Michael Mroz

Keeping the thread alive with yet another question!

Looking at the batch box 6inch system dimensions as an example (8 10 /16 box width, 12 15/16 height, 17  4/16 depth), would the modification/ increase of width by 10-15% impact the performance in any negative way? Has anyone tinkered with the proportions to a tolerable extent?

The Wife is lobbying for a wider glass door to better resemble a fireplace insert for aesthetics, thus the question :]
I`m actually planning to do a 7 or 8 inch build, but the question is just about the proportions.

Merry Christmas to you all Permies!

Hi builders!

Kirk "Donkey" says he uses neolithic materials for the burn chamber in his batch box "Tiny House Rocket Mass Heater" https://www.youtube.com/watch?v=U7kqu1XvsXY&t=5s that is crushed fire brick, wood ash, cow dung and clay. Does anyone know the proportions he used?

Also, are there any proportions that should be maintained in terms of mass of his stratification bell vs the burn chamber or riser diameter?

Any help appreciated!

Hi Permies,

I`m not sure I should post in this thread however the question is related to cob.

A while ago I came across Carl Boehm`s build of a rocket https://www.youtube.com/watch?v=Oh47Jk3I7AU&list=PL9TTdzWoNjzd8_OVJSJlm2UAhTd_m_Ec1&index=1 and his solution of using materials (angle iron, superwool, fire brick + concrete slab) to construct the bell (12min 45sec into the video).

I`m comparing this solution to one I came across watching a Polish builder https://www.youtube.com/watch?v=S80JytfptFs&t=1965s who basically swapped the fire brick with cob (32min 10sec into the video). Instead of covering this with the concrete slab like in Carl`s build, he then covered with fire brick. The whole stove was later plastered. Would anyone be able to assess the durability of cob + fire brick right above the riser and if this would hold up against time and if there are any significant limitations?

Appreciate any feedback.

All clear. Thank you!

So I understand the fire bricks are just loosely stacked against each other tightly without mortar or adhesive and the cob keeps the structure together. Am I correct?

Thanks

Benjamin, thank you. Makes sense keeping the caveat you mentioned.

Going further, I wonder if using loose sifted wood ash placed in between the brick core and cob shell whilst progressing with every lift of cob would work just as well.

Cob behaves differently than fire brick when heated and cooled. How do you prevent cracking and deformation if the inner fire brick core and outer cob shell are joint together forming "one solid rock"? I don't see an expansion gap being used in this build.

I see the benefit of cob holding the core structure together, but what about this method holding up after several heating and cooling cycles?

Appreciate your feedback permies!