One of the hobbies I share with my Dad is rocket-mass heaters. It's a good excuse to play with fire and mud at the same time.
Anyhow, I've read a few things in the news about the EPA dropping the hammer on wood-burners. So I wanted to do something. I've been working on
this for the last month or so. You guys will have to forgive my photography. I'm just throwing this out there for anybody who is into this sort of
This was our second rocket-mass. It was made out of a 25 gallon drum, and a 35 gallon drum. It lasted a little over two years, but was about to burn
out. We wanted to rebuild it before the core and riser dropped.
Here you can see just how badly the core and riser were leaning. It was a good heater. We carved it out of the dirt as we worked on the man-cave.
It served it's purpose.
After demolition, we see just how burned out the burn-box actually is. Wow.
We left the pad, and the original exhaust box in place to keep from having to manufacture a new one. This heater is temporary as Dad and I will build
a more ornate and functional version in the man-cave.
To my surprise, The original core was in pretty good shape. The internal stove pipe had incinerated, but the clay held up very well. You make a core
by starting with stove pipe, then get some metal flashing and wrap it into a tube. Use bailing wire to size and secure it to about 1.5 to 2 inches
larger in diameter than the stove pipe. Then fill the gap with clay and allow it to dry somewhat. I don't have pics of that process here as we
reused the original core with a new stove-pipe insert.
Here is where the Wood-Burner comes in. This thing has been a yard ornament for the last couple years with us. I think it was a yard ornament for a
couple decades with the previous owner.
We took the legs off and set it on the pad where the previous burn-box had rested. We will use the exhaust port to be the inlet to the combustion
chamber. We dry-stacked some reclaimed fire-bricks to make the transition and base for the core and riser.
Here is a top view. You see the inlet for the exhaust box and the new stove-pipe insert for the core.
Then we mixed a batch of cob. Just clay, sand. straw and water. Make it to a workable consistency. If it gets runny, add more material.
Now for the fun as we mud in the transition and place the core on it's new burn-box.
More mud fun. You want to make sure to get the mud worked into the gaps as well as you can to give a good seal.
Then we covered the core with the combustion chamber/riser and added mud around the seams to make sure it was a good seal. Then we lit a fire and
started the burn-in. The transition has to be completely closed off or the burn box won't draft properly, and your man-cave will fill with smoke
I let it burn for an hour or at this stage, and went for a snack. I wanted the mud to dry enough to start adding mass around the burn box. I used
reclaimed brick for filler to speed up the process of adding mass. We will have to demo this someday and move it to its final resting place in the
In this picture I had made more cob, stacked cob and bricks and extended the mass from the transition to the front of the burn-box. I also added a
layer of cob to the top of the burn-box. Then I let that burn for an hour or so.
Then I cam back and stood two bricks on end and covered them with mud to bring the mass all the way to the door. Dad and I did this all over the
course of a day.
The next day we added a layer of cob to the exhaust box.
The next weekend I made a huge batch of cob and added a layer to tie the whole thing together. Thick layers crack. So I just make each finishing
layer thinner and thinner to work into the imperfections and smooth everything out.
And there ya have it. It has been a fun project, but the whole man-cave is a fun project.
There are a number of you-tube videos out there that show you how to build these things. Some people are really into it and get straight scientific
to reach peak efficiency and all of that. Good on them. This one probably isn't the most efficient, due to it's size and drafting characteristics.
I can assure you that it is much more efficient than the wood-burner would be on it's own. With the 6-8 inches of mass around the box, we can burn a
fire for about 3 hours in this thing and get about 8-10 hours of heat out of it. The riser itself probably puts off about 900 degrees or more. It
does glow red. It does smoke for the first 10 or 15 minutes when you initially start a fire. Once the rocket effect starts, it emits mainly water
Hope somebody can use this information and do something for themselves.
Have fun with it, and stay warm.