rocket mass heater brick kiln

ok, so ive read a lot about rocket mass heaters for the past week. and plan on building one(not a cheapo one) this summer for use in the following winter. Im also looking into making a cob/straw bale constructed living space for the outdoors that it would go in. well in doing all this i will refine my resource gathering and processing skills and will more then likely find ample supply's with time and dont want any of them going to waste. so i had the idea that i could mix up a clay/sand brick mixture and be able to slowly dry and fire them through the rocket mass heater. i DONT want to make fire bricks, i want to make bricks that are weather/water proof such as a stepping stone, flower bed edger, or just a general brick. My initial idea is to make chambers in a couple places throughout the exhaust, one near the barrel, one or two in the middle, and one at the end. these will be pre-firing/drying stages and bricks will slowly be moved up from the exhaust to closer to the barrel over a period of firings/days. the final firing will done on top/inside the heat riser barrel. The whole system will work like a very slow assembly line maybe producing 2-8 bricks a day when i use it, and the humid heat in the exhaust system will help dry the inside of the bricks before firing. so now for my questions.

1. i need to access these chambers in the exhaust either from above or from the side and i need a door or access point that will leak the least. will a small leak destroy the system in this stage?

2. the main firing chamber is a bit of a harder question. i thought about making a small oven that would sit on top of the the main barrel and just trap the heat with the bricks, but im not sure i would get high enough temperatures even with an insulated over on top and with an artificial draft to overcome any stalling. ( any thoughts?). my other idea was to arrange bricks around the top lip of the heat riser inside the barrel, but this would require a high temp leak free access point. and i feel a leak would be bad at this stage, is that true?

3. what temperatures are found inside the top of the barrel? not the top surface.. i know how hot it gets and i sure it would need insulation to get the temps i need.

temps needed to make average bricks is below 2000f. most sources say below somewhere 1800f for a long period.

PLEASE DONT get side tracked and tell me its not traditional... i will used forced air if needed to make bricks but i want it to run fine when im not doing bricks to so im still trying to keep with traditions. but i love technology and advancing technology. and whether you accept it or not this is technology and it should be integrated with newer technology if it makes it better and more accepted. for the good of the craft. but mostly i need ways to make leak free access points if its possible... i think this would be a great way to make bricks in my spare time a hand full at a time and also heat the space i want to.

Drying chambers inside the exhaust ducting sound like a lot of work and possible issues, not to mention that the exhaust gases will be quite moist and may not easily pick up more moisture.

I think you will get better results drying your bricks much easier by just setting them on top of the bench, perhaps lined up along the back edge out of the way protected by a back-board or something, shifting them along the bench toward the barrel as conditions warrant. Stacking them in a lattice pattern around the barrel would be the final step before "firing".

I am, however, quite skeptical that there will be enough concentrated heat above the riser to actually fire bricks evenly; at best, one side would get fired while the other side would not, which might cause cracking. If you are not wanting a concentrated hot spot with the barrel top at a convenient height for cooking, you could raise the barrel several additional inches above the riser to allow stacking say 4 or 8 bricks on top around the edges. This would require a very durable riser, probably built of firebrick splits instead of cast. This would at least not interfere with the basic heating function of the RMH.

If you want to do this, you would need a barrel with removable lid and clamping ring (something many barrels have) to make access relatively easy. This would probably necessitate more frequent replacement of the gasket which seals this joint.

I think you would get better results by making and stockpiling your bricks in a warm dry location, then building a brick kiln when you have accumulated enough to be worthwhile. A tight wall stack around the edge will allow the center bricks to fire evenly. In the next firing you could move the outer bricks to the center. Or if you really want a lot of bricks for building, you could build a real brick kiln with insulated walls.

Any bricks you make without a good dedicated kiln will be soft and uneven enough that they will not be durable for outdoor use in a freezing climate.

bryant berry : You did not share a location, this helps a fellow member who may be a near neighbor with Cob experience to help point you in the right direction !

I am pointing you at a source for a little traditional information be cause there is only an approximation of traditional and 're-inventing the wheel '!

After you have a working formula for the local clay and sand, by all reports you can dig a trench and experiment with firing a terra cotta type brick, the most
common way after that was to start off with a hugh pile of bricks to start with because brick kilns were made with - - - - Bricks!

So I have dug out from a BBC series on the (WW11) WAR FARM where they show the tremendous amount of work that goes into brick production on the small
scale, Good luck tracking down more information, and please do share the adventure ! For the Good of the Crafts ! Big AL

Link below !

http://youtu.be/bxztuX3fGVM?t=6m42s

Hello Bryant,

In the beginning of this post topic, it seems an outline of asking a question and presenting a subtle query..."will this work and is it feasible?"

