What is the biggest, baddest rocket stove possible?

Any idea on the measured efficiency of a rocket stove:

For example, do we know what kind of cubic feet they will heat at a specific temperature differential using a specific fuel load?

What is the largest building that can be heated with one?

Is there anyone who has built a boiler with this system for use in transferring water through pipes installed into cement (radiant floor heating)?

I am impressed with the additional efficiency of these rocket designs, though I am still curious as to how they work fully - for example, how is it that the smoke doesn't exit the fuel feeding pocket - also, how do you deal with fresh air exchange in the structure - and - how do you keep insects from using the exhaust of it during the off season - or mice from crawling into the exhaust when the unit is simmering down?  Will screening this off (thinking yellow jackets and wasps) damper the exhaust enough to slow the flow and push smoke out the other end?

Do you have to eventually replace the combustion chamber?

I've watched some videos about this, but I would like to see this in action or build one myself and test it in a small temporary shelter...maybe some of you already have and know the answers!

Basically, (and I hate to be an annoying jerk, but..) all of your questions have an "it all depends" kind of answer..
Lets go through and look at what (some of) these things might depend on.

Kegs wrote:
Any idea on the measured efficiency of a rocket stove:

For example, do we know what kind of cubic feet they will heat at a specific temperature differential using a specific fuel load?

Up till now, there have been few to none fooling with these things with the skills, training and or desire to nail down that kind of  hyper-numerary specificity. Recently however, there have been some new arrivals who may be working on that question (and others) soon.
Though honestly, I'm of the opinion (and I'm certain that few here (if any) share my feelings) that these kinds of questions are HUGELY misleading and rarely (if ever) answer to the central issue, HEATING PEOPLE..

What is the largest building that can be heated with one?

What is the largest rocket stove that can be built?

Is there anyone who has built a boiler with this system for use in transferring water through pipes installed into cement (radiant floor heating)?

Yep.. There are a few folks working on it.

I am impressed with the additional efficiency of these rocket designs, though I am still curious as to how they work fully - for example, how is it that the smoke doesn't exit the fuel feeding pocket - also, how do you deal with fresh air exchange in the structure - and - how do you keep insects from using the exhaust of it during the off season - or mice from crawling into the exhaust when the unit is simmering down?  Will screening this off (thinking yellow jackets and wasps) damper the exhaust enough to slow the flow and push smoke out the other end?

Under the wrong conditions, with non-optimal stoves or too long benches, smoke DOES back up. I could get into the basic principles of the thing, but I'd end up sitting here FAR too long (for my good and my wife's patience) and you would have to read through a long rambling post.. In short, the classical explanation is chimney effect (or stack effect), which I don't entirely agree with.. The model doesn't quite fit, so I'd have to add "expansion engine" (wikipedia, gas laws), something loosely akin to the ram jet, though not as energetic.. Air exchange, like any other.. Leaky doors and windows usually, though outside air can be piped in..
I've known and loved several stoves that have been invaded by rats/mice/etc.. Build them well to minimise this kind of problem.

Do you have to eventually replace the combustion chamber?

What did you make it out of?

I've watched some videos about this, but I would like to see this in action or build one myself and test it in a small temporary shelter...maybe some of you already have and know the answers!

I highly recommend you build one in the yard or a shed somewhere. Some place fire and smoke safe where you can build a few failures as well as successes. Nothing like screwing up completely (in as many different ways as possible) to REALLY learn the ins and outs of something!

Donkey wrote:
Basically, (and I hate to be an annoying jerk, but..) all of your questions have an "it all depends" kind of answer..
Lets go through and look at what (some of) these things might depend on.

Thanks Donkey.

I am going to see what I can do and share when I get somewhere with all of this.

    Some of the biggest baddest rocket mass heaters go by an entirely different name. Many beehive kilns have been built over the centuries and the better designed ones have a wood feed tunnel similar to the extended doorway of an igloo. The better ones were built with a firebrick lining. The thermal mass was the kiln itself and its contents. One winter in Nanaimo British Columbia I heated a small house almost exclusively with my two electric kilns. A nice big wood fired one smack dab in the middle of the living room would have been far superior. Also Russian fireplaces use basically the same principle as a rocket stove. The primary difference is that they require quite a bit of expensive masonry work and they are more vertical in nature. Quite a few of these have been done on a grand scale and there is no reason why the same couldn't be done with less expensive materials.

Umm.. Actually, the BIGGEST difference between rocket stoves and the rest is the arrangement of the firebox.
High efficiency in terms of turning wood into heat is a good beginning, one where MANY others fail right out of the gate.
There are other methods of getting a good, efficient flame besides rocket stoves.. Just say'in that there is a difference in basic design here, can't call a Russian mass heater a "rocket stove" as the burn box works under different principles.
'Course, what happens AFTER you turn wood to heat is pretty much the same, which is what I think you meant.

dale hodgins wrote:
    Some of the biggest baddest rocket mass heaters go by an entirely different name. Many beehive kilns have been built over the centuries and the better designed ones have a wood feed tunnel similar to the extended doorway of an igloo. The better ones were built with a firebrick lining. The thermal mass was the kiln itself and its contents. One winter in Nanaimo British Columbia I heated a small house almost exclusively with my two electric kilns. A nice big wood fired one smack dab in the middle of the living room would have been far superior. Also Russian fireplaces use basically the same principle as a rocket stove. The primary difference is that they require quite a bit of expensive masonry work and they are more vertical in nature. Quite a few of these have been done on a grand scale and there is no reason why the same couldn't be done with less expensive materials.

