Rocket mass heater system with cookstove

Current design: Works OK but deteriorating and needs to be moved closer to the wall. Easy to load with full-size wood, stovepipe temps 2-300  degrees, no smoke. Cooking features are OK, but not optimal.  Thermal mass inadequate to hold heat.  House is large but well insulated, full-size wood is a requirement.

Tried to insert picture here...not sure it will work.


Replacement ideas:

Pebble Style RMH- love the fact that you can experiment and change it easily. Also, think it might have possibilities to add a "spa" component.  Maybe have different sections filled with different materials, salt, clay pellets, stones, etc. Or trays to switch out as desired.  A constantly available hot rock foot massage sounds like a possibility.

Walker stove- Love the design but cost for materials in my area (insulated bricks) would be prohibitive.

Window preferred to see the fire.

Water heating would be an awesome added bonus as the house has a Pex radiant floor throughout.  We no longer use it much as I found even with 6 zones, it didn't balance exactly as I wished with fewer rooms currently in use.

Easily available materials:

1. Mealmaster cookstove...interested in adding it into the system, cause it is cool and available.


    2.Clay, wool- got them both on this farm.

1. Bricks and other typical recycled construction materials.
2. We have a couple of older wood stoves that maybe could have parts recycled from...doors?


We have a 10' x 10' corner to work with, the chimney pipe is about a foot off the corner.  We considered coming up with some sort of damper, shunting the heat either to the stove or a rock bed with the RMH in the middle.  Or go through the stove first and then to the rock bed. Don't really need to bleed off heat from a barrel if we went through the stove. So maybe replace the barrel with an insulated mass?

Questions...what temps are we looking at where?  How hot is optimal (safe) coming into the stove?   Would there be enough left to heat a box of rocks or should it come after some mass bleed-off, so as not to damage the stove?

Our current firewood supply contains an endless  supply of bark flats, (not sure the real name, but the bark and about an inch of wood.)

I have a feeling the range retrofit idea would not be able to provide enough heat for the whole house, and it would not be likely to allow the use of full size stove wood. It certainly gives ideas for using the heat generated for cooking, though.

I would want to know how good the natural draft of the current system is before giving definite advice. Is it easy to light when cold, or do you need to assist the draft until it warms up?

If the draft is good, a mass bell over the heat riser with its outlet going to the stove might work. You would probably want the smallest bell volume reasonable in order to get more direct heat to the stove, and it is possible that you just need heat right in the stove to work really well.

A batch box might be the best system for using full size stove wood, especially if you have a 6" system. My 7 1/2" J-tube system can use decent size wood effectively, but not as big as commercial firewood tends to be.

Glen, i was just showing this to provide ideas. Not definite answers.

Mass bell over the riser, ok, but with a door and a refractory shelf, to use as an oven.

A batch box with a cast iron plate on top.



Something along the lines of this one, or the previous one.

https://permies.com/t/38889/Firebrick-riser-Esteban#528517

The draft is really good in the current heater.  If you look carefully you will see there are circular plates on the Mealmaster, kind of in the middle.  I am thinking we could possibly run the flue gasses from the RMH into the one in the back, and keep the stove intact.  Not the best looking solution, but easily undone without sacrificing the stove if it doesn't work.  Also maybe insulate some of the surface area if needed.  I think I will just have to experiment to see what will work. It is still in the 80's here, so not yet. But we need a plan for when the time is upon us.  The batch box with a cast iron plate is a simple and elegant solution, similar to what I did with the current cast iron pot.  I love the sketch-ups. I wish I was as adept at using the program to put my pieces together and visualize the possibilities.  

Talk about procrastination....
Well four years later, my poor heater has broken apart and "temporarily" been replaced by the old woodstove.  DH has had some health issues and we no longer have a working tractor.  I hate it.  Besides the increased wood use, I really hate having to wrestle wood into it. Somehow that old heater worked perfectly without smoking even with the front open like I pictured.  When we first built it, we covered the entrance, but discovered it wasn't needed.

But I really want a 2.0 version back.  Red clay is not my style and really doesn't go with the theme of the rest of the house which is more industrial. And while I love the idea of earth building  I honestly hated the appearance.
In my minds eye, I see a  Gabion style RMH perhaps filled with pea gravel or whatever on the inside to facilitate burying cooking pots to slow cook or something along those lines.

Kind of imagine a marriage of the heater I had before, the pebble style RMH and the image I will try to attach.
I like the "look" of it. Gabion things often aren't completely filled they just make the "walls" out of the cages of rocks and fill the center with something else.  
I am guessing I need to build the heater core out of fire bricks and/or refractory cement?   We used regular bricks for the riser of the last stove and they seem to work just fine. Any reason I shouldn't reuse what seemed to work?  

Reading through some comments on pebble-style RMHs, I see the pebbles are considered insulative or at least not very good thermal mass. I didn't really have lots of thermal mass before. But could you "fill the box" with just plain old red clay soil?  Just shovel it in "as is"?  Then maybe I could finish the tops with my rocks and pebbles or whatever.

Hi Carrie;
Short answer is) Yes you can just shovel it in!
Longer answer is Fill with as much large rock as you can...
Shovel local clay/dirt in between as you fill leaving no air spaces.
Sort of a rock /dirt lasagna...