My reply would be, as a ceramicist, oven, kiln, and masonry heater builder, I can only suggest that it is neither feasible nor likely to work efficiently. I believe you can "force" just about any concept to be "made to work."

Then the post closes with:

PLEASE DONT get side tracked and tell me its not traditional... i will used forced air if needed to make bricks but i want it to run fine when im not doing bricks to so im still trying to keep with traditions. but i love technology and advancing technology. and whether you accept it or not this is technology and it should be integrated with newer technology if it makes it better and more accepted. for the good of the craft. but mostly i need ways to make leak free access points if its possible... i think this would be a great way to make bricks in my spare time a hand full at a time and also heat the space i want to.

To this all I can say is, do as you may, and please share the outcomes of the experiment.

Should there be a desire to present a true "open query" once more to those of use that have seen many examples around the plausibility of making brick, tile and other ceramics in all manner of wood and gassed fire chamber...the answer is:

"This is neither efficient nor practical...

RMH are a type of...masonry heater...and...kilns are for mass firing with very serious temperature control requirements, with huge fuel consumption and then must have very controlled cool down periods. Mixing the two modalities can be forced together, of this there is do doubt, yet when this is done, you will be loosing effectiveness in both and practicality in neither.

Good luck with your experiments,

j

no one answered my question about door/access point making. except for the barrel top seal advice. i know it will not be efficient. its not made to be, i just wanted to have something extra to do on the farm. and i figured making one or two bricks a day i wouldn't hurt myself. so i wouldnt even call it small scale brick making. its just using what i have to make something else happen. i dont want to make a whole kilm, i will never have that many bricks to do at once. i like the idea about stacking them on top of the cob bench to dry but i had already planed to do that as well as other outside drying stages in the barn. i do feel that the temps are possible above the heat riser, i will just need a thermal mass, insulation, and forced air to keep it from stalling. and i figured because the whole oven has a lot of thermal mas that that the temperatures it creates would be fairly constant and would slowly lower back down to room temp like in a kiln. does anyone know how much humidity is in the exhaust? alot of people wet the bricks during the drying process to keep the outside wet and the inside slowly drying. but the humidity at different temps throughout the exhaust would make a difference and difficult.

I want help with access points... dont tell me its not possible... nothing is done/bought yet.. so if you cant help, dont. we put people on the moon for no reason.

how hot is the exhaust at certain points? and has anybody ever took humidity readings in the exhaust? what kind of access point do you use for your ask pits? and no one answered my questions about leaks and their effect on the system.

Bryant, you are probably going to reject this observation.

The downside risk on your concept is carbon monoxide poisoning.

Rather than take that chance, to try and make some bricks "just using what you have to make something else happen", does not seem to me to be a very reasonable idea.

Perhaps rather than insisting on pursuing this project, you might consider something else that you could do that would not have quite so large a downside.

this is why im asking about leaks and seals... i wont do it if its hazardous to my health.. thats why im asking about access points... if they cant be made then the project is dead.. i cant make a space age seal.. but i can make alot.. im sure someone out there has an idea. and i really just want to make it have more then one purpose... i can heat water, and cook food. but i feel there is always more you can do.. and i wana use the heat. and any bricks in the system would add heat mass.

While I agree with Jay that it can never work well, and would be a lot of effort for a mediocre result, the access ports you ask about would be the same thing as cleanout caps, which are a common and necessary feature of any ducted mass system. You could insert a few bricks into any cleanout port that was big enough to use easily for cleanout purposes; you would just have to ensure that airflow was not restricted by your bricks.

how air tight are these caps? airtight? thats kinda what i thought was out there, some kind of cap. well i also might not try and have multiple chambers. maybe just one before firing, and that wont add much to the original design other the the topper i would have to make to try and create an oven on top of the barrel. but i want this topper to come off as well so that it works as a normal rmh with out a fan. i dont mind using a fan to put more heat into the top of the barrel when i need it. why wouldn't the insulated oven work well? and would only having one pre drying chamber at the ash clean out be more feasible? and just dry longer prior? it doesnt have to be a big chamber in the exhaust, just enough to move air around the bricks. i just thought more would be cool. do these clean out cap you speak of come in different sizes?

Hello Bryant,

I am going to try again, to perhaps suggest a way of thinking of this and also a better format for "getting" and "receiving" assistance on this topic and others on this forum. I try (really hard) most of the time not to go into "teacher mode," yet when a question is asked from the "less experienced" to the "more experienced," I become dismayed how some folks will then want to either "debate" the answer, and/or dismiss it.

"...I want help with access points... don't tell me its not possible... nothing is done/bought yet.. so if you cant help, dont. we put people on the moon for no reason..."

