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The "Hermit's Hot Hog" - Timelapes of a Stove Build  RSS feed

 
Johannes Schwarz
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I would like to thank everyone on these forums for sharing and helping others.
After browsing through the RMH section I ended up with something called a Vortex Stove (More about the thing here: http://donkey32.proboards.com/thread/703/vortex-stove?page=1) which has some horizontal Rocket Action going on, but I guess is a wood stove and thus belongs here.

To give back to this community I wanted to share a timelapse-ish video of the build, to encourage people to experiment. If I, a priest and theologian in training, can do this, most of you will do much better still. So without much further ado, I present you with the "Hermit's Hot Hog"

 
Brad Hengen
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thanks for sharing!

looks nice.

I most liked how you formed the concrete pieces!!!   great ideas!

 
Bryan Nichols
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That's rad! Nice job on both the stove and the video!
 
Len Ovens
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Johannes Schwarz wrote:I would like to thank everyone on these forums for sharing and helping others.
After browsing through the RMH section I ended up with something called a Vortex Stove (More about the thing here: http://donkey32.proboards.com/thread/703/vortex-stove?page=1) which has some horizontal Rocket Action going on, but I guess is a wood stove and thus belongs here.


Thats a hard one. This is still a high mass heater with more in common with the RMH than an iron stove most people think of when they see the words "wood stove". Not that I want a flame war... but in my opinion, I think it is possible to build a high mass heater with no barrel that will be more efficient than the standard RMH. I am not so sure about the embedded energy to heat into the heated space part but the best use of radiated heat will be better with thicker walls than a barrel... and as such lower surface temperature. My personal opinion is that the closer the stove surface temperature is to body temperature the better (internal stove temperature should be really high on the other hand). The idea is to keep the temperature differential of the stove's radiating surface to outside of the home surfaces as low as possible while being comfortable. So the RMH vs everything else does not make so much sense to me as just MH to other comparisons.


To give back to this community I wanted to share a timelapse-ish video of the build, to encourage people to experiment. If I, a priest and theologian in training, can do this, most of you will do much better still. So without much further ado, I present you with the "Hermit's Hot Hog"


Great job! I would have made my heat storage more "Bell-ish", but your's has the advantage of putting more mass in a small area. It looks nice, burns nice... all good.
 
Lori Dorchak
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Lovely video! You make it look almost too easy!
 
C Jones
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I like it! Want to come build me one too ? Then make me one of those pizzas .  The fact that you can watch the fire is pretty nice too. That's one thing I  could wish were different on the standard type of RMH.

So if it's brand-new, maybe you don't have a good feel for how efficient it is yet? Any kind of comparisons versus say the standard metal box type of stove?   Or would anyone else like to venture and educated guess comparing something like that to a rocket mass heater, in terms of efficiency?
 
Julia Winter
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That is a beautiful video, and a lovely stove!
 
Johannes Schwarz
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Hello everyone and thanks for the kind words.

I posted the video a couple of weeks ago, so I was surprised to see a big spike in the vimeo view count this morning. I guess, this means it got cold wherever you guys are. Heating season is on

Len,
you are right. Looking at my exhaust temps, I could have increased the thermal mass and made the top section (which is one large bell) larger. On the other hand, my place is not very big and I will see this winter how I fare with the dimensions I chose. One of the reasons I did not go bigger, aside from over heating the place, was that I was not sure how much I could alter the plans I had, without it stopping to work (chimney draft and all). It was the first stove I ever built, so I mostly tried to stick to the things I knew were working in the original design.
As for the classification of the stove, this particular design shares properties with different types of stoves and I'm no expert. I put it here under wood burning stoves mostly because it burns wood and the category seemed to me more general, which might just be because I'm not a native speaker. But I see no problem with flame wars. They would appear fitting when it comes to stoves and "things heating up" is a good thing for the approaching cold season Here is how I would describe Trev's vortex design, my stove is based on:
The way the burn chamber is constructed there is some horizontal rocket action going on upping the temps.
The way the thermal mass  is constructed it is a masonry stove.
The way it looks on the burn chamber side with the glass door is like a wood stove.
The way it can be used is like a kitchen wood stove with its cook top and oven.
The way it behaves is like the Kachelofen (Grundofen  - ask google for pics, I did not get a proper translation. It is typical for Austria and southern Germany) I grew up with. It stores and radiates heat for 10-12 hours.   

