Surplus Clay! - ideas for planning please?

Hello everyone,

I did a search using the title clay rocket stove and got one hit that wasn't what I was after so I'll do a shout out and see what comes back. I've built many rocket stoves of smaller nature from gallon size paint cans (metal). I even incorporated heat exchangers into the stoves that stood on top.

I'm now living in Mexico where there is only about 2 months of the year that get cold enough to want a little heat which is usually in November through early January. I'm wanting to build an outdoor kitchen to include a cooking rocket stove.......maybe from clay. I also want to build a rocket heating stove without the heat storage as I don't think it would be worth the effort as I'm thinking only of having something to take the chill of the evening air off inside the house. Houses here have no insulation.....just brick mortar and plaster so it can get cool in the evenings while watching a movie etc.

I recently discovered the local arroyo possesses oodles of decent clay. I dug up half a five gallon pail of it and slaked it down after drying it and then dried it again leaving a very clean clay that passes the worm around the finger test without cracking. The clay seems to have good plasticity.

The cooking stove;

I'd like to build either an L style or J style with the clay by finding a good recipe for a mix of clay and maybe sawdust and sand to make if from without it crumbling and falling apart after a couple uses. The J style I think I'd have to build a framework to support the heavy pot on top as I'm not sure if a clay mix (roughly 7 coarses of brick high) would be strong enough. Can/should I think of also using things like cement for strength to support heavy pots, and perlite vermiculite etc. for providing insulation for the firebox?

The heating stove;

Rather than using fire brick for the base (my floors are all cement with ceramic tile on top) could I utilize the clay I have found to make a thick slip and add perlite for a thick mud and pour a rectangular base and let dry, then build the firebox/combustion chamber/riser tube etc. on the clay perlite base? I suspect it would insulate the combustion chamber well from the floor keeping the heat in the fire where it belongs. Maybe building everything in contact with the floor would be better to transfer a little of that heat into the floor for a slow thermal release?

There is a tile here that is made from clay for roofing and flooring tiles called baldosa which is a red color. I've seen the folks at Aprovecho making use of this tile in areas where other materials can not easily be sourced. I just don't know how it would hold up to the heat of a rocket stove heater or cookstove.

In short I'd like to utilize locally available free materials and enjoy the process if I can. As I have a good source for clay, could I utilize it in other ways in the building of the heater by surrounding the firebox assembly with clay slip and perlite to seal the whole unit leaving the feed box open of course? I'm open to all ideas at this time as I'm still in the gathering materials phase. Thanks

Oh, one last thing. Rocket heaters work best when there is a large difference in temperature from the inside and outside air. With temps here rarely falling below 10 degrees celsius, will a heater run properly?

There are those here that know better than I, but I'll give my two cents.

Don't use cement as it will crumble apart at relatively low temps. I would think making your own clay/sand bricks would be plenty strong for heavy pots.

Check out this link https://permaculturenews.org/forums/index.php?threads/adobe-rocket-stove-with-bell-heat-distribution.12342/ for an awesome cob brick solution to the metal bell. The perlite cob base should work well for insulation, maybe even a layer of empty glass bottles like we do with cob pizza ovens? Anyone doing that for insulation?

Daniel Ray wrote:

Don't use cement as it will crumble apart at relatively low temps. I would think making your own clay/sand bricks would be plenty strong for heavy pots.

Thanks Ray, I saw on youtube a couple rocket cooking stoves made from concrete. I wondered if cement and perlite would otherwise hold together better and break down less....nice to have alternatives. I had not thought about making my own clay/sand bricks. I was going to just do it cob style and use 4 inch pvc pipe as the form for the elbow. I need to find some recipes for a refractory clay/sand mix.

Check out this link https://permaculturenews.org/forums/index.php?threads/adobe-rocket-stove-with-bell-heat-distribution.12342/ for an awesome cob brick solution to the metal bell. The perlite cob base should work well for insulation, maybe even a layer of empty glass bottles like we do with cob pizza ovens? Anyone doing that for insulation?

I very much liked this build. By taking the exhaust out the side rather than inline it could save a lot of space without sacrificing performance.

An all-clay rocket stove is totally feasible. This thread has photos of one I built a few years ago: Clay Rocket core/Bell/RMH system?

Glenn Herbert wrote:An all-clay rocket stove is totally feasible. This thread has photos of one I built a few years ago: Clay Rocket core/Bell/RMH system?

Nice, I like it. Did you find feeding wood into the feed tube awkward at that angle once the cob was all on? I think the L style are more efficient for cooking but I prefer the J style for ease of use.

How many firings did it take before your sacrificial core was gone? Scrap plywood? tnx

Not awkward at all. Using relatively short wood (12" I think) in keeping with the scale of the system, I could lean the sticks forward against the stove wall and get good burning, with the fire going through the load instead of bypassing it and going straight into the burn tunnel. What I have heard is that the J-tube is more efficient than the L. I have built both and they both work.

The scrap plywood and board core burned out in the first firing, except for the bottom back corners of the feed tube which took a few firings. I eventually pried the last bits of form loose and put them in the main flame path. The first firing was with the cob still wet; in fact, I needed to fire it so the outsides would firm up enough to continue building. I built in a lot of voids both for insulation pockets and to minimize the amount of cob. There was no good source of clay nearby, so I imported a few buckets of clay from my house.