Asking a question then saying don't give me an answer is rather "bossy" and also counter productive. I have already suggested that you should experiment with whatever you are thinking. The door design and related details will have to be up to your imagination as the entire concept is fraught with potentials for either accidents (i.e. carbon monoxide poisoning, explosions, etc) to simply not achievable with the suggested design.

Yes we went to the moon...but we did it in a "space craft" not a "sail boat."

So, again, a kiln is a kiln and a RMH is a masonry type heater...the two are vastly different combustion units.

"...no one answered my question about door/access point making. except for the barrel top seal advice. i know it will not be efficient. its not made to be, i just wanted to have something extra to do on the farm. and i figured making one or two bricks a day i wouldn't hurt myself..."

I tried to answer..sorry...let me be more direct...This won't get hot enough, for long enough to even reach a reasonable "bisque firing," let alone make a single brick.

"... i do feel that the temps are possible above the heat riser..."

Yes the temperature could well reach those required to fashion a few bricks...absolutely...but only if you can maintain them for over 24 hours and then maybe twice that in a controlled "cool down." Then you would have your one or two bricks.

If any other potters, or related see "holes" in my logic, please correct me...I would be fine with having missed something that could render this plan achievable ...and...safe.

Regards,

j

and i think personally this can be more efficient/cheaper then me making a kiln i dont use enough and me having a rmh that just makes heat for a room... i could wear a jacket if i really cared about efficiency of my rmh.. I DONT CARE ABOUT MAKING THE BRICKS EFFICIENTLY. they would just be a by product of heating the room and burning wood. im not trying to open a brick shop... but i like messing with clay but not enough to set up and run a kiln...

O.K....got it...just messing around...

Are you seeing that you are not going to reach the required temps for long enough to make a brick, or able to achieve the very "controlled cool down" required. I have tried explaining that in each post...

well im sorry for sounding contradictory but ive been on this forum a long time and i can read how people will get completely side tracked and completely take over the thread and not help very much... yes i know its going to be difficult.. and yes its new... and as you can see most people are saying its just not possible even tho they only have one perspective of what is achievable and why its wrong and dont help... i just wanted help on certain problems and help with the idea... i can decide on my own if its worth it... we crossed an ocean that we knew no end to in a sail boat... it took time to build the right boat.. but we made it and it came to America. it just took time... thats all i meant by the moon metaphor. but we thought it was impossible...

ive looked into making bricks... i know what temps are required.. im not trying to make a constitution brick that requires long firings. some bricks use shorter firing times. it depends on what you want. and a mass heater can create high enough temps... i just have to insulate to hold them

take over the thread and not help very much... yes i know its going to be difficult.. and yes its new... and as you can see most people are saying its just not possible even tho they only have one perspective of what is achievable and why its wrong and don't help...

Hi Bryant,

Hmmm...o.k....It is neither "new" or within the realm of simple pottery/ceramic physics. I am not sure if you could even safely make a very soft brick as there won't be a "bisquing" achieve for long enough. I am not trying to take over your post by any means, and if you tell me..."thanks but no thanks to advised shared, jay..." I won't keep posting at all here and leave you to your experiment.

I didn't really won't to play the "chicken little card" about skies falling, yet have to share that I have known personally of two deaths in kiln explosions, which happens at these temperatures when clay is involved and folks with little experience start pushing boundaries they may not quite understand completely. Your metaphors are great, yet missing the points I and others have tried to share. Water is wet...law of physical characteristic...no matter what it is going to remain wet...even if frozen, in vapor, or some other state...not a great metaphor......but the point is...


The suggested combustion chamber will not be...hot long enough... or....cool down steadily enough.... to make even a good "bisque firing" let alone a functional brick or tile...and...it has the potential of really hurting somebody...

I think I will stop now anyway, and wish you a safe journey...

well what are the temps needed for a bisque fire? and to avoid leaks with the barrel i will probably just make something that sits on top of it and insulate. i know i might have to deal with the barrel getting to hot and disintegrating and replacing it or using different metal. isnt the heat coming directly from the heat riser still super heated? i would just have to trap it correct? the only reason i even thought of this idea was because rmh could easily reach 2000+ in the burn chamber and riser and i only need atleast 1500-1800 for a normal decorative brick. the time varies alot.. some go for just a couple hours to a couple day.. and the rmh would hold enough heat to slowly let them cool. also letting the bricks dry a lot helps with cracking to, which was the reason for the drying chamber. im not trying to make factory made quality bricks.. or fire bricks... and all i need is thermal mass and insulation to control the temps and hold them in the oven, so i dont see how my bricks would cool off to quick. i also thought the rmh would be a good way to control temps since im not directly over a fire and i can have it insulated and safe inside the oven topper and vent excess heat in oven if its created.

i think this would also be a good way to make dining plates as well maybe. and all that was truly meant by my metaphors was that i want to build something that has not been put together in such a way that it performs the task i want and deliver me to place that im happy. a place where i can fire clay if i felt like it.. and not make a business out of it to make it worth while.. and before telling me its not doable because of today's practices and methods doesnt mean im still not going to try... so you should help if you can.. or ill be lost at sea/space.. but thankfully i wont die if this fails... i just want help at what might be a fruitless task in areas i need help... either way its my failure or success.. so dont take it personally.. i just wanted blunt help.. not round about ways of saying you cant help.. because i dont see anywhere where someone has tried this and failed... maybe its supposed to be me.. i really like the comments so far.. this is a very active forum..

