Ned, big question: Are you going to buy the book before trying to build one?
I'm also concerned that you won't be cobbing. Since part of your concern is that the exhaust gasses aren't able to vent and so will "backflow" into the residence, you need to consider the entire system. Since the purpose of the cob is to extract and store heat, and the characteristics of how it extracts and stores heat are different than those of water, your results will probably not match those in the "real world", and so your efforts will result in an incomplete and/or improper comparison.
The unit will not have cobbing on it, the cob serves little to no function as far as the firing of the unit goes.
2. You have a new car so to speak.
5. Some of the people whom have built the car have had failures with it
In other words, the cob is a heat sink for the furnace, with a few ounces of cob I can determine the rate it will absorb heat, once I know that I can use water rates to absorb heat at the same rate. I can also them alter that significantly and force the furnace to fail, record the data of the failure so you now know that information.
marina phillips wrote:
1. I am deeply concerned that you have so much criticism for a system you refuse to learn thoroughly about.
2. If you want to learn about something, do you not agree that it is best to go to the original source?
3.The personal connection you have with "three stoves" is merely an interpreter of the information in the book, which is in its fourth printing. If you want to avoid second hand information I suggest you buy the book.
4. I'll say it again: Beg, borrow, or steal the book. It's a little more than $20, including shipping.
5. Go ahead: break a system in to tiny parts, analyze those parts, and believe that the data about those parts yield more than the whole system. This, in my opinion, is the fundamental flaw of modern science - the inability and unwillingness to study a system as a whole.
6. I ask that you refrain from broadcasting your findings as a study of a rocket mass heater. You'll be studying a partially built stove vaguely inspired by a rocket mass heater, and to report your findings as the scientific testing of a rocket mass heater would be misinformation vocalized.
7. I believe these stoves have been safely used for about twenty years. I hope for someone else with more concrete knowledge to back me up.
8. Sure would be nice if Ianto Evans or Leslie Jackson could join the melee and offer some defense of their design and design process. I feel like it is them more than anyone else who is "on trial," so to speak.
By "failures" I'm assuming you mean having toxic gasses leak into the residence. I'm not aware of any such events. Can you document this claim?
FWIW, cob has an R value of 1.
To use your automobile engine analogy, I have no doubt you have a great deal of expertise in internal combustion engines. However, the RMH is an Wankel combustion engine (think the original Mazda engines). How much of your technical experience can be directly transferred from a four-stroke reciprocating piston engine to a four-stroke rotary engine?
Burra Maluca wrote:
RedNeck - is it possible for you to share the design you're going to use for the test *before* you build it so that folks here can critique it?
tel jetson wrote:
why don't you post about your results when you're done, NedReck? you'll avoid having to censor yourself and still maybe save some of us dirty hippies from our silly stoves. I'm sure you can easily get your internet argument fix over at the survivalistboards. what do you say?
I have tried to make it perfectly clear repeatedly, I have never seen one of these stoves. While that does not leave me at a loss for how they operate, much to the disappointment of many, it really is not that complex at all and has a great deal of potential.
I seriously doubt there is any reason at all to continue bothering with posting here at all. I thought folks were looking to get the RMH tested, they are not, they are interesting in talking about why it does not get done.
Erica Wisner wrote:
My only suggestion about your water-jacket testing setup:
Our experience with existing RMH's: They heat cleanly when used regularly in winter, when the mass is warmer than outside air. But a super-efficient model will be difficult or impossible to light cleanly when the mass temperature is below ambient air temperature. There are several tricks in related threads for how to safely pre-warm or boost the draft of a cold stove.
To make it a fair simulation of heating conditions, I'd suggest you pre-heat the water in the jacket before lighting, or use a draft-boosting option to bring the mass up above ambient temperature just as a home operator would with a masonry version.
Ernie and I operate on an annual budget of less than $15K most years, so we are limited in our own research to affordable materials.
