Sometimes I think the rocket mass heater has been the most irritating, stressful, and disappointing project we've ever attempted. At other times, I think it's most exciting, interesting, and cool project. Something about the rocket mass heater concept really captured my imagination. I love the idea of a self built stove that's super efficient and also creates a unique, and warm, piece of furniture. My internal potter gets a kick out of using clay from our backyard to build with. There were times during the planning stages of this project, that I would get so excited that it would keep me awake at night, trying to figure out the best location and layout. I found gathering the material, reading about how the stove works, and all the planning to be really interesting. Making the stove was lots of physical labor, but it was fun because it was all new building techniques for us, like laying brick and stomping cob, and because we had friends who were interested enough in the stove and the process to help us build it.
I think it's safe to say that Brandon wasn't as excited about the rocket mass stove concept as I was, especially in the beginning. He was hesitant to dedicate so much space to it, was worried it would be too heavy, or ugly, or dangerous. But, once we fired it up for the first time, and could feel all that heat radiating from it, he was loving it. High fives to us! This stove is awesome!
But... we started having problems because the draft would reverse. Having a column of smoke billowing into the house is so much more horrible than I would expect. In a matter of moments, the house is filled with smoke and panic. The panicky feeling is heightened by the loud insistence of the smoke alarms, one of which starts yelling at us to evacuate. We would scramble to open the windows and doors to the outside, turn on the vent fans, close off rooms so they didn't get smoked, close the firebox with a brick, and run outside in the cold and dark to light a piece of paper in the exhaust and get the draft to go the right way. Try doing all of that when you can't breath because of the smoke - It's awful! And now we're cold and smell like smoked ham, to boot. Stupid stove.
We thought the problem was with the exhaust pipe. That it was too short, or getting too cold. So we made it taller, wrapped it in insulation, and tried using a heat lamp inside of it to get the draft to work. And it did work - for a while. But occasionally, the draft would reverse. Stupid, stupid stove. We thought there must be problem with the design, a tight spot in the stove - maybe the barrel was too close to the heat riser which would create a pinch point and we should raise the barrel. We really didn't look forward to dismantling the rocket mass heater because it was so much dirty work to put it together. On our way home, late last Friday night, we decided to just bite the bullet and take the barrel off and see what what going on inside. Brandon walked in the door, grabbed the barrel, twisted it, and then ripped it right out of the cob base! I thought it would be so hard to do!
We could see right away that the perlite and clay mixture that was used to insulate the heat riser was so crumbly that there were voids in the metal wire basket, and that the thin clay patty that I put around the top was broken and falling in. Not very aerodynamic.
We could also see that the space between the heat riser and barrel was big on one side and barely an inch wide on the other. On Saturday morning we chipped the clay off the top of the perlite and used the shop vac to suck up all the perlite from inside the wire basket. We made the wire basket a little smaller, placed it so that there was plenty of space all the way around, remixed the perlite with water and clay, put it back in the basket, packed it in there better than before, and formed a thick clay top that wasn't so flat, but more rounded, like the picture in the book.
We used a chisel to smooth some of the cob on the inside of the stove, and to make a place to put some brick fragments to set the barrel on, so it would be three inches from the top brick of the heat riser. We put the barrel back in place, and used a little cob to seal it in. We could tell by placing a the flame from a lighter over the firebox that we had a really strong draft - going the right way! By Saturday afternoon, we had a fire roaring. Of coarse, it was sixty degrees outside on Saturday, so we didn't really need a fire, but still - it was working!
So the stove has worked for three days in a row now, and we've had no horrible smoke panics. Thank you, Stupid Stove! I can tell the draft is stronger than before because the stove roars louder. The barrel doesn't get as hot at the top as it used too. The dragon doesn't get such steamy breath. Last night the cats and I spent some time reading, talking on the phone, and staring into the flames while we snuggled near the barrel.
The cob is starting to get warm in vicinity of the barrel, which the cats and I appreciate. I hope now that the warm air inside the stove isn't constricted, it will flow though the stove better, and warm the cob bench. I'm not sure how long it will take for Brandon and I not to be gun shy about the stove. I still half expect billowing smoke at any moment, even though the draft as been strong. But maybe, just maybe, we fixed it!