C Jones,
well, if you live in a really nice place I could consider building one for you. Then again, if the place had palm trees, you would not need a stove But if you are half serious about the idea, talk to Trev over at donkey32. He has actually built several for other people and he is the real pro.
As for efficiency, I will know more after the winter. I made some temp measurements on my third burn with one of these laser thermometers, but it is off ebay and I'm sure it is not industry quality and might be off a little. Better and more meaningful stats I can provide after the winter. Here is what I noted down and recall:
Since I still lack a scale, I don't know how much wood I used in that burn but I would estimate it was:
20 pounds of really dry mixed wood (beech, birch, chestnut, stuff).
Half of the wood to start the fire. Half of the wood added after about an hour
burn time: about 2.5 hours
heat in the burn chamber (pointing in the fire) reaching 1700 °F
insulated walls of the burn chamber reaching about 1200 °F
top cook plate reaches about 830°F (water does get boiling quickly)
glowing coals: about 4 hours in. Burn chamber walls radiate 850 °F inside. A little wait and you have perfect pizza temps.  2 hours later it is bread time.
exhaust pipe temps right out the stove peak at 300°F (i also built a short cut for a better draft, which I use when kindling the fire) and go down to about 170°F. When the fire is out, I flip a lever to put the damper of the pipe to use.
surface of thermal mass reaching 180°F in some parts on top. 150°F in others. Since the surface is not smooth (like metal or tiles) but rough, it can be touched and leaned against, though during the hottest time of the cycle I would not press myself against it for too long
after 10 hours: thermal mass temp is at 110°F
after 12 hours: thermal mass temp is at 90°F
after 18 hours: burn chamber walls (inside) still radiate in the 90s. Thermal mass section has room temp (71°F)

I plan to experiment with a heat sink around the stove pipe to reduce heat loss through the exhaust.
One further modification I plan is a tube for secondary air in the top half of the burn chamber. The burn is clean as it is, but oxygen is always fun to add and should give even better efficiency burning all gasses. At least I think it will.
I don't think I need any of these improvements to make my place warmer (though we will see in winter - I'm in the alps at 4000 ft), but if these tweaks make the stove more efficient, they will save some wood.

Cheers

 
Len Ovens
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Johannes Schwarz wrote:Hello everyone and thanks for the kind words.

I posted the video a couple of weeks ago, so I was surprised to see a big spike in the vimeo view count this morning. I guess, this means it got cold wherever you guys are. Heating season is on


Someone brought it to our attention


The way it behaves is like the Kachelofen (Grundofen  - ask google for pics, I did not get a proper translation. It is typical for Austria and southern Germany) I grew up with. It stores and radiates heat for 10-12 hours.   


I always thought the defining part of the Kachelofen was that it was finished in tile (often with tiles made just for the heater). Check out This Video or her webpage.


exhaust pipe temps right out the stove peak at 300°F (i also built a short cut for a better draft, which I use when kindling the fire) and go down to about 170°F. When the fire is out, I flip a lever to put the damper of the pipe to use.


That is not a bad exhaust temperature... but, do be aware that pipe temperature and gas temperature will be different. Temperature measured by a probe in the middle of the gas stream will be higher than the pipe temperature. (at least that was what I found)


surface of thermal mass reaching 180°F in some parts on top. 150°F in others. Since the surface is not smooth (like metal or tiles) but rough, it can be touched and leaned against, though during the hottest time of the cycle I would not press myself against it for too long
after 10 hours: thermal mass temp is at 110°F
after 12 hours: thermal mass temp is at 90°F
after 18 hours: burn chamber walls (inside) still radiate in the 90s. Thermal mass section has room temp (71°F)


sounds perfect.


I plan to experiment with a heat sink around the stove pipe to reduce heat loss through the exhaust.
One further modification I plan is a tube for secondary air in the top half of the burn chamber. The burn is clean as it is, but oxygen is always fun to add and should give even better efficiency burning all gasses. At least I think it will.
I don't think I need any of these improvements to make my place warmer (though we will see in winter - I'm in the alps at 4000 ft), but if these tweaks make the stove more efficient, they will save some wood.


I would say something along the line of "use a CO alarm" when trying to reduce exhaust temperature, but if you grew up using mass heaters... you are probably aware of what to look for already. North Americans who are used to steel box wood stoves are much more at risk.
 