With outside funds, we hope to build an example heater at local EPA-certified OMNI-Labs in Portland, Oregon. The plan for best practice (and a proposed building code for these devices) is to use firebrick for the combustion core and perlite/fireclay insulation, but original RMH standard (reclaimed and earthen) materials for the balance of construction.
Hope that helps you find more useful information for your testing project.
The cold start is certainly a problem that exist, however, I am fairly sure it can be overcome, well I know it can be overcome but my goal is not to modify it in such a way that you could not. In other words it needs to be done in such a way that does not involve anything more than a commonly discarded item one might find at any hardware store or if they posses the talent field manufacture using hand tools only. Best said, high tech workings from low tech parts.
Budgetary issues are of no concern for a small project like this to me or my departments, most of the high tech stuff the students are using now have controller boards that cost more than these stoves including a bit more industrial version I have in my mind to construct to confirm the fluid dynamics taking place inside the core unit. I do not plan on taking the start up temp below 32 initially so water is fine, if it is determined that feasible operation lower than that (aka in a vacation retreat that might be -10 on arrival and start up) and I can load the cooling tower through about 100 degrees.
From purely my own perspective, its not ready for testing yet. The experience you are having with them more or less not quite knowing what to call it is not a huge surprise. There are a lot of regulations surrounding how the combustion gases are handled. Having not seen your design I can not speak directly to it however, I can pretty much say that it violates several of them. In tech speak that would indicate it can not operate safely by established standards. With that thought in mind, the operation of it has risks and does need to be tended to and if it is, I would agree it is pretty low risk and as has been indicated, if one depended on the cob battery for heat when the unit was not in operation, any malfunction of operation would be noticed by the operator and easily corrected. Unfortunately it is a well established fact that there are indeed folks whom are not too bright in the world so when standards are developed a lot of the regulations come from “idiot proofing” the equipment.
I have no interest what so ever in seeking a patent. If Mr. Evans returns my call and we begin to communicate freely about it, we might be able to do some things that would improve the range of performance, widen the sensitivity to fuel, and provide the proof of concept in a fairly “idiot proof” manner. If he chooses to seek a patent, that will be his choice, some how from his writing in the book, I do not expect that is a goal of his either, though he might do so just to keep the technology free or very low cost (the price of the book) as a personal improvement to the world we all live in. My motives on the other hand are more selfish. As I said before, I am an INTJ personality type, I come alive when my mind is challenged and I have basically no creative side what so ever, mechanical thought is so intense for me I literally lose track of time. I can’t really explain it because I can not comprehend why all people are not this way as stupid as that sounds. I HAVE to know HOW this thing works and WHY it works that way to the point of obsessive compulsive behavior. I have likely slept under 10 hours total since I first signed onto this board.
I hope the energy I put into it helps you and others advance this in whatever manner you see fit, I seek only the stimulation it provides my brain and once I am convinced I have it pretty much all hammered out, I will indeed drop it like a hot rock and seek out another project to tax my mind. When I said mad scientist, you likely have no idea to just how close that really is.
Good luck in your efforts,
Erica Wisner wrote:You'd have to see one in operation to understand the problem and why I feel it's worth improving on this rather than starting over.
...Actually, I promise this is not required. I have studied the operation from many angles and am about 99.9% positive I have a fantastic visual developed from reviewing working designs, known failures and why those minute changes caused the failure. Fixing some of them is not as hard as one might think, but others may indeed prove to be very hard to eliminate.
Mr. Evans is not doing active research and development on these any more - calls tend to get passed on to me and Ernie quite a bit, or to a couple of other researchers down in California, depending on where the caller is from. So don't be hurt if he never does respond.
