I was reminiscing about days gone-by, when I had
land to play with, before it was taken away by scared people who didn’t understand what kind of stove I was building. . .
Once upon a time I had a pretty cool
cob house about half-built up. It was built around a unique
Rocket Mass Heater which was complete and functioning nicely. I felt the design of this stove had made a significant improvement upon the shoulders of the more traditional
RMH design. But to ruin the end of the story. . . the house was never completed, because we got booted off the land ~ partially because this strange stove design really concerned the fire department when they saw it. I could talk more about this, but the point of this post is to share a possibly considerable improvement for anyone considering building an
RMH.
The RMH is so amazing because it solves so many of the problems that traditional
wood burning comes with. But one problem the standard RMH design hasn’t solved yet has to do with airflow. We know a fire is like an air pump. It needs to have an air intake from somewhere. If, as in the standard design, we take this air from a
feed box in the middle of the room, then the air is secretly being sucked and squeezed through every crack, window or door of the house, drawing cold air through the space. One solution to this is to have the feed tube near the front door. . . this partially solves the problem, but comes with another airflow problem anytime you open a window or door, dramatically changing the airflow, and effecting the fire. . . I even saw this effect frustrating Ianto as he was trying to demonstrate lighting the stove in his home. Plus that’s a very sloppy solution because there’s really still a ton of cold air leaking in from everywhere and spilling from that area between the feed-tube and the door. So…….. I have a semi-tested idea that I’m pretty sure fixes all of this, *evil Wheaton grin. :)
Instead of a feed tube like shaped like a J, I had a situation more like a short upside down T, where one part of the T is going straight through the wall of the house! I had a small metal garbage can with a tight fitting lid and a hole cut through the bottom of it situated along the feed tube at a comfortable human angle (The vertical part of the upside-down T). This way I could comfortably see, feed and tend to the fire from inside like a normal RMH, but as soon as I put the lid back on, the airflow was sealed completely so all air feeding the fire would draw from directly outside the house, no longer creating a negative pressure inside the interior space. Does this make sense??
Another benefit of this system is that there are now two ways to feed the fire. One of them is from just outside the front door, near the outer wall, where there is a very long and straight feed tube directly to the center of the RMH hot-spot. If your zone is anything like ours, we have a ton of long sticks and branches that drop from the
trees every year. It would be nearly effortless (compared to any sort of chopping/splitting/processing) to simply gather these in bundles, put them in a big shed where they would stay dry (I recognize it would not be nearly as space efficient, so this is contingent on having abundant space to play with perhaps), and then simply stuff a couple long sticks through your outside wall and straight into the fire . . . I always wanted to devise some kind of bungee system to apply a little force to the end of these sticks, jutting a few feet out from the wall, so they would automatically press further into the fire as they burned down slowly over a couple of hours perhaps… maybe some sort of a trap door that gravity fell on top of the sticks as they burned and slid inward. . . this would dampen the airflow as the mass of sticks diminished and then seal the warmth in once the final stick was shoved inside the wall by the bungee. . . I never made it to this stage of the tinkering. . .
One feature of this design is that the fire may have been less drawn “down and into itself” like it is in a J tube, where the heat seems most intense on the roof of the tube right before it opens to the heat-riser. . . . In this new design with the straight feed tube (when the lid was tightly closed) the air shot straight through the tube and seemed to hit the back wall more, and send the flames directly up the heat riser. . . The change may have effected airflow inside the burn chamber . . . I’m not sure if it was an improvement or not. I'm not even really sure how different it was, because this is the only RMH I've worked with for an extended time. This is all theory. . . Maybe more heat was going up the riser and into the remix chamber? Or perhaps the wood was not burning as hot in the first place, without the magic turbulence the J-tube introduces from the beginning of the airflow path. . . I’m not sure! . . . . It seemed like it was burning totally awesome to me! But I didn’t work with it long
enough to take measurements. . . . The exhaust felt and tasted cool and clean . . . . but I didn't take measurements.
I would love to share thoughts, feedback, questions, other design ideas, other problems and possible solutions, as we try to keep everybody warm, safe, and healthy, with those good
permie morals of -- on the cheap and lazy? :D
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