I haven't even built an RMH yet. I want to for a greenhouse but I was wondering the same thing. Whether or not pellets could be used. If they could then how could one create a gravity feed hopper to continuously fuel the flame. If you actually look at a pellet stove in operation it is actually quite similar in function to a rocket stove with the fuel being burned more completely. This would have to be an outdoor in the summer experimentation thing.
It seems like it ought to work. The trick would be making sure the burning didn't travel back up the feed tube. I'd say to think about some kind of weight or spring driven clockwork mechanism to dump a small load of pellets into the combustion chamber at regular intervals, so there isn't a continuous line of fuel leading flame slowly back up into the hopper.
I have a question about RMH. People use cobb because the clay is readily avaible and it won't crack going through the heat/cool cycle over and over, right? I have zero access to clay. Using concrete or mortar would be a bad thing, right? How about a block wall with the cavities filled with sand and the piping for the RMH in a sand filled cavity?
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