... With a grin I can assure you I will not be unhappy if Mr. Evans opts not to contact me. A lot of folks tend to change a lot while online, I am not one of them, I am just as hazardous in real life and there are more than a few whom consider my company unpleasing. While it might not be his reasoning, it happens enough I am quite used to it, I offend folks without intent and with intent both. I know "Donkey" has figured out a method to be tolerant of my misgivings and his wisdom and honesty have been quite helpful. If you and Ernie are capable of such tolerance, I am not opposed to discussing it with you as well.
You're right, he's not interested in a patent; he's developed a strong aversion to governmental agencies of many kinds, and to idiots. I suspect he kind of likes it that if you don't tend the fire, or clean out the stove, it smokes back at you.
... LOL Government is cool! It is a fantastic idea that has become distorted in so many ways the intent gets lost. Originally it was designed to protect us from itself and now it protects itself from us. Since I love ironic humor, I tend to get grand entertainment from the government machine all the while despising its existence.
He's been heard to predict that if we all just ignore the building code folks and refuse to cooperate, the whole thing will collapse under its own weight.
...I tend to disagree a bit. Nothing a power monger likes more than attention and if you fail to feed it, it tends to seek out more negative ways to get it.
But he grudgingly tolerates Ernie's and my attempts to wrestle with the lesser angels of building officialdom, and open a path for tested, coded, and permitted installations of these systems.
... I have driven a few things through certifications and understand a bit about it, most of it is really kind of stupid, some of it make sense.
Ernie is working on computer modeling for the fluid flows. He could use some help, if that's your thing. He's already heated test models to white-hot with illicit fuels, and attempted to build a half-model with an expensive and short-lived piece of Pyrex glass, as well as building hundreds of variations in more ordinary ways to try to replicate and develop remedies for the most common problems.
He's working with open-source software on our budget, building a wireframe and then going to run a fluid-flow through in another program to see if it can approximate the real results. I think we're surfing some aspects of fluid dynamics that are just not employed in most combustion devices, and I personally don't have a lot of confidence that the programs will have the right fluid dynamics on tap.
... Yes, I can indeed be helpful in more ways than one. The computer department head does not object to my ways and we both despise the political arena we work within at times. You are 100% correct in your assessment of combustion devices, I will expand more in a private manner only. I think you are mistaken in the programs abilities, like anything else with 'puters, input good, output good, input bad output bad. If my thoughts are correct which I have arrogantly already stated I think they are, it would be very easy to input poor data. I do not know Ernies "level" of education in these processes and when I speak to "level" it has little to nothing to do with formal education and everything to do with understanding.
I'm working more on the social compromises: just how easy does it have to be, for an early adopter to get interested? How much fuel savings, and how much convenience, will it take for the idea to progress beyond those early adopters?
... This "widget" offers nothing. Technology that fuels the capitalistic incessant need gets attention as it allowed one to take lots from others. Since it is simple to replicate, no matter how complex its fundamentals are, there is no effective way for one to capitalize upon it. Since it does more with less, it is indeed contrasting to capitol development. As stupid as it sounds, none of the industry that is involved would have any interest, it does nothing but reduce their capitol interest.
What is the most likely tragedy, and how can we mitigate it? And will our efforts pan out and allow us to make a decent living, or are we going to be stuck in 'maybe someday' forever, outmaneuvered by rival factions in the dazzling world of big building business?
...Depends on what a "decent" living really is doesn't it? In some distorted manner by and large this has come to mean "have more to feed more that have the most" which is a redundant double negative in my personal opinion.
I hope that actually seeing one burn gets you hooked thoroughly, enough to nail down some of these parameters before you find the next monster to reassemble.
...I do not need to see one, nor do I need to be "hooked" I am beyond that already. Please excuse the language, but this is some really cool f*** stuff!
Another useful tidbit would be to get some numbers on how cob absorbs heat so we can compare it with soapstone, concrete, etc. A lot of people try welding variations together, or want to build one of these with concrete, and I think they're in for unpleasant surprises if they don't account for the differences in density and heat conductivity.
