Compact Rocket Mass Heater

We built a compact RMH last year from scrounged chimney parts and firebricks. It keeps the kitchen in our place warm if we fire it up for a few hours. We turn on fans when it gets to be about 275 degrees on top. We burned mostly pallet wood last year and this year will be using scrounged wood from well seasoned forest slash piles that were never cleaned up.

johanna Sol : Thanks for sharing ! Can you share your location and the size of the space you are trying to heat ?
The following links should help with using Permies.com

https://permies.com/t/43625/introductions/Universal
https://permies.com/t/34193/tnk/permies-works-links-threads

Thanks for sharing ! for the Good of the Craft ! Big AL

Went ahead and embedded your video, hope you don't mind. Nice little build you've got there, thanks for the video.

Nice little thing. Shame you didn't add a bit more surface of bells. So you could extract more heat. What have you done in the second bell, with that metal bit on top? You have a plunger tube in there? May be, if you could find more clay flue, you could add one on top with not much effort. As well, if you dismantle your stove one of thoses days to rebuild, make the oppening from frist "bell" to the second; wider, this way you will have less restriction, and it doesn't change neither the strenght, nor the heat exctraction capabilities of the bells. Just lets the rocket breathe a bit more.

My reading of the second bell's metal fitting is a reducer going from the top of the bell to the chimney. This makes it not actually a bell, just a wide chimney section, and it will not hold hot gases to let them cool and radiate; rather, the hottest gases in there will go up the chimney. I realize your space is constrained, but if you can't exit from the lower side of the bell, you at least should make the exhaust pipe draw from near the bottom instead of the top, by running it straight down inside the bell. (This is the "plunger tube".)

@ Michael - Appreciate your kind comments. Definitely don't mind you sharing the video as there appears to be a dearth of mini RMHs and this may help others.

@ Allen - We are in High Desert country at close to 5000 feet so winters can get below zero. Kitchen area is about 20 x 12 so 240 sq ft; hallway nearby is about 30 sq ft; two rooms off that get a little boost in temp - about 140 and 120 sq ft, respectively... these have solar hot air boxes that work great on sunny days. Cloudy days in mid winter we ran the stove for many hours. Backup system is forced air "natural" gas.

@ Glenn & Satamax - Thanks for your input and suggestions. We didn't go for max efficiency since this was our first attempt at an RMH and we wanted to use what we were able to get cheap or free as well as get an idea of how well it worked. Had ideas of building a bigger and/or system but doesn't look like it's happening this year due to time constraints.

Hi Johana.

Well, if you want an increase in efficiency, you could try to convert it to a batch rocket. http://donkey32.proboards.com/thread/1361/converting-8-6-batch


And i reiterate my question, does that metallic tube go to nearly the bottom of the bell? If not, do it ! You will increase your heat extraction big time.