Glenn Herbert wrote:For in-depth development and construction info, see Peter van den Berg's posts at donkey32.proboards.com, and also Matt Walker's. The Reference section has detailed info.
By the way, it is typically stated that a 6" batch box can give heat output generally seen with an 8" system. Matt Walker converted his 8" J-tube system to use a 6" batch box and reports that it works excellently.
Brett Andrzejewski wrote:I'm glad you enjoyed the RMH class.
Please look at the two examples in the following links: 8" batch box
Innovators batch box. The pictures about 11 posts down help illustrate. It is close to the dimensions you seek.
Yet, notice how tall the heat riser needs to be to maintain the a ratio of around (1:2:4). In the first example it is two barrels tall.
michael Egan wrote:hi Peter
I just posted a reply on another thread earlier today so some of what i say here is repeating what i said there: I build two vertical feed rocket mass heaters and was not getting enough btus to heat my 34x30' shop so i built a batch rmh and love it. it will take a 36 in. log about 7 in diameter, about 30lbs of wood at a time. This is my 3rd heating season with it. Here's a link to the video i did in March 2013, almost a couple of years ago.