...The cob really does not play an important role in the operation. It is a thermal storage device, a thermal battery if you will. Now when I say it does not play a role, that is not discounting it at all. Think of an electrical battery. They have a rate, a rate one should charge and a rate one should discharge. The cobs role may be best stated as a regulator of sorts. Instead of controlling the "voltage" going to it, the cob controls "how much voltage CAN go into it" which may buffer the processes taking place, I do not discount that at all. If I am correct, they would need regulation as they are very sensitive to change and the cob may very well "insulate" the process from those changes, obviously not in the terms of insulation typically understood such as keeping the heat in or out.
Speaking of no sleep, I better wrap this up.
Erica Wisner wrote:
well, now that everyone has chipped in about the technical details of how NOT to build a rocket stove...
anyone interested in seeing the current, inventors'-best-practice model put through some EPA tests?
... very much so and I hope the upcoming efforts can provide enough proof and interest to get just exactly that done along with performance curves.
I looked into the Kickstarter website, they say it's not a good fit for their site but good luck. Maybe we'd get farther with the how-to video we're producing, they seem to cater to arts projects.
The test I most want to see is how clean is the exhaust on a 'normal' system. We might be able to add 'modular' lengths of thermal mass to test several variations on the same system.
... the less expensive equipment used in standard tuning methods is fine for a close estimate, the problem does not revolve around that, this issue applies to lowering the exhaust temps too far, at that point the reliability of the software driven equipment fails to be accurate as it is not designed to operate outside of its parameters and there is a curve to its accuracy, if you get outside that curve, it is simply unreliable.
The second test I'd like to see is some data to figure out exactly how thick the cob should be, or an alternative masonry unit like bricks, if you are going to run the thing all day and have cushions on it.
Our experience is mostly with stoves that are run 2-6 hours per day on average, and where somebody removes the cushions if it gets too hot. Thicker masonry mitigates the 'hot spots,' but it is still possible to overheat a system if you use high-value fuels.
...though not on my to-do list, a thermal conductivity test on cob would answer this question, I do not think you will ever get rid of "hot spots" and would offer that this will always depend upon the materials and percentages used as well as the experience of the cob mason applying it. All the math capabilities and understanding in the world at my finger tips would not likely render as consistent or quality results as persons whom have made several of these and have developed a "feel" for the application.
Another test I'd like to see would be what strength is the draft under 'normal' conditions, and what range are the safe operating temperatures of these stoves. Ours works well when the thermal mass is warmer than outside air, but we have problems with a 'cold start' on a hot day.
... If my two of my theories on operation are accurate, this would be because of the density of the air affecting the engine that drives it as well as the thermal prime mover involved in acceleration of the gases through expansion, simply put the hotter the air the more it expands the more rapid the velocities, the warmer the air entering, the less the expansion itself becomes. this is why they operate over a narrow range and why if we define the parameters on it I think we can expand the range significantly with some fairly simple design alterations.
How long a heat exchanger would be allowable and still keep the exhaust above dew point at the chimney?
... This is hard to develop without a bit more info, one being accurate information on the pressures and after that, in order to keep it within the range of operation for approval, this number will be much higher than many folks want to hear. I can certainly prove that number for X temp at X relative humidity at X firing rate with X percent water content wood, but as soon as any one of those X's changes, the dew point will change as well. If you want to get a ball park for your own personal unit, take a good thermometer and cover the bulb completely with a cotton ball, wet the cotton ball with distilled water and put it into the exhaust stream for 5 to 10 minutes.
Would a bypass chimney-warmer be sufficient to promote good draft and prevent smokeback?
... I do not have a good answer for this one at all. I have an idea that might prove effective but I am not sure I could recommend it until we have found the range of operation and expanded it a bit as my thought is going to lend itself to effecting operation of the stove as I understand it and with my thoughts on the theory of operation, it might impact it a lot in a negative way. Would be a real pain to make one only to have done so in such a way it will not fire off the secondary burn.