buildt my own rocket mass heater

...wanna see?

http://twobirdstone.blogspot.com/

I was going to build one for e Farm in MO but they decided they needed pyrolysis oil over this simple but beautiful rocket stove technology...

Built one anyway in NM, heats the shower floor and perhaps the water.

So your combustion chamber is brick?

Did you use cement for mortar?

The stones will be part of the floor, right?  So ....  I wonder if that might get too hot to walk on barefoot?  (but this is me just wondering - I'm happy to be told why my thinking is foolish)

...the entire J tube is fire brick (64 of them).

I used Veriset which is a plastic glue meant to set and high temperatures and withstand temperatures (so I was told) of 3,000 degrees F. So far it has held.  So you're right, my building materials aren't renewable.

-later, I will build a smaller rocket stove soley with abode and rock: I had to get this one done quickly ...didn't have vehicle time to scavenge in nearby cities for used brick.... nor did I have the time to test local rock for trapped moisture (can't have rock exploding on a finished product).

Realizing the floor might get too hot to stand on, I laid the horizontal pipe over volcanic scoria (red in the pictures), known here locally as cinder. The scoria is full of air and about 6" to 8" deep.

The scoria is not entirely covered nor sealed and leaks heat around the edges (maybe 1" around the perimeter of the mounded floor).

The longest I've fired the stove to date is 2 hours at which time the 3 inch thick rocks just barely begin to get mildly warm to the touch. The 3" rock which makes up most of the floor, seems to be a volcanic powder mixed with clay and pressed over the eons into rock -so it takes a long time to get hot.

So I may have errored by letting it leak TOO MUCH heat out through the scoria.

The water does get hot, though that circuit isn't show in the pics... I'm headed out there tomorrow and may post again if I get to Internet access.

I will be out in the area until spring so you may not see another post from me until then -so please realize I'm not being rude, just not where I can get Internet access.

BTW Paul, I had posted before as negilgiblek, forgot my password, but your password retreival system claimed there was no such user as negilgiblek ....I'm probably overlooking or forgetting something.  Not to worry, I'll just keep posting as twobirdstone.

twobirdstone wrote:
...the entire J tube is fire brick (64 of them).

I used Veriset which is a plastic glue meant to set and high temperatures and withstand temperatures (so I was told) of 3,000 degrees F. So far it has held.  So you're right, my building materials aren't renewable.

-later, I will build a smaller rocket stove soley with abode and rock: I had to get this one done quickly ...didn't have vehicle time to scavenge in nearby cities for used brick.... nor did I have the time to test local rock for trapped moisture (can't have rock exploding on a finished product).

Realizing the floor might get too hot to stand on, I laid the horizontal pipe over volcanic scoria (red in the pictures), known here locally as cinder. The scoria is full of air and about 6" to 8" deep.

The scoria is not entirely covered nor sealed and leaks heat around the edges (maybe 1" around the perimeter of the mounded floor).

The longest I've fired the stove to date is 2 hours at which time the 3 inch thick rocks just barely begin to get mildly warm to the touch. The 3" rock which makes up most of the floor, seems to be a volcanic powder mixed with clay and pressed over the eons into rock -so it takes a long time to get hot.

So I may have errored by letting it leak TOO MUCH heat out through the scoria.

The water does get hot, though that circuit isn't show in the pics... I'm headed out there tomorrow and may post again if I get to Internet access.

Hey, twobirdstone,

Nice looking stove!
It takes a long time for any stone to heat through; if what you have is natural insulation (lots of pumice pockets), then you may have just created a really high-tech insulated floor.

We use a rule of thumb of "an inch an hour" for heat saturation of masonry.  If you've got 3 inches of stone on top of that thing, and it behaved like most masonry,  I'd expect it to keep warm (and maybe even get hotter) for another hour to three hours after the fire goes out.  Does it?

What happens if you heat it a couple of times on the same day, or a couple of days in a row?

What happens when it's dry vs. wet?

The airflow through the scoria (and evaporation from your shower water) will cost you some heat.  Over time, ash buildup in the pipes may tend to insulate their undersides, concentrating the heat in hot areas where it does some good.  I like the scoria for drainage.  You might be able to seal the edges of your floor somewhat, reducing airflow through the scoria.

Not sure why you'd want to heat a shower floor, but I can't argue with the way you did it. 
Cob or adobe wouldn't hold up under running water, so modern masonry materials may be the way to go in this case.  Hydraulic lime might be an option if you're careful about channelling water away using stone or tile.

Any temperature results?  I'd love to see them on my "Got Rocket Mass Heater?" topic for our code approval efforts here in Portland.

Thanks,
Erica Wisner

http://www.ErnieAndErica.info