Another guy and a Pizza cob oven..

it's been about three months now that I have been doing some occasional research on different types of pizza ovens. At this point I can safely say I have read just about every Fred I could find in this forum along with many of the great sides that people have linked to and of course watched tons of YouTube videos.

Because there are so many different ways of building is, the most important stage was defining what exactly I want.
Overview of my aspirations for the oven:
-decently higher temperatures from above and below to make excellent pizza 400°C would be ideal
-Heat retaining qualities to last me at least one round of the baking bread, circa one hour of 200°C
-Because I won't be having many parties catering for 50 people, I don't want to spend hours preheating the oven, maybe 45 minutes would be good. This is also a factor in fuel consumption, I'd like to be able to make a few pizzas and two breads without using tons of wood.
-I don't have welding experience although I could find a friend if necessary, But prefer without.
-I would like to reuse A large 200 L oil drum that I have for the shape and I am hoping to build primarily from cob, Stone and tile debris and rubble and get away with only having to buy the firebricks and some small things if necessary. i have a small amount of cement here aswell.

wisners double chamber:
i have studied the wisners double chamber cob oven in detail and for my purpose it might take too long to heat up and is more suited for frequent use. however it is on my list of possible solutions. they mention the possibility of reducing the outer shell for faster heating but thats coming down from an original 2h heat up time.

traditional pizza oven:
i have studied traditional ovens and their dimensions, which again is fantastic but takes long to heat and is not taking advantage of rocket/reduced fuel possibility.

hybrid rocket cob oven:
then there are the hybrid rocket cob ovens that often have the riser come up right at the center of the hearth, where it seems to me that of the hearth gets too hot, its too cool at the top and the hearth often doesnt withstand the brutal direct heat. they also seem like one of the more challenging builds.

fancy new tech portable pizza ovens like uni 3:
https://youtu.be/YyR5Hbi2iig using part of the rocket principle to draft the flame along the top of the oven and over the pizza and the stone, resulting in high temps above and below in short heat up. downside: unsuited for baking, expensive and my garden doesnt grow pellets.


i'm wishing that you guys, who i can see have vast knowledge and experience with rockets might give me feedback on my plans. my idea is to use a rocket for fuel efficiency as a hybrid or the uni do, but combine it with a not too deep cob insulation to give me the ability to bake. i'm adding a chimney at the front like ernie and the uni to draw smoke out the top and am considering (not sketched) a 2nd bake door like ernies. the deflectors are an idea that came again from uni and from a sketch by satamac.

specific questions:

1 what do you think i can use to line the inside of the drum and even lower the height on the inside with. clearly it needs to be lowered for the design to work. the difficulty there is sctructural, so it doesnt just collapse. could cob work and how could i maybe suspend it?
2 what can i use a binding slur in the base together with rubble, stone, tile and glass debri? cob slurry, cement or a mix?
3 the heat riser will not be insulated with sawdust and ash as in the sketch. i read all about metal in heat risers and its obviously not the way to go for longevity and food safety, so i'm thinking on molding a cob riser or just fire bricking it up.



hugely appreciate your help and criticism, i'm just hoping to finally settle on a design and get started.

cheers brian

So there have been some changes made to the plans, it contains some definite errors.

First of all I am going to use the wet sand method rather than the oil drum for the shape simply because when the oven is heated up the metal expands and I presume Will simply bust the cob around it. Essentially the shape and build will be based on wisners double chamber oven. I am however still interested in keeping the Rocket as designed in the pictures above to draw the flames right across the top of the bake goods in the way the uni does it.

The next question would be whether the cob is structurally capable of supporting its own weight in a much shallower Dome. How much lower do you think I can make the dome than in the original design? Of course with out changing the base dimentions

Brian, have you se en this one?

https://permies.com/t/64821/a/49481/pocket-rocket-pizza-oven.skp?download_attachment=true

Hi Satamax, Thanks a lot!
I had already downloaded your file but not installed the suitable viewer for yet. Just looked at it and looks like a great design, I will certainly incorporate or maybe base my design on that. I suppose you would add a deflector on the inside of the feed tube, like two or three fire breaks. also I am contemplating and oval shape.

Would you just brick the dome? I am not sure my skills would it be good enough to do that. Maybe an inner lining fire cob followed by an inch of cement for Weight bearing structure and then insulated cob around that? That would raise the question of whether cement gases could enter?

Hi Brian.

Bear in mind, that this hasn't been tried.  And most certainly would smoke back when the door is open.

I'm about to draw the same, with a batch rocket. As i think it would be better.

But i think those two are more  suited to pizza cooking, than a J or L shape rocket.

The pocket rocket, for the ease of building, and having the fire in the oven itself.

The batch for it's high power.

I don't get what you mean by deflector in the feed.

By the way, i nicked the original drawing from sketchup's library.

And as for the dome, i think i would do mine in a corbel vault.

For low tech,low cost rocker fired ovens ,check out the work of Flip and Jon Anderson

http://www.rechoroket.com/"How_to"_Albums/"How_to"_Albums.html

They have been doing it for years, but have recently updated their site. Here is the home page:

http://www.rechoroket.com/Home.html


They have even built rocket powered kilns, truly they are low tech innovators.