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Rocket mass heater plus a Russian masonry heater

Rivenfae Wolf


Joined: May 20, 2012
Posts: 16
Location: Missouri
My partner was wondering if anyone has gone out and tried combining the good elements from both the rocket mass heater, and the Russian masonry heater (I hope I have the term right)? If so what was the out come. If not does anyone think they might work together? My partner wants to try combining the two, but as he has been looking online to see if anyone combined them before so he doesn't make any mistakes that could be avoided. As the house we are building is a dome which should be fairly easy to heat we don't want something that will "burn us out" of it.


Been there, Seen that, and have the post cards to prove it.

Be Well, Be Safe, and Blessed Be...

http://rivenfae-wolfwoods.blogspot.com/
Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
other than the RMH is the same without the need for special bricks and tiles. I think that yes it could work. a few sleeping platforms and benches might be practical.

Perhaps your partner should come by permies and do a little reading I know someone has done some sort of experimentation and put it up around here.


Need more info?
Ernie and Erica
Wood burning stoves, Rocket Mass Heaters, DIY,
Stove plans, Boat plans, General permiculture information, Arts and crafts, Fire science, Find it at www.ernieanderica.info


K Nelfson


Joined: Nov 07, 2012
Posts: 124
As far as I can see, RMHs are an inexpensive (somewhat dodgy) subset of masonry heaters. I spend a lot of time doing things cheaply, so it's good to have RMHs as an option. By dodgy, I mean that there are lots of people on the internet who have made conceptual errors in describing their stoves. So just take it all with a grain of salt.

Some of the features of the two stove types are merely customary. Example: the mass of either stove could be cob or fancy stone---doesn't matter.
Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
I love it when folks insult a tech and use the internet as an information source that is supposed to be trusted to be accurate.

the internet is dodgy, its supposed to be dodgy, and then distilled in the keen mind into useful information. kinda like normal conversations with people.
K Nelfson


Joined: Nov 07, 2012
Posts: 124
Ernie Wisner wrote:I love it when folks insult a tech and use the internet as an information source that is supposed to be trusted to be accurate.

the internet is dodgy, its supposed to be dodgy, and then distilled in the keen mind into useful information. kinda like normal conversations with people.


Huh? Most sources are not to be completely trusted, particularly when the barrier to publishing is having an opinion. I've found the interwebs to be particularly variable. Some is really good, some is just terrible. Aprovecho lab has some really great pubs. Youtube has a series of videos of questionable RMHs. I was just underscoring the need to think critically but it sounds like you've figured that out, so let's get back to the point.

I don't think there's any insult in my previous response. There's nothing wrong with the RMH concept in particular. In the right application, it's right. But there's good research on this topic and there's several things that the RMH concept misses. Obviously, the RMH concept does not have fatal errors because so many people (even me) have built these and had some measure of success. But let's be a tiny bit critical and acknowledge that masonry heaters are a more thoroughly vetted design that include many features that RMHs lack.

So, from the top, the features of a masonry stove:

1. Small "airtight" firebox that gives you control over the burn rate via air input instead of blocking the exhaust
2. Fire is built on a grill to hasten the burning of coals
3. Complete combustion of wood gases prior to exhaust entering the flue
4. Long and convoluted flue acts as a heat exchanger but is sized so that there is still an adequate draft
5. Poorly-conducting thermal mass

The features of a RMH, as far as I can see are:

1. Combustion chamber has J shape
2. Insulated vertical combustion chamber
3. Convoluted flue
4. Poorly-conducting thermal mass

There's nothing wrong with the RMH concept. In practice, however, a vertical tube does not always serve as an ideal secondary combustion chamber. Most efficient designs where measurements of fly ash and other polutants are MEASURED include a catalytic stage, baffle, or some other way to ensure secondary combustion. Now I suspect that RMH builders have managed to choose the size of the combustion chamber so that it works. I mean, the right diameter, the right length, all that. If you study the effect of hot fluids in a column, you'll find that the standard models includes a factor that describes the uniformity of the fluid in each cross-section of the flue. (That same model includes a factor of height cubed, which shows the power of the draft in a stove.) If the combustion chamber is the right height and radius, the temperature of the gasses is probably relatively uniform and the whole system works. I suspect that if a RMH was made for a much larger building it may not work as well.

