John Elliott wrote:Urban area? How about used bricks? Rather than sculpt your RMH out of cob, if you can score some old solid bricks, you could assemble it LEGO-style. If you want it to be a little more permanent, then you can hold it in place with some refractory mortar (regular mortar with clay added).
posted Yesterday 1:14:30 PM by Allen Lumley in the thread 'Heat riser, duct/flue questions'
...All of the stove pipe buried within the R.M.H. / Thermal bench should be considered to be a sacrificial form around which your cob, your Perlite And Clay Slip are placed and a few bricks are stacked. As such we do not care whether they last weeks or years, here we can go with the cheapest grade of thin wall piping we can find, the lighter the better, galvanized pipe having no inherent advantage!
allen lumley wrote:Matthew Nistco :As the mortar used to assemble the bricks is actually used to hold the bricks (universally ) apart from each other, we can
use a Lime mortar, rather than a Portland cement based mortar. Lime based mortar cleans off of old bricks easily, and holds up to the
Rocket Mass Heaters R.M.H.s, high Temperatures with out failure much better than the Portland.
Again, if you are strongly thinking about a R.M.H. in your future, look at my comment above, and get your copy of Rocket Mass Heaters at