Gary Gilmore is our latest contributor to backyardbiochar.net. Thanks Gary for your words and pictures, presented below, and thanks especially for the drawing that will help others fabricate their own versions of this kiln.
There are four pieces made from 1/8” (11 gauge) mild steel. The top is three feet wide, each piece is two feet high and the bottom is one foot wide. Each piece is identical and has a flange with bolt holes. The battery powered drill gives a sense of scale and facilitates screwing it together.
by Gary Gilmore
Last year I cut the end off an old tank that was four feet in diameter. When laid flat the sides extended up about a foot. A chain was attached to it for the tractor to drag it around to where the brush piles awaited to be made into charcoal. The process is simple. Start a fire in the big fire ring and keep adding brush. As the wood burns, it turns to charcoal which falls to the bottom. More wood is added over this to prevent oxygen from getting to the hot coals. After several hours of adding brush, the fire ring is full of charcoal which is extinguished with water.
A somewhat similar arrangement is posted on the Green your head website run by Kelpie Wilson of Oregon. It is called a Japanese cone kiln which is tapered. This was a better design than the end of an old tank because the sides were sloped. This helped radiate heat back up and funneled charcoal to the bottom more quickly so it would not burn up.
While thinking about the logistics of cutting and rolling a cone, Kelpie came up with four sided pyramid shaped kiln that gave good results. The logistics of working flat steel suddenly became easier. This design was welded together but got me thinking about a slight change to allow it to be bolted together. With a pyramid kiln that can be bolted together you can easily ship it and disassemble it for storage.
Here are some photos of my changes to the Wilson pyramid kiln.
A closer look at the bolting flanges and the top flange. There is a possibility this kiln can warp if it gets red hot. If that were the case, it will be necessary to keep it bolted together. Howerver, there is a chance this may not happen. Time will tell.