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Cast Masonry Rocket Mass Heater....some thoughts

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I am new here.
I have never built an RMH before. I have read most of the books, watched videos, and am contemplating starting my first heater.

My thoughts: to build a full masonry heater for a garage (initially) that does not use a lot (or any) firebrick and no big metal drum for the outer surface.
I just can't get over the looks of the metal drum. I think it looks like crap. Sorry if that offends anyone, just my opinion. I also question their longevity given the high heats etc (but, hey, they can be replaced, right? no big deal).

Anyway, I am going to build a set of molds and use a castable refractory to build the entire structure. Many of the large components could be poured up, some will have to be poured on the side like bricks, and bonded on.
I'm pretty sure I can get the whole structure up to the upper most lid by pouring in place. The lid would actually be a separate piece, possible interchangeable to be a masonry top, or steel lid for cooking on.
I plan to try using a recipe from Dave Gingery's books on home foundries for casting aluminum. Basically it's a 2:1 mix of fireclay and silica sand with enough water to make it thick. It holds up well for those foundries with very hot, blown-charcoal fires so I'd think it would work.

Any thoughts? I'll come back when I get started but wondered if anyone else has gone a similar route.

Bill in GA
Posts: 112
Location: Groton, CT
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With no barrel to release heat, where will the Delta-T come from to DRIVE the RMH?

You can certainly use ONLY the thermal mass to create the Delta-T, but it will not be self-starting. You will need some sort of forced exhaustion to get the exhaust gasses moving. You can also use other metal devices more aesthetically pleasing than a barrel as well... But the fact remains for a self-exhausting RMH you need to create a large Delta-T as close to the burn chamber as possible.

I have toyed with the idea of using a water jacket instead of a barrel, but it will need a water pump and heat exchanger to work properly.
Bill Rayfield
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Guess I was thinking of it having a slower initial burn more like a Masonry stove but with a RMH style layout.

Posts: 2482
Location: FL
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There are castable refractory materials out there with a proven track record. They take the heat, punishing flames, cooling and heating cycles and hold up beautifully.
KS-4 I've worked with extensively. Can be mixed up in a wheelbarrel, poured into any form you can imagine, 2800 degree rating will meet your needs.
Harbison Walker has this listing of refractory contractors. You may be able to find one near you and get what you need.

this is supposed to be a surprise, but it smells like a tiny ad:
Rocket Mass Heater Plans - now free for a while
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