricks for $1 a piece from friends at Sandhill Farm. I estimate the cost of the stove to be less than $300.

Firebrick is the top choice for building the guts of a rocket stove due to the extreme temperatures it can resist without wear. Eventually all bricks fall apart, but firebrick is built to withstand a lot of high heat.

The 55 gallon drum I am using is pretty run of the mill. Before using any steel drum, you must burn the paint off of it. I built a fire inside the barrel that I kept going for at least an hour, and then I rolled it in a fire pit. I think you could get by with just burning the inside. Afterwards, I used a wet towel and steel wool to wash the paint off, and then I used sandpaper to smooth it out.

In my next rocket stoves write-up, I’ll begin to detail the construction of the brickwork with plenty of pictures.

Here’s a video describing how a rocket stove works:

Check this out for how to make your own rocket cook stove: How To Build a Rocket Stove: 5 Plans

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Célia April 14, 2009 at 3:07 am

I loved your blog! Can’t wait to see your house finished!
Célia

Jason November 7, 2009 at 12:55 pm

Hello, I had a question about cleaning the flue. How do you clean it if it’s making twists and turns for warming benches and such? Or maybe I’m not understanding how the bench was warmed in the video?

ziggy November 8, 2009 at 10:21 pm

Jason: I’ve got three t-joints in the flue so that I can access the innards to clean the pipe. One is at the very beginning of the pipe, and the other two are at each 180 degree turn. Hopefully this will be sufficient to get in there and clean.

jay December 4, 2009 at 1:14 am

Not to be paranoid but, what about creosote? And, what about leaks in the joints.

ziggy December 8, 2009 at 3:26 pm

The pipe is embedded in the cob, so there shouldn’t really be any leaks… as for creosote, the stove is very clean burning, so there shouldn’t be much build-up. But I should be able to clean out the stove through the t-joints when I do need to do that.

Elliot Hallmark February 27, 2010 at 8:38 pm

hey there.

$1 a brick is pretty awesome. My acquaintance is wanting to build a BBQ pit and bricks make the thing REALLY expensive.

There is a technique, or family of techniques, for making cob/adobe strong enough for the fire box of this thing. I am studying it myself (and trying to raise a little money for the cause).

the techniques are related to or are a member of geopolymerization. The only “exotic” component is sodium hydroxide, which can reasonably be made from natural ingredients itself, depending on the geology of the area.

http://www.permafacture.org/geopolymer.html
(contact info for me on that site)

I am trying to raise money here: http://www.kickstarter.com/projects/410996349/making-geopolymer-technology-accessible

thanks!
-elliot

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