The convoluted flue and thermal mass are obviously where there's the most overlap between masonry heaters and RMHs. Stone is a poor conductor of heat so it is probably comparable to cob but I couldn't find a source that included the thermal properties of cob. And it probably depends on the amount and type of fiber, so maybe it varies too much to put in a reference book. Anyway, the amount of thermal mass and slow conduction are important.

The airtight firebox is important and most RMHs I've seen have it by accident. This is important because you want to control the burn rate. Somehow, I've never heard of anyone discussing this issue for RMHs... I've noticed that lamps, fires, candles, etc, burn dirty when they burn unchecked. A wood stove will smoke if it burns so hot that the draft pulls unburned wood gas out of the secondary combustion chamber before it has a chance to burn. Not hearing about this issue in RMHs makes me wonder....

BTW, a properly managed fire will have very little smoke. This is true for an open camp fire or a fancy wood stove. In this state, the stove may make the room uncomfortable warm or burn the fuel too quickly. However, most stoves can be made to burn without smoke.

On the whole, there's a lot of overlap between the two types of heaters and they both have their place. My criticism of RMHs include

1. There's a lack of measurements to back up the many claims of perfection.
2. There's a rich history of burning wood and RMH enthusiasts generally don't seem to be aware of the alternatives
2. Everything has pros and cons, including RMHs. The cons are equally important when you're making big decisions about your house
3. Stadium enthusiasm makes me nervous.

So, I hope that's all on topic and not offensive. Sometimes the typing comes out a little strong.

Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
it just struck me as ironic. the word choice.
I personally test what i see on the net or in books or any other publication. it keeps me from destroying things i dont wish to loose. my life being the first.
Joe Braxton


Joined: Mar 24, 2012
Posts: 233
Location: NC (northern piedmont)
    
    9
If you think all RMH have J tubes, I'd point to this - Kind'a long, but worth it.

http://donkey32.proboards.com/index.cgi?board=experiment&action=display&thread=113

Looks to me like a proper masonry heater with a rocket core. What do you think?
K Nelfson


Joined: Nov 07, 2012
Posts: 124
Joe Braxton wrote:If you think all RMH have J tubes, I'd point to this - Kind'a long, but worth it.

http://donkey32.proboards.com/index.cgi?board=experiment&action=display&thread=113

Looks to me like a proper masonry heater with a rocket core. What do you think?


So interesting. Even has O2 measurements. thanks for posting.
Rivenfae Wolf


Joined: May 20, 2012
Posts: 16
Location: Missouri
Joe Braxton wrote:If you think all RMH have J tubes, I'd point to this - Kind'a long, but worth it.

http://donkey32.proboards.com/index.cgi?board=experiment&action=display&thread=113

Looks to me like a proper masonry heater with a rocket core. What do you think?


Thanks! My partner is practically drooling over that link.
Balint Bartuszek


Joined: Dec 23, 2012
Posts: 56
Location: Hungary
What part of the " Russian masonry heater" you want to include?

Perhaps the open-able flue short cut, may be of limited use. Or the long, in the wall flue, but that is just as much rmh as Russian heater. And while a box feeding is convenient to operate, is hard to do right.
Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
Today 09:39:09 Comment

its a bell stove; not a rocket. it is however a good design. if you like it get hold of peterburge he's a great guy
Rivenfae Wolf


Joined: May 20, 2012
Posts: 16
Location: Missouri
Balint Bartuszek wrote:What part of the " Russian masonry heater" you want to include?

