Post #387964 by Limbo Lizard on Wed, Jun 18, 2008 6:12 PM

On 2008-06-18 18:02, Haole'akamai wrote:
...I guess I was figuring you'd have wood all the way up to the top

MadDogMike described using two washing machine drums in the pipe/hole (that's the ingenious part!). The bottom one holds the wood/coals, so I assumed he only filled it to the top of the drum. You could add wood, as it burns down, if it hasn't heated the surrounding earth enough, yet.
I could be wrong... maybe he does fill it up to the top, then lets it burn down until it's below the top of the lower drum. Mike?
If you have moist clay, you might want to dig it out, somewhat, and surround the pipe with loose sand. The clay would probably shrink away from the pipe, when it heats up and loses water content. Then you'd have a heat-insulating air gap between the pipe and the surrounding earth. The sand would be more 'dynamic', and would conform to the outer wall of the pipe, as the surrounding clay shrinks and swells.

[ Edited by: Limbo Lizard 2008-06-18 18:35 ]