Okay, for the closest I can get to "tried this and failed", I can offer my experiments in kiln-building in the early days of my reproduction pottery career. Building small-scale replicas of English medieval kilns before I got the proportions right, there were instances where I fed an intense fire for four to six hours, getting the inside of the kiln and its contents glowing orange for hours, only to have the results (made from various pottery clays) barely hard enough to not melt in water. You could possibly make bricks, but they would not be much harder than dried clay. It also requires extremely close control on the rate of heating up in the early stages - this is where clay can actually explode, and something with the mass of a brick could cause the kiln/container to be damaged or broken in certain situations. I do not believe a RMH has the fine control to heat at a long, slow rate, and you would not have the sensors to tell what it was doing inside the "brick chamber".

As for dinner plates, that is flat out impossible without a real kiln or a kiln-like structure (not a rocket heater); that shape is delicate and one of the most sensitive to temperature fluctuations, and a plate that is too fragile to pick up by the rim is pretty much worthless except to look at.

A rocket mass heater that is big enough in heat-producing capacity to fire more than trinkets is going to be way too big for heating your house. It's not like you can just add more heat bit by bit until you get a chamber hot enough. The extreme temperatures will radiate/conduct out faster than you can build them up... it's a matter of surface area to volume. A small chamber that would fit on top of a barrel will be much harder to keep hot than a large kiln. You can build a rocket-fired kiln (I've seen a slideshow of a project in South or Central America), but it will not be a good household heater. Go ahead and experiment, but be very careful that you build safely such that a brick explosion cannot cause damage outside its container.

Some further thoughts. Consider a bell system for your rmh rather than duct work. It will give you chambers better suited for adding some bricks. The bells are often made of half a 55 gallon drum. You could weld an oversized clean out chute on the side of the bell to give you access.

Have you thought about how hot the space the rmh is in will get while you are trying to fire bricks?

Historically wood firing has been an out of doors process for many reasons, not the least of which is high temperatures sustained for very long periods of time. It would not be comfortable to hang out in a room with a wood fired kiln working, even if there were no problems with exhaust gasses in the space.
Some times the reason a thing has not been done is not that it has not been thought of, but that it has been thought through and the decision made not to put the further effort into something that won't work.
I think a rocket stove powered kiln is workable, but it does not look like the hybrid idea you are pursuing.

i thought a plate might be to hard to achieve. trinkets would be interesting to make. like i said i just want this for hobby purposes. i want the kiln to be very small/micro anyways. and if it doesnt work out i will still have a working rmh. i understand its kind of a weird extra thing to want that not many people would find interest or even go through the hassle. but i just wana be artistic and multipurpose things. and i might have it heating a green house so i dont think over heating the space in the winter will hurt. i dont plan to do this during the summer. the building i want to make will be hooked on to the green house in order to heat and hang out with my plants. the cob building will be made to keep the rmh away from anything combustible or melt-able. i do understand heat and heat control is my issue.. im not saying its not. and that probably will be the final issue i have to keep dealing with that makes me quit. but i just like the thought of making things with things i made lol. are the ash clean out caps pretty airtight? no one really chimed in on that yet.

you guys have given lots to think about. i understand how alot of kilms work. but you also have to remember that people dont make kilns for a brick or two, and if they do they are not efficient either . any kiln that can actually call its self a kiln will be made for the sole purpose of making multiple things in a timely efficient manner. what i want to achieve is small compared to any kiln. and i dont want to fire outside with a pile of wood because that would waste my wood and that seems like it would take an expert or tribe to pull off right. and i dont have the money to make a whole separate kiln to barley use, maybe in the future if i can find a way to sell the bricks and after getting the rest of the farm set up. i will definitely make a new topic when i get to the point of setting it up. its going to be awhile. if anyone has any other idea on what i wana achieve, please chime in. ill probably have to make a custom insulation castings to go over the barrel to surround the stuff i want to firer. ill look into that bell method that was spoken of, but i dont want to do to many modifications from the original design. other then adding a couple things it should still be a cool traditional build whether i scrap the kiln idea or not. im excited to play in the dirt this next year.