Does anyone have experience or ideas how to integrate a cob oven into a rocket mass heater system?

Hi guys,

Does anyone have experience or ideas how to integrate a cob oven into a rocket mass heater system?
Maybe the best position is above the heat riser, but I would like to use the top of the barrel for cooking..
- Would it be possible to sculpt a small oven over the burn tunnel?
- Or right after the exit flue and 'curl' the first part of the exhaust pipe (under, up & behind) around the oven?

Would it get hot enough to bake a bread, quiche or chicken???
Any theories are welcome before I start putting the house on fire .

Thanks,
Sascha

I'm interested in this also.

My RMH has a small oven off the front of the feed tube. It works great, I cook bread in there everyday. It was an unintentional benefit of the way I configured my door/window on the front, but in hindsight I would build it bigger and put a masonry stove type oven door on it. It gets plenty hot to bake anything you would want. It does take a bit of managing, but with some tinkering and a bigger oven box, I think it could be made to work very, very well for everyday general baking.

You can see it here:

http://www.youtube.com/watch?v=A4NoC0U8geM

Somewhat similar to Matt Walker, we have been building rocket combustion systems that double as masonry ovens up here in Alaska. Our heating needs are pretty great so we have been building more batch style rockets with a horizontal loading front door instead of the downdraft. We have developed a simple plan using firebrick with a masonry arch that creates a nice oven for use after the fire is out and it equalizes similar to a traditional black oven. This way it is not something extra, just a side benefit to the design for more approachable batch load burning. Now after a full season of use with several of these we are refining the design, doing some flue analyzing and we're looking forward to leaning on some of the more experienced rocketeers in the PNW for more testing/input/refinement next month while on tour. We have a goal to make this "kit" or plans available as an affordable option for the do it yourselfers after we are ready in a few months, so stay tuned. I have also played around with the idea of a cob oven downstream from the heatriser and still hold this to be a viable option. In fact, our ash fall out areas right after the barrel have essentially been cob "bell" ovens (we have even bisqued some clay sculptures in them) but they lack the larger door to load with bread etc. Adding an oven door and shaping/adding more mass with the intention of baking would be another great way to go. There are a lot of approaches possible in this oven quest! I look forward to others sharing their experience! Canyon

Well, I've been waiting to post this because it's untested yet (I'm building a test version this summer, so I'll know if it works soon) but since you specifically asked for "ideas"...

It's not a cob oven per se, but the idea is the same. The oven is a brick oven and it sits on top of the heat riser and acts like a bell. The hot gases can flow up into the bell past the edges of the oven floor (made of stone or brick) and hang out there until they cool off enough to go back down. The door will be airtight, and the idea is to fire the RMH for a while, then after the fire goes out do your baking. My big ambition is to cook pizza and bread in my heater this winter. We'll see how the outside version works first though.

The other thing you'll notice is that I'm going to see if I can make it work with a square radiating surface, simply because I like the looks of it better than the barrel system. The brick columns on the corners are there to support the weight of the oven on top, and also for a little decoration.

This is presented with the massive caveat that it's untested and probably won't work as designed, but I hope to have a working setup by this fall and I'll post an update here if I can manage it. Please ignore the random yellow dot, that's an artifact of the program I used to draw the thing (blender).

Another design that some folks have reported good success with is on top of the barrel, but as a temporary 'dome' or dutch-oven type structure.

Ianto's book shows a dome of crumpled aluminum for a very basic oven. Any insulated dome will work OK while the rocket heater is running.

Someone else (it might have been Kiko, or Donkey?) on the research team has built a slightly more permanent oven dome that's still removable.
This was a large terra-cotta pot with insulation, that fit on the barrel top. I believe this had a door opening built into it, and a handle; it could be removed to allow other kinds of cooking on the barrel top.

Sometimes it pays to separate the oven from the stove from the home-heating unit, especially if you like pizza in summer.
Here's a separate pizza-oven design on a rocket stove base that might make a better option for a summer kitchen: http://greenrocketoven.com/

-Erica W

Dear Erica,

Greetings from the Methow, I look forward to meeting you in person as your student on April 28.

I am thinking of putting an insulated box atop my barrel for cooking.

Any input you might have would be appreciated.

I think I've seen you and your husband at either the Twisp Market or at Barter Fair.

Best Regards,

kt

Any insulated box you would use on top of a woodstove, should work even better on a rocket mass heater (it's easier to balance a decent-sized thing on top, for starters).
You can also make a stand-alone oven like this one: http://www.greenrocketoven.com, or try a YouTube search for metal rocket cookstove-based ovens like this one: http://somewhatsketchy.com/?p=115

I did like Matt's little front-end oven, and his Dutch oven also looks like a good option.
I can see the Alaska folks doing something similar. I heard from Donkey that the batch-burn style horizontal feed works nicely.
(Wish you had made it up here, but I'm glad you had a good visit! Once your design proves out, feel free to contact us if you want help selling the plans.)

We are thinking about a similar feed-area oven on a new, tiny cookstove for a boat. If you don't need the oven function to be large, or used very often, it's worth thinking about just using an existing part of the burn chamber as a semi-practical oven space. (Yes, I know, people have been teasing Ernie about a cob boat for years. This is for someone else's boat, thanks very much, and it may just be brick and not even cob.)

I would love to see some more pictures of the 'standard' oven on top of the barrel. We tend to just build an outdoor cob oven, since our previous homes have been in places where there's a surplus of big, knotty wood that won't fit into our rocket heater.

-Erica W
http://www.ErnieAndErica.info

Trick I learned from an old fry cook: use a stainless mixing bowl as a dome lid. I use it to make pizza on the regular cookstove.

A weber lid is a pretty close fit, depending on your barrel.