Johannes Schwarz
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Hi Len,

Over here we use "Kachelofen" improperly sometimes for what strictly speaking should be referred to as "Grundofen" which may or may not have tiles [=Kacheln]. In fact where I come from (or the era I come from) most of these types of stoves have few tiles, and if so, they have them mainly for decoration and that is why they kept the name "Kachelofen", I guess. What makes them special is not the shell but a heavy chamotte core. That is why I put "Grundofen" in brackets (which technically does not refer to the heavy core but the fact, that you light the fire "on the ground" instead of a iron grill atop an ash tray. A Grundofen does not have an ash tray). Aside from Kachelofen types that are Grundöfen, there are also types of Kachelofen that are all tiles (and thus certainly properly called so). But they are completely unlike a Grundofen, since they are relatively light and don't necessarily have to be built on the spot but are in principle (and some in fact) moveable. They are a type of wood burning stove with a metal fire box and no heavy thermal mass (thus no significant heat storage). They use the tiles for optics and heat transfer (instead of a metal design for example). The way you fire these two types of "Kachelofen" is very different. In a Grundofen you put all the wood, kindle the fire, and when all has burnt down (no more flames, just glowing coals) you have to close the door and lock it shut (no more air intake). You must not open it again or add wood. Depending on its weight it will take  hours to get warm on the outside. But then it gives off warmth for 12 to 24 hours depending how heavy the stove is built (well, technically, you must not open the door as long as there is the potential for wood gases mixing with oxygen over glowing coals...so once all is ashes, you would be fine). The second type of Kachelofen you heat like a regular wood stove. You keep the fire going and add wood.
A Kachelofen of the Grundofen variety with its layout of "heat channels" will need to be carefully planned (and usually built) by a professional to work. It can easily cost from 4.000 Euro to 10.000 Euro depending on it's desired heat storage capacity. But it belongs to the most efficient wood burning systems out there and is the "heart" of any house that has one. The untranslatable Austrian term "Gemütlichkeit" really is not imaginable without it in the winter season
The other type however may be bought pre-fabricated in a store if it is small and portable or assembled at home (by someone knowledgeable still).

It was mainly the price tag and the practical impossibility of getting a professional Grundofen builder to my mountain hut that made me explore alternatives and landing me here Now I'm happy with my hybrid combining different concepts. But I also did get a CO alarm, just in case there is an issue with the chimney airflow and I have gas coming the other way. I am after all not a professional. And what I was allowed to build here in Italy, would have required expensive certification by a chimney sweep in Austria. Stricter laws over there.
 
Len Ovens
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Johannes Schwarz wrote:
A Kachelofen of the Grundofen variety with its layout of "heat channels" will need to be carefully planned (and usually built) by a professional to work. It can easily cost from 4.000 Euro to 10.000 Euro depending on it's desired heat storage capacity. But it belongs to the most efficient wood burning systems out there and is the "heart" of any house that has one.

...

It was mainly the price tag and the practical impossibility of getting a professional Grundofen builder to my mountain hut that made me explore alternatives and landing me here Now I'm happy with my hybrid combining different concepts. But I also did get a CO alarm, just in case there is an issue with the chimney airflow and I have gas coming the other way. I am after all not a professional. And what I was allowed to build here in Italy, would have required expensive certification by a chimney sweep in Austria. Stricter laws over there.


In North America, it seems any masonry/mass heater would cost at least $10k to be legal (I would suggest Kachelofen as in the link I gave before would cost much more). The requirement of having someone certified, foundation modification as well as double skin construction pushes the cost up very quickly. I think this is the reason the RMH heater has been very popular with people as an alternative as it is mostly made from found materials (as were many of the Russian heaters before brick showed up). While there are some people working on it, for the most part, the RMH is not usable if certification is required either... so in many ways the masonry heater can be made for a similar price as the RMH where certification is not needed. In fact, I have seen a masonry heater made out of adobe brick that was made on site and not fired before building. The same clay mix then being used as mortar.
 
Thekla McDaniels
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Hi Johannes,

I enjoyed seeing that, and though it is not likely I will build one, I wonder if you had to use a special kind of cement in all those mixes.
 
Johannes Schwarz
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Hi Thekla,

the stone foundation of the stove is made with regular cement
the parts of the burn chamber are made with a special (and expensive) cast material (up to 2400 °F)
the fire bricks are layered with fire cement.
I guess half the video is mixing stuff
 
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