    Russian fireplaces have a horizontal feed tube and will take somewhat longer to reach peak efficiency since firebrick rather than an insulated heat riser is used. Once these bricks are hot the process is identical, small quantities of wood burning with full draft for complete combustion followed by large thermal mass to absorb heat and low exhaust temperature. Some of the more elaborate Russian fireplaces include benches and sleeping platforms and because they are vertical these components can be extended to a second floor. Pretending that the concept is new works against attempts to gain widespread acceptance by homeowners and by building authorities. Why not sell the idea as an improvement on a tried and true technology that has been with us for hundreds of years? That's the route to acceptance that has worked for people building with Adobe and rammed earth.

Not sure if it is exactly a rocket stove or not as it is a Russian stove..not going to get into the above discussion..but it IS a highly efficient  form of heating which is certainly at least a first cousin.  This site has masses of information to chew on. At first glimpse they would appear to be more complicated to build, but now I'm not so sure..I am still looking for a multipurpose rocket stove.. heater, oven and water heater..and this seems to me to be a style perhaps closer to providing all of that.

It does call for brick rather than cob, but bricks can be made - not all require high firing temperatures if they aren't going to be used as an inner layer; people used to make chimneys  out of sticks and mud but those fires were not going to get as hot as these ones will. One thing about  using brick is that dimensions/proportions are a lot easier to identify and copy.

http://stove.ru/index.php?lng=1&rs=109

Wow, where to start. The names Russian fireplace, Russian stove...etc. I am thinking that the most well known ones from Russia would be the peasants ovens, starting with the old ones which are basically a brick oven from home made clay bricks (much like an adobe or cob oven) that has a flue to exhaust fumes out of the house (some of the really old ones don't even have that) and lots of mass. These were built as a cooking device in a separate cook house... the family then moved into the cook house in the winter to keep warm. These are not at all like a RMH as far as the method of combustion is concerned. These ovens were redesigned (during a fuel shortage ) And a remote fire box was added as well as the ability to direct flue gas through the base to better act as heater. Still not much like a RMH but quite efficient none the less. The Finnish contraflow heater (which has also been called a Russian heater.... European heater might be more accurate) is a vertical heater and does use much the same principles as a RMH. Properly fired from top down, the flue gasses go up through an insulated heat riser which is smaller than the fire chamber to complete combustion before being directed down through the mass and out. The only difference really is that it is a batch burner and so the bottom of the J has been moved to make it more convenient to load. The difficulty with them is operation... people in N America see them as a "fireplace" and try to use them as such. They are meant to be loaded, started burning from the top so that the fire gets hot fast and have the door closed during operation. They have the potential to be as efficient as a RMH but are built to code... that is you can get a permit to install one. As such the exit temp has to remain high enough to keep a chimney drawing happily. The riser tube/vent is generally 4in x 18 in. about the same area of a 10in RMH so not as big as it sounds. Because there is no J the riser is shorter too... though I think the riser is also shorter due to ceiling height restrictions as well and the rocket effect may be a little less pronounced as a result. (not saying how the rectangle shape of the riser effects things) The European heater could be made to have a lower exhaust temp and wall vent... But I am not sure I feel that comfortable doing that even with a RMH.

As with everything, there are compromises. The European heater does not give quick heat like the barrel on the RMH, but is meant to be refired before it gets so cold this is needed. The RMH can be much cheaper to install using found materials ... but then if you are not too worried about code, so can the brick heater. The RMH allows varying the amount of firing as you go. The brick heater needs less attention, but a good idea how big a batch needs to be considering the temp of the heater and the temp of the room... something that can be learned. Both heaters need a general relearning of firing skills in a world where fire places and iron stove are the norm.... they are not the same.

   I used a Russian fireplace in Ontario. The fire burned white-hot and sucked like a jet engine. I went on the roof and the exhaust was not hot enough to burn my hand. The operation was quite straightforward and I'm sure a monkey could learn to operate one. When the firing was complete a handcrank shut off the upper vent and a small steel door sealed up the feed tube which prevented the heat from going up the chimney.

My daughter had a masonry heater built between the living room and dining room areas about a dozen years ago.  They live in Nova Scotia and it's the only source of heat for an old three story house. 

They have a "fireplace" option on one side (they usually use the  other side which is the more efficient side although you can't see the fire)  and they have a bench built into part of it which is wonderful to snuggle into. The are quite content and happy with it.

dale hodgins wrote:
   I used a Russian fireplace in Ontario. The fire burned white-hot and sucked like a jet engine. I went on the roof and the exhaust was not hot enough to burn my hand. The operation was quite straightforward and I'm sure a monkey could learn to operate one.

A monkey yes... the average "know it all" Wood burning N American? Read some of the comments by some of the masons who build these things (most of European background) and almost 100% of their call backs are people using them like fireplaces or iron wood stoves even though they have been shown how they work and provided with written instructions etc. I agree, they are easy to use... easier than the average iron wood stove in my opinion. Some people are just too smart for their own good.... (no one who reads these forums I'm sure ... he says remembering all the dumb things he's done...)

So how about a rocket stove that can heat 4 stove top burners and maybe even an oven, but with a single fire, perhaps using valves to shut off the unused portions, anyone seen something like this?

please read the darn posts. in the last two days i have answered most of your questions twice.
the space any stove will heat depends on the layout of the house.
same goes with any furnace; you think your forced air would heat much if it only went to one room?
this forum has pages and pages of answers you do the work and go look.

Glenn Koenig wrote:So how about a rocket stove that can heat 4 stove top burners and maybe even an oven, but with a single fire, perhaps using valves to shut off the unused portions, anyone seen something like this?

Here's a link to a stove similar to what you are inquiring about.

http://donkey32.proboards.com/index.cgi?board=discuss&action=display&thread=11

It's a great board, some extremely knowledgeable folk over there, and very helpful.