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double chamber cob oven - plans

 
Cassie Langstraat
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this is the official thread for double chamber cob ovens.

Get the plans these here(they are made by rocket stove experts ernie and erica wisner)

Get the plans plus heaps of other plans and stuff as part of a mega package here.


here's paul's video of them:



I'm just gonna copy and paste what paul wrote in the youtube description because i think it's important:

Due to huge demand, Ernie and Erica drew up detailed plans for this a couple of years ago.

Ernie Wisner shows off his double chamber cob oven which burns cleaner than a conventional cob oven. The second chamber is what gives the cleaner burn. And your cob oven ends up looking nicer too (not all black in the front).

This cob oven uses some of the stuff from rocket mass heaters (or rocket stoves) for a cleaner burn. Ernie explains why this is not a "rocket cob oven".

A part that I edited out is where Ernie talked about sitting outside around the fire in a way where people stay warm and enjoy a fire without getting smoke in your face.

This video has pictures of other cob ovens and addresses some of the concerns about smoke and wasting of heat. Ernie explains how you start off with a two hour fire and end up with eight hours of cooking: starting with pizza, then moving on to breads, roasts, soups, rice, beans and then yogurt and granola which cook at much lower temperatures.

Ernies also talks about the quality of bread from a cob oven vs. the quality of bread from a conventional oven.

Ernie addresses how he elected to not have a permanent roof over his cob oven.

Ernie's friend Kiko Denzer has a book on cob ovens that talks about this technique.

This video shows a huge flame coming out of the top.


you can get design plans for these here (they are made by rocket stove experts ernie and erica wisner)

Get the plans plus heaps of other plans and stuff as part of a mega package here.


Then, from another thread on permies, here are some other ovens that were built using these general plans:














and then here is a lil preview of the plans:




you can get design plans for these here(they are made by rocket stove experts ernie and erica wisner)

Get the plans plus heaps of other plans and stuff as part of a mega package here.
 
Erica Wisner
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These ovens make a great central focus for very fun pizza parties.
The clean burn is not just the second chamber, but the proportions Ernie and Kiko worked out for how tall the opening is between the two chambers, how big an air-hole goes in the fire door, and the insulation behind the dense baking ceiling. The right proportions help send the flames on a long, rolling path, burning more of the fuel before it exits, yet still preserves the baking qualities of a traditional dome oven. You can vary the dome height a bit, for more of a pizza oven (flatter) vs. a bread oven (rounder), as long as the proportions stay the same.

Below: One of our workshop hosts invited a 3rd-generation pizza baker from a local Italian restaurant. He told us about the wood-fired oven his grandfather built (using stones for extra thermal mass), and brought a big bucket of slightly-too-old pizza dough so we could practice tossing without worrying about dropping it on the ground. (We had other dough already made up fresh for our own consumption).
This particular party was part of Portland's Village Building Convergence, so the crowd was mostly young adults, with a few neighborhood kids. But there doesn't seem to be any limit on who will show up if you start baking pizza. We've done parties with the in-laws, school kids, or just about anybody. When Ernie was baking at Cob Cottage Co, he would make quadruple the dough compared to how many people were on site at the beginning of the day - for example if he was baking for a 15-person workshop, by the time the pizza was ready there would somehow be about 50 people on site ready to eat. Decorate-your-own-pizza preparation tables help a lot with that kind of crowd. But he'd have the oven piping hot, so it could turn out a thin-crust pizza every 4 minutes or so.

Thermal mass ovens are most efficient when heavily used: for longer baking sessions, and ideally every day, so yesterday's heat is still available for use.
If you are interested in shorter baking sessions or once-a-week or less, I believe the plans mention how you can reduce the thermal mass to 1" or 2", and increase the insulation thickness, for better fuel efficiency.

