Stove for a bomb shelter

I need to build a bomb shelter stove from scrap materials. At first, I wanted a simple one, but then decided on an additional afterburner. The firebox will have a removable lid; if you remove it, you can install a cooking pot. I'm also considering loading it with firewood, but then I won't be able to install a fire damper.

Bogdan,

I would recommend mixing some local clay soil with straw and try to use it to line your firebox and the afterburner - 5 cm thick layer would be good for the firebox. For the afterburner I would increase the straw to clay ratio  and could make it thinner. You will extend the life of the steel shell and will gain some thermal mass.

Cristobal Cristo wrote:Bogdan,

I would recommend mixing some local clay soil with straw and try to use it to line your firebox and the afterburner - 5 cm thick layer would be good for the firebox. For the afterburner I would increase the straw to clay ratio  and could make it thinner. You will extend the life of the steel shell and will gain some thermal mass.

Thanks for the advice. The firebox is 8 cm thick, so I don't think it will burn through, but it's 32.5 cm in diameter. Can I line the outside with clay? I wanted to make a protective screen out of a metal barrel to allow hot air convection between it and the firebox wall. I could fill that space with clay. But right now, the goal is to quickly heat the room. If I need to conserve heat, I can make a loop from the chimney along the floor and make a mass. What is an afterburner?

Cristobal Cristo wrote:Bogdan,

I would recommend mixing some local clay soil with straw and try to use it to line your firebox and the afterburner - 5 cm thick layer would be good for the firebox. For the afterburner I would increase the straw to clay ratio  and could make it thinner. You will extend the life of the steel shell and will gain some thermal mass.

Thanks, I figured out why it's necessary to insulate the firebox and afterburner.

Hello Bogdan, we are sending our care and respect from sunny North Georgia!  I love seeing your projects come together.  Whatever you build will be effective and easy on the eyes, I am confident.  
Slava Ukraine!
Rico

I'm preparing a stove. The firebox diameter is 32.5 cm, the firebox height is 55 cm, and the thickness is 8 mm.
The ash pan height is 26 mm.
The tunnel in front of the fireplace mantel is 40 cm long with glass. The tunnel dimensions are 23 x 23 cm. The firebox cover will be removable for easy loading of firewood and installing a cooking pot. A 33-diameter oxygen supply pipe will also be connected to the firebox. Oxygen will also be supplied through the fireplace mantel and the ash pan door. The firebox will be in a metal casing, into which I'll place 5 cm of clay.

Rico Loma wrote:Hello Bogdan, we are sending our care and respect from sunny North Georgia!  I love seeing your projects come together.  Whatever you build will be effective and easy on the eyes, I am confident.  
Slava Ukraine!
Rico

Thanks, Rico! Everything will be fine. I hope you're prepared for winter and have some firewood? As you can see, I have to invent new gadgets)))). But work allows me to warm up a bit and save on a psychologist))))).

If you line the interior of 325 mm pipe with 50 mm if clay mix you will end with around 220 mm of firebox diameter. With the height of 55 cm it should give you very satisfying burning quality. Firebox dimensions of my outside dry stacked cooker are 210x210x500 and it burns so well that I will be building a stove based on this design in my house soon.
For air supply:

-you can either provide it perpindicularly to the firebox on the firebox floor level (please also line the floor with clay - lighter mix with more straw will help to keep the fire hotter)

-or you could provide it from below, but you would need a heavy duty grill; after experimenting I found the grill version to be better burning my eucalyptus firewood which is very dense and produces a lot of coals that need more oxygen (similar to coal that needs grills in the heaters) to fully combust and turn into ash

I've been thinking about it for a long time, but I think I'll have to abandon the top-opening lid... It needs to be fairly airtight, preferably with flanges, but unfortunately, it's a complicated design for women if I'm not around. Of course, loading firewood from above is convenient, but functionality comes first. So the lid will be made airtight.

Cristobal Cristo wrote:If you line the interior of 325 mm pipe with 50 mm if clay mix you will end with around 220 mm of firebox diameter. With the height of 55 cm it should give you very satisfying burning quality. Firebox dimensions of my outside dry stacked cooker are 210x210x500 and it burns so well that I will be building a stove based on this design in my house soon.
For air supply:

-you can either provide it perpindicularly to the firebox on the firebox floor level (please also line the floor with clay - lighter mix with more straw will help to keep the fire hotter)

-or you could provide it from below, but you would need a heavy duty grill; after experimenting I found the grill version to be better burning my eucalyptus firewood which is very dense and produces a lot of coals that need more oxygen (similar to coal that needs grills in the heaters) to fully combust and turn into ash

Thank you! The air supply will be from the fireplace mantel, through the ash pan below where the cast-iron grates will be. Then the air supply will be below the chimney opening at the back of the firebox. Above the chimney opening, there will be a disk with a narrow, stainless steel corrugated pipe wound into a spiral with 3 mm holes. Unfortunately, I refuse to load wood through the top of the firebox, so I can't line it from the inside. The clay will be on the outside.

I will mix the clay with concrete fiber and compact it into the casing. The top of the casing will be open so that moisture can escape.

It's difficult to picture the entire device, but as long as you line it with your clay mix and make sure that the exhaust eventually leaves the bunker, then you are good to go!

Cristobal Cristo wrote:It's difficult to picture the entire device, but as long as you line it with your clay mix and make sure that the exhaust eventually leaves the bunker, then you are good to go!

I agree, it was even more difficult to imagine this design when I saw a piece of pipe in a landfill)))))

There's electricity, I need to go to work.

the process is ongoing

Bogdan,

Nice design.  I admire and applaud your resourcefulness.  I don't doubt that you are going to make this work.



I think that this thread has given you a lot of very good advice.  For my part, I agree that covering (almost burying) the whole assembly of internal stove components in clay is the right idea.  Partly to hold all those parts together, partly to seal any potential air leaks, and especially to get some good mass around the stove to store heat!


For what it is worth I tried a very simplified design of a biochar kiln that basically works on the same principles,  You can find it HERE:

https://permies.com/t/72466/Cheap-easy-mini-homemade-biochar


My little setup was just to see if I could in fact make biochar--and it worked flawlessly, if on an extremely small scale.  Obviously, your plan is for heat, but I don't see any reason that it would not work with maybe just a little adjustment.  For whatever it is worth, my kiln did not work very well on the first attempt,  I needed to drastically improve the airflow.  I don't this this is a problem for you, but I am merely expressing the warning to expect the unexpected.

And in case I have not already mentioned it, I just love that you are making this from spare parts laying around.  That part has to be my favorite--that you had to use your ingenuity.



Good luck and please let us know how things work out!

Slava Ukraini


Eric

There will be a dual air supply system to the firebox. The first is a 32mm pipe, the end of which is bent, perforated, and plugged. The holes point downward. One end of the pipe will be located in the ash pan and will draw air from outside, while the other end will be located above the chimney entrance. The second supply is through a corrugated stainless steel hose. One end will be located in the ash pan and will draw air from outside. Then, the hose will be wound around the vertical 32mm pipe, and the end of the hose will be wound in a spiral on the inside of the lid. The spiral has holes in it.

Eric Hanson wrote:Bogdan,

Nice design.  I admire and applaud your resourcefulness.  I don't doubