I have just finished building my first Rocket Mass Heater (RMH). And I am amazed! WOW. The center burn chamber sounds like a rocket engine on just a couple newspaper pages.
I’ve been following the RMH discussions on permies for a few years and saw a couple RMHs first hand while living at Lost Valley ecovillage and visiting Aprovecho, (global leader in rocket stove technology) and I’ve built a couple small ones for demos outside.
What is an RMH? It’s a modern version of a European masonry heater (albeit a LOT smaller).
The one I built is a ‘J tube’ configuration which means you load the small wood stocks upright and the horizontal flame shoots through the burn tunnel and up the …..
Many thanks to Ernie & Erica and also to Paul Wheaton (world dominator wanna be 🙂 . I used their plans from a Portland building code project. And it worked the first time.
There are four main components to an RMH: Feed chamber, burn chamber (cylinder), recirculating ‘barrel, and the exhaust piping. that’s it!
Here are the construction steps I took (using existing stuff):
- find/count all existing bricks: 80 clay, 35 cement, 30 fire brick.
- Found 10″ OD burn chamber with 6″ ID – 48″ long, and 30 gallon steel barrel.
- Measure floor area, design, calculate… revise, revise again.
- Draw out rough plan on floor in-place, lay (dry) first course.
- Think about it, ponder, redesign, refine, redo.
- Stack 2nd, 3rd, 4th (dry) courses. Conserve firebricks.
- Put inner chamber and outer barrel on, test fire: WOW it drafted!
- Mortar up 1st and second courses. Mix perlite/clay/sand.
- Fill burn chamber with mix.
- Finalize entire brick base, put barrel in place and test fire.
- Install exhaust piping, hole in outer wall, test fire again.
- Final sealing to eliminate all indoor smoke.
I’ll post some pictures soon….
Two most important things are getting a quick fire drafting through, and avoid any indoor smoke. i learned that the hard way… and now put one little newspaper way inside the feed chamber…making sure the burning newspaper doesn’t get sucked into the central burner cylinder.
Don’t try to brick&mortar exhaust port to barrel – just cut a hole in the barrel for the exhaust pipe and seal with Fire retardant caulking.
I used thick glass putty (fired & cured) to seal lower barrel lip tightly to prevent smoking.