-Erica
IMG_3724-Pizza-Mentoring-600px.JPG
[Thumbnail for IMG_3724-Pizza-Mentoring-600px.JPG]
Pizza mentoring with a local 3rd generation baker
IMG_3727-Pizza-toss-600px.JPG
[Thumbnail for IMG_3727-Pizza-toss-600px.JPG]
 
John McDoodle
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There is definately some artistic stuff here. I love the frog and the snail. Good stuff
 
Nancy Watkins
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Location: Pomezia, Italy
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I was excited to buy this book as I have a rather intriguing possibility: reactive an old communal beehive oven in a medieval hill town in Italy!

The oven is part of my house, specifically it is in the cantina, located directly under my living room. The oven is big, around 8 feet deep and was used regularly until about 40 years ago. The firebrick in pretty good condition, chimney is stone and extends two stories up, past the roof line and has excellent draw (probably too much).

Challenges and changes I am contemplating:

1) The biggest issue is that the oven isn't directly connected to the chimney so just like the usual cob stove, smoke comes out the bread door and can fill the cantina and house. It does however have an area in front of the bread door that I could turn into a small first chamber and add a burn door. The chimney entrance is high up near the ceiling but right there so I imagine the smoke could be channeled fairly easily with the two chamber design.

2) When the oven is cooking, the whole house cooks - not so great summertime! I imagine I can just use the existing structure as my "brick layer" and simply add a good layer of insulation (perlite + clay).

Any comments, pointers, anyone who has attempted a similar project?

Thanks,
Romana
 
Glenn Herbert
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8' deep is really huge! It sounds like it could easily bake all the bread for an entire village. Do you see a chance of actually using the full size of this? If not, I think it would be inefficient to heat it all up to use half or a quarter of the floor. I might consider modifying it to make the baking chamber shorter and converting the front portion to the reburn chamber connected to the chimney.You could probably even do it without significantly altering the existing except for a hole for the chimney, mostly adding new lining.

Is the exterior of the oven exposed so that you could add perlite-clay to it? I expect that would make a lot of difference to comfort.
 
Glenn Herbert
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Another approach if you don't think you can properly use the whole existing size of the oven would be to do all the modification on the inside, adding a good layer of perlite-clay and a new brick liner shaped into two chambers. This would be a lot trickier and probably more expensive, but you could get a perfect interior profile for the reduced size and keep the existing exterior appearance. I might approach that by building up the new brick liner a few courses at a time and stuffing the cavity between that and the original with perlite-clay.
 
Nancy Watkins
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Glenn Herbert wrote:8' deep is really huge! It sounds like it could easily bake all the bread for an entire village. Do you see a chance of actually using the full size of this? If not, I think it would be inefficient to heat it all up to use half or a quarter of the floor. I might consider modifying it to make the baking chamber shorter and converting the front portion to the reburn chamber connected to the chimney.You could probably even do it without significantly altering the existing except for a hole for the chimney, mostly adding new lining.

Is the exterior of the oven exposed so that you could add perlite-clay to it? I expect that would make a lot of difference to comfort.


The plan is for the oven to serve the whole town and beyond! Lots of bread, cookies, but also pizza. To give you an idea, the baker interested currently has a commercial enterprize that does 2000 of the big 5 pound loaves of bread a day. I imagine if she fired it up she would use the oven for several hundred of them plus pizza and other baking. Some years ago it was used to make something like 800 pizzas for a special (one day) event!

The oven is part of the stone walls of the house on two sides but the top can be accessed from one side. I agree a nice layer of insulation would make a lot of difference both in comfort and the amount of wood necessary. My main concern is smoke pollution.
 
Glenn Herbert
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Well, if you have a plan to fully use the beast, great! Then I think your idea is probably the best way to handle it. Pile on the insulation wherever you can reach on the dome.

Ernie or Erica would be the best ones to comment on technical aspects of scaling their oven design up to get the reburn and minimize smoke.
 
scott romack
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This looks pretty cool but, why don't you put a feed tube in the back to the burn chamber?
This could double as the air intake and could self feed?

I'm thinking of a pizza party where you want to 800 deg. to be there for several hours..
 
Acetylsalicylic acid is aspirin. This could be handy too:
The stocking stuffer game for all your Permaculture companions
http://www.FoodForestCardGame.com
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