It's been a full summer. Lots of projects going on around here! Among them, my natural building apprentices spent a LOT of time experimenting with rocket stoves for cooking. Over the course of the last couple of months, we've built an outdoor cooking complex.
First, we fixed up a small but traditional wood fired, beehive oven. Then, after using that for a time, we built a double ended stove (2 rocket stoves) for boiling/frying.
This is early on in it's development. 2 rocket stoves, the one on the left began as an Aprovecho-style, horizontal feed; the one on the right, a J-tube rocket. Later, the horizontal feed was modified into a J-tube as well.
Here is roughly how the internal channels go.. Notice that there's no chimney here, you can cook/heat food on ANY port up on top. For exhaust to flow out, one of the ports has to remain open; we often placed a chimney over one of the cook-top plates and cooked on everything else (simultaneously).
This middle(ish) cook-port got remade into a deep pot heater with a combination chimney, chopped into the side (and a tea-cup warmer added).
Yep.. We ARE using coffee cans as a chimney. Works just fine, so far! Oh, and yes.. Both stoves vent through the one chimney.
notice how the pots sit deep into each "pot well", this maximises heat getting into the pots. Other cook surfaces can be used as well.
After much experimentation, a few changes and some decorations later, this stove is functional and beautiful.
Besides the coffee cans, is the entire build cob? I see what looks like firebrick in the pictures.
What you see are adobes, which are basically cob popped out of a brick form and allowed to dry before use. I LOVE using adobes, they take time to prepare but REALLY speed things along on build-day!
The whole thing is made out of cob/adobe. The fire(s) are insulated with perlite/clay, which is the only bagged/ready-made product in the works. We are using a couple of old fire-bricks on the feed openings to meter the air..
After building the pot cooker, the next logical step in our experimentation time was to try to build a rocket powered baking oven.. So..
First, the stand with rocket core. We had to tilt the heat riser to get it centered in the oven base.
We made a couple of different options for heat path. One option is straight through the center, this can be plugged which will send heat through eight little channels that pass under the baking floor. These channels were built by cobbing over a tomato paste can and carefully slipping it out while working.
Then we temporarily plugged the holes and built the oven on top.
It worked great and produced excess heat, so it was decided to add a double-boiler hot water system.. Notice that the exhaust to the water heater comes from the bottom of the oven and drops down quite a bit before going 'round the water pot.
The double boiler system.. An open pot (of water) is heated directly and has a copper coil in which is pressurized. The pressurized coil has a higher boiling temperature than the open pot and will NEVER be dangerous. It also has the curious ability to provide MORE hot water than the volume of the pot being heated (at a reduced temperature certainly, but still quite hot).. Pretty neat trick!
Then of course, our very artistic apprentices decorated.
Very beautiful! And, then there was PIZZA!
The digital thermometer in this image shows 388 F. Just to point out that the oven can get up in the 600 F range for cooking pizza.
Ronyon, I made a metal door, is it not in the images somewhere? Without the door in place, the water heater gets no heat..
Interestingly, this oven works in reverse to the traditional wood fired, pizza ovens.. Here, the heat builds AS you cook, with foods that cook at cooler temperatures going in first and higher temperature cooking happening later.. Normally, it's the other way around.
The oven has a layer of perlite/clay as insulation.
There is NOT a protective coat on these.. I need to build a roof before it rains.
How long does it take for the plain cob rocket oven, without a boiler, to reach temp?
The boiler has ZERO effect on how hot the oven gets.. The boiler gets its heat AFTER it's run through the oven, a reuse of the oven's waste.
Depends on what you want to cook.. Granola wants a low temp and you can start cooking it pretty much right away.. Pizza needs high temps, which takes an hour or more of firing. A very nice feature of this stove is that you can keep on firing it as you cook..
Thanks for the responses Donkey!My wife is totally loving these cookers, and she wanted to know if you used a trench around the structures or a stone foundation, to avoid ground water wicking issues. Both of us are amazed and preserving the coolness is on our minds.
With all my posts, please keep in mind I have one cheek still firmly in the armchair...
No trench.. Just urbanite (broken sidewalk) on the ground as a moisture-break and cob on that. It seems prudent to build a higher foundation than we did. I expect some water damage down low from splash. These cookers were not originally meant to be permanent, they started out life as experimental "kick-overs". Things kinda got out of hand and now, i've got to figure out how to protect them.. They're too nice to just let go to hell..
dan1941300: If possible in metric cm, how many Celsius at the chimney? Is there anything you would do different if building again? Sorry for my bad english, my language is german, austrian. thx a lot
May 11, 2018 9:38:02 GMT -8
smarty: Dan my batchbox reached 1150C so refractory cement rated to at least 1200C
May 21, 2018 22:53:56 GMT -8
mercedes: Not sure where this question will end up...I just registered. HOW THICK SHOULD PERLITE/VERMICULATE/CLAY INSULATION BE BEHIND THE THERMAL BATTERY/COB BENCH IF IT BACKS UP TO A STRAW BALE WALL? Thanks! Can you please also post me: email@example.com thnx!!
May 28, 2018 20:05:23 GMT -8
kkp: Mercedes: Benches don't get real hot. In fact, they are rather cool compared to other areas. You shouldn't need a mix like you described
Jun 7, 2018 18:10:52 GMT -8
maartenmartens: beste Peter, ik heb je eergisteren een mail gestuurd via het contact formulier op je website , heb je die goed ontvangen ? mvg Maarten Martens, architect - geobioloog (mail betreffende de bouw van onze eigen RMH)
Jun 20, 2018 13:21:57 GMT -8
martinm: any one here with info \ experience with heat (from a mass heater) distribution with ducts throughout two storey house ?
Sept 8, 2018 22:58:52 GMT -8
padica: Good morning, this is a wonderful subject, please someone can help me with the theme of double and triple combustion, how it is achieved, theory and design, thank you
Sept 15, 2018 7:13:40 GMT -8
wiscojames: I'm afraid you won't get a response to such a vague question - I suggest reading through some of the threads related to your questions before asking for an explanation. People will be very generous with their knowledge if your question is more specific.
Sept 18, 2018 4:48:00 GMT -8
daniel: in my experience as I am working now on something of that nature, I have thought of making a heat exchanger and distributing the heat through vents using a slower fan. Now after a few years I realize that mass heaters give out primarily radiant heat, for
Nov 30, 2018 12:48:38 GMT -8
coastalrocketeer: Anyone posting in this shout box... if you have something you want people to see and respond to, create a thread in the appropriate forum section... this is not the place...
Dec 16, 2018 18:10:49 GMT -8
vesuvius: High Temperature Glass options,
Jan 4, 2019 16:28:17 GMT -8
vesuvius: Do any of you have experience with using the glass from home oven doors on a rocket stove? I'd like to have a viewing port on my stove but don't want to fork out for new ceramic glass. Any thought as to whether it would take the heat of a rocket stove?
Jan 4, 2019 16:30:40 GMT -8
yaya: you dont need the blowair for that temp..
Jan 13, 2019 16:43:57 GMT -8
flybywire: Glass window from an old washing machine is designed to take high temps. Cheap solution to your need.
Jan 27, 2019 0:10:58 GMT -8
coastalrocketeer: Anyone posting in this shout box... if you have something you want people to see and respond to, create a thread in the appropriate forum section... this is not the place to have a discussion... it is for short announcements
Feb 7, 2019 0:11:23 GMT -8
coastalrocketeer: you won’t likely get replies to questions here, and it is not a spot that makes holding an ongoing discussion possible...
Feb 7, 2019 0:12:22 GMT -8