Perhaps the open-able flue short cut, may be of limited use. Or the long, in the wall flue, but that is just as much rmh as Russian heater. And while a box feeding is convenient to operate, is hard to do right.

the wall flue is what he was looking to incorporate into the RMH.
Joe Braxton


Joined: Mar 24, 2012
Posts: 233
Location: NC (northern piedmont)
    
    9
Rivenfae Wolf wrote:Thanks! My partner is practically drooling over that link.


You're welcome. Be sure to look around there good, there are several really nice looking designs in process.
Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
make sure they have been tested in use for more than a year. not tinkered with the whole time. That is if you are putting it in a house.
Balint Bartuszek


Joined: Dec 23, 2012
Posts: 56
Location: Hungary
Rivenfae Wolf wrote:
the wall flue is what he was looking to incorporate into the RMH.


That should be no trouble.
Kirk Mobert


Joined: Jan 07, 2011
Posts: 130
Location: Point Arena, Ca
    
    2
Ernie Wisner wrote: its a bell stove; not a rocket. it is however a good design. if you like it get hold of peterburge he's a great guy


Actually, it's a Rocket-Bell-Stove..
His heat riser is the oddest thing I've ever seen as a "rocket stove", but after a good deal of consideration, I gotta include this one in the family..


Build it yourself, make it small, occupy it.
Kirk Mobert


Joined: Jan 07, 2011
Posts: 130
Location: Point Arena, Ca
    
    2
K Nelfson wrote:

There's nothing wrong with the RMH concept in particular. In the right application, it's right. But there's good research on this topic and there's several things that the RMH concept misses. Obviously, the RMH concept does not have fatal errors because so many people (even me) have built these and had some measure of success. But let's be a tiny bit critical and acknowledge that masonry heaters are a more thoroughly vetted design that include many features that RMHs lack.


Yep, that's one of the things that I do.. (I'm Donkey, by the way...) I've ALWAYS been highly critical of my own babies (and others), highly critical of the rocket stove concept. I came in as a dedicated skeptic, I've been won over by a ton of happy facts. So, I'll address your concerns and mis-understandings one at a time.

There's nothing wrong with the RMH concept. In practice, however, a vertical tube does not always serve as an ideal secondary combustion chamber. Most efficient designs where measurements of fly ash and other polutants are MEASURED include a catalytic stage, baffle, or some other way to ensure secondary combustion. Now I suspect that RMH builders have managed to choose the size of the combustion chamber so that it works. I mean, the right diameter, the right length, all that. If you study the effect of hot fluids in a column, you'll find that the standard models includes a factor that describes the uniformity of the fluid in each cross-section of the flue. (That same model includes a factor of height cubed, which shows the power of the draft in a stove.) If the combustion chamber is the right height and radius, the temperature of the gasses is probably relatively uniform and the whole system works. I suspect that if a RMH was made for a much larger building it may not work as well.


You ARE on to something here.. What gets a rocket stove done "right" is well proportioned internals. A bit like Rumford fireplaces in that proportions are everything, well, almost everything, in the case of Rocket Stoves you MUST have good insulation.

The convoluted flue and thermal mass are obviously where there's the most overlap between masonry heaters and RMHs. Stone is a poor conductor of heat so it is probably comparable to cob but I couldn't find a source that included the thermal properties of cob. And it probably depends on the amount and type of fiber, so maybe it varies too much to put in a reference book. Anyway, the amount of thermal mass and slow conduction are important.


Yep. Unlike masonry heaters (and pretty much all other stove types) , rocket stoves de-couple the act of burning the fuel from the act(s) of using the heat. This is an important distinction that is often missed and gives rocket stoves a far greater level of diversity of use and/or diversity of morphology that other stoves.

