Glenn Herbert wrote:I think you have been misled by a lot of youtube videos, which are not made by people who build rocket mass heaters regularly, but by experimenters who are familiar with woodstoves and maybe rocket cooking stoves.
Glenn Herbert wrote:I'm sorry, but you seem to have misunderstood the way a RMH core with the 1:2:4 proportions is supposed to work. The 8" dimension is the vertical wood feed AND air intake; the 16" and 32" dimensions are correct. There is no front air intake. Also, the feed works better completely vertical than slanted.
Glenn Herbert wrote:
If you think that a front access port is needed for ash cleanout, I can assure you that it is not (unless maybe you have gorilla-sized arms). I have cleaned a 6" x 6" J-tube with my bare hand, and with a sardine can on a short handle, easily.
Glenn Herbert wrote:A 5" x 5" core would be trickier, but for a 6" duct size system, a 6" x 6" core would be fine.
Glenn Herbert wrote:Can you give us any information about your plans for the system? What kind of mass, how long, what size of space and how insulated, how you use the space, what your climate is like?
Glenn Herbert wrote:It may be helpful to explain that having the wood feed capped off and air coming from the front will let the wood get hot and char up into the feed tube. When you open the cap to add more wood, you risk a puff of smoke or even flame bursting out of the top and singeing your eyebrows off. The air intake pulling down from the top keeps all the fire and smoke moving in the right direction, and you can clearly see when you need to add more wood.
Glenn Herbert wrote:The 16" burn tunnel dimension is a maximum, and if your barrel clearances allow, you can make it shorter and get better draft.
Glenn Herbert wrote:Keep the feed vertical, though. The best method I have found (also recommended by everybody I have read) is to lean the sticks away from you so that they lean against the burn tunnel roof, and air has to go down on your side of them or through and between them to get to the fire. This keeps the tops of the sticks a bit cooler and helps preheat the air. If you lean the sticks back toward yourself, the air can flow down on the far side of them and leave some of them starved for air, while a lot of air goes into the burn tunnel without meeting the burning coals.