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montagne 11-04-2009 07:20 AM

Light Cob oven
My goal is a portable pizza oven. No need for bread (I hope). I want to build it myself on the cheap. I have experience using cob and I am also looking for the sculptural element that cob can provide. This oven will need to survive transportation but the mode is as yet undetermined. I know I need to maintain 700 degrees and also strive for an efficient wood burn. Correct?
Weight is a major factor when selecting transportation vehicles. How light can I go? Perlite plus cob in the walls and a firebrick floor? How thin can the walls be and still hold enough heat? What about reinforcing against the rigors of travel?
I have many questions and very few answers.
Thanks for any input.

marklewis 03-31-2010 07:31 PM

Re: Light Cob oven
Did you ever build an oven? Clay is OK for a stable location but might not fare well from all the jarring over roads. The lower the dome, the weaker it will be structurally also. I found a good ratio which works for my clay oven (see attached thread).

A trailer could handle the weight; my dried cob mix is lighter than the same volume of fire brick. And yes, 750K can easily be reached and will be easier to achieve when insulated.

You could do some extra engineering to make a clay oven last longer for transportion but If your going to that extra trouble to make it portable you would best be served by making a poured refractory dome or a firebrick dome with embedded wire over the dome's concrete for extra structural strength.

dmun 03-31-2010 07:58 PM

Re: Light Cob oven
You understand that a masonry oven absorbs and reflects heat: The mass of the oven is what makes it work. If you make it from a perlite mixture you won't have the thermal mass to make it work.

And yes, dried, unfired clay will crumble when exposed to vibration.

Archena 03-31-2010 08:18 PM

Re: Light Cob oven
Hmm, it might - and I do mean might - be possible. Good shocks will not be optional. I strongly recommend trying it out a small scale - nothing that won't fit a 16x16 paver (you can go smaller but I think the 16x16 will give you a better representation). Instead of ordinary cob you could try a 'daub and wattle' version using chicken wire as the skeleton. That would give it some more 'flexibility' (too late at night for vocabulary...).

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