The airtight firebox is important and most RMHs I've seen have it by accident. This is important because you want to control the burn rate. Somehow, I've never heard of anyone discussing this issue for RMHs... I've noticed that lamps, fires, candles, etc, burn dirty when they burn unchecked. A wood stove will smoke if it burns so hot that the draft pulls unburned wood gas out of the secondary combustion chamber before it has a chance to burn. Not hearing about this issue in RMHs makes me wonder....

BTW, a properly managed fire will have very little smoke. This is true for an open camp fire or a fancy wood stove. In this state, the stove may make the room uncomfortable warm or burn the fuel too quickly. However, most stoves can be made to burn without smoke.


You will notice that while most stoves can be made to burn cleanly, they tend do it with their stops open wide. The key is the right amount of air, too little and the fire will smolder, too much will cool the flame with unburned ballast gas. The downdraft (Evans style) rocket stove feed creates a balance between proper air intake and good placement of the fuel. The small firebox, tightly filled with wood allows just the right amount of air over the wood, which is held (by gravity) at the best position for combustion during more of the burn cycle.
Rocket stoves do indeed achieve "secondary burn", they just do it very early and with one breath of air. There is something called a Peter Channel that seems to help by separating out a small channel of air to the front (downstream), of the flame. This cleans up a rocket stove like nobody's business..
Also, the insulated burn works are critical for clean burn. The inside of a well built rocket stove tends to hover around 1200 deg F. which is practically unheard of in any other stove. Sustained high temps, plus the RIGHT amount of air, plus a good deal of turbulence, equals a sustained level of extremely clean burn.

One thing that is a bit of a pet peeve for me: Catalytic converters were invented to solve a FATAL PROBLEM with air tight stoves.. Somehow, some people see them as some kind of great invention.. I see them as an unfortunate but necessary REPAIR to an unavoidable issue in a poorly designed machine.

On the whole, there's a lot of overlap between the two types of heaters and they both have their place. My criticism of RMHs include

1. There's a lack of measurements to back up the many claims of perfection.


To be fair, thus far the whole rocket stove thing has been done by a bunch of us hairy, backyard tinkerer types.. These stoves have tended to be what I term Hippy Builts, made of mud and trash, by guess or by golly. We really didn't know what we were doing as it hadn't really been done before, there were no plans, sometimes they worked, sometimes they didn't and only (relatively) recently have we figured out exactly why. This is all changing now, because of the work of a list of tinkerers, DIY-ers, freaky die-hards and others..
If you want to see the journey of someone doing some serious experimentation and taking careful measurements, read this thread by peterberg.

2. There's a rich history of burning wood and RMH enthusiasts generally don't seem to be aware of the alternatives


Thats really up to each individual.. Too much of a generalization there, mate.

2. Everything has pros and cons, including RMHs. The cons are equally important when you're making big decisions about your house
3. Stadium enthusiasm makes me nervous.

So, I hope that's all on topic and not offensive. Sometimes the typing comes out a little strong.


Thanks for your post.. It's given me an opportunity to vent a little. I'll be glad to expand if needed on any of these topics, or discuss more that has yet to be covered.
For now I gotta go, time is late and I gotta work.
K Nelfson


Joined: Nov 07, 2012
Posts: 124
Kirk, Thanks for the response. I've learned a lot from this thread. Looking forward to reading more on the other forum referenced.

I've built a few small rocket stoves. The first two were a complete disaster. The third I got to work well enough to evaporate about 15 gal of maple sap into syrup. But it was by guess and golly, which is expensive (time, money, etc). I hope I'll have some better luck after learning more from these links.

Sorry, this has all been a little off topic. What was this thread about again? Oh, combining the two types of heaters... After the discussion, I'd avoid combining features without testing.
Kirk Mobert


Joined: Jan 07, 2011
Posts: 130
Location: Point Arena, Ca
    
    2
As to combining the best features of these stoves: as long as the combining happens downstream (that is AFTER) the burn unit, there should be no difficulties.
One of the nicest modifications to rocket stoves has come from the Russian stove tradition, the Bell.
 
 
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