Firstly, Thank you all for having and being here in this forum of innovation. It warms my heart to connect with folks that truly think outside the box.
I have been researching for some time and feel I have a good grasp of the concepts and methods, sufficient to take some "next steps" in the basic engineering of these stoves. I can see some of the inherent issues associated with thermal gradients and stresses in the commonly used materials and being a Toolmaker, I have fairly good skills in troubleshooting designs of all sorts.
It appears that the primary area of premature stove failure is in the materials used for the extreme heat areas of the stove, specifically the lower portion of the riser tube. After some consideration and noodling about this issue, I have an idea that I would like to pass on to the group for feedback and possible testing.
It is clear that a refractory material is necessary to line the riser in order for it to last for the maximum time. Common materials used in the research I have seen are fire brick and pearlite/clay mixes, both with inherent issues. The brick option takes up a lot of space and is difficult to insulate and the pearlite/clay mix requires a form to maintain integrity of structure and that form, typically steel tube, will go away after a few seasons.
So, I have thought of a potential solution.
I have found castable refractory materials that, although a bit pricey, will handle the 3000 degrees and survive the heating/cooling expansion/contraction cycles quite well. My method to use these is this.
Roll out a thin slab of this castable material like rolling out a pie crust, with wire mesh embedded in it for stability (I suppose one could use any adjunct commonly in use if one has trouble with wire mesh), wrap this "crust" around a disposable form or even the commonly used stovepipe, then wrap that in rockwool with a split stovepipe covering to hold it all together. This should provide a riser life that far exceeds the common steel riser, far greater insulation and performance than firebrick and with careful packaging, should be able to be shipped or moved easily without damage.
The choice of castable refractory material will need to have some variability in its mixing to create a fairly thick consistency, like pie dough, but I don't see this as a significant issue.
If one were to roll out the "dough" on a fireproof cloth type material, the rolling around the form will be rather easy... If in doubt, ask Gramma how she keeps the pie dough from sticking to the breadboard... She will have some great ideas that can be adapted.
Curing of the "dough" may require it be open to the air for a time, but I don't see this as a significant issue provided the stability adjunct (wire mesh, hair, straw, whatever) and the cloth you roll on can support the weight without distorting or allowing the "dough" to flow or move.
I would like to test this myself but personal issues prevent me from experimentation at this time.
So I put this to the community for perusal, disassembly and debate in the hopes that one of you intrepid pioneers have or can obtain the materials necessary to further the research.
Thank you for your time.
Jocelyn Campbell wrote:The innovators have discussed creating a rocket stove set up that could either scald harvested pigs or be used as a hot tub
Leila Rich wrote:I was about to link something about a NZ tradition; the fire bath.
Heaps of fun, but requires balancing on a wide board or you burn your bum-'bathing as extreme sport' kind of thing
When I searched 'fire bath', what should be at the top but rocket stove fire bath
allen lumley wrote:Colon S. If past experience AND the 2nd edition of Ianto Evans 2nd eddition of Rocket mass heaters is to be believed, with the minimum spacing of 1.5''
between the top of the Heat Riser and The Inside top of the barrel for a 6''RMH system, And 2.0'' for the minimum spacing of the gap between the top of
the Heat Riser and the inside top of the Barrel -If the barrel is off set the narrowed side is always cooler and the wide side is always hotter !
I have some experience with 3 RMHs built to that pattern, and they do often appear to follow this rule! this is common to all 3 RMHs constructed with
minimum gaps between the H.R.s and the barrel !
I have zero experience with a larger H.R. to Barrel gap, but there is still a frequent referral to anecdotal evidence of a reversal in the heat patterns when a
Larger H.R. to Barrel gap AND an off-set barrel to H.R. placement are both used, your explanation of the greater area given to gas flow through the
transitional area is a fair description of what we are seeing, it does NOT address the basic issue, whether or not off-setting of the barrel continues to affect
the hot gases flow, and how it does so ! for the Good of the Crafts! Big AL.
Julia Winter wrote:I'd like to hear what the batch heater is for, or what it does differently. I can see that the circular bench is a way for a group of folks to sit around in a comfy circle outside at night, but I can't discern the idea that led to the batch heater.
Burra Maluca wrote:I've embedded that video for you.
paul wheaton wrote:I think we need to start putting together a list of materials for next year.
We had a small mountain of barrels and I'm pretty sure we could have used a few more this year.
How many barrels did we start with this year? Whatever it is, we should probably triple that for next year. And maybe build up an inventory of lots of different sizes.
It seems we went through a lot of fire brick. And the red brick with holes. I think we need lots and lots of all sorts of clay brick (not the cement stuff).
Tom Rutledge wrote:
I am a data nerd.
Tom Rutledge wrote:
water fittings / tanks... sized like a hog scolder or an artificial hot springs. cuz' if stuff is just laying around and out, someone may put it together.