Peter van den Berg wrote:
Robert Dearborn wrote:One feature im unclear on from the sketches and the podcast - is there a heat riser inside the barrel above the heater ? What is its proportion ? Im assuming it doesnt reach to within 2" of the underside of THAT monster barrel !
Your assumption is spot on, there is a riser inside the barrels. It's reaching up to about 3 to 4 inches below the top of the first one, so the top gap is one barrel plus 3". The riser is an 8" ceramic fiber tube, it could be shorter but it is being used as a whole.
The space around the riser and the firebricks is filled in with a perlite/clay slip in order to fix it in place.
The barrels happened to be open-top types. Ernie adviced to fit the lid around the riser and cut open the bottom end of both the stacked drums. It is even possible to extend the tower with yet another barrel. The gap between the riser and the hole in the lid is stuffed with superwool, of course.
When cutting, one inch of the bottom has been left around the perimeter, this way there's a better chance the barrel would stay circular.
Glenn Herbert wrote:US standard firebricks are 4 1/2" x 9" x 2 1/2" or sometimes 3", so they should almost precisely make up the 17 7/8" height from the chart. I have seen off-brand firebricks with smaller dimensions, maybe 4 1/4" x 8 1/2". Be aware of the possibility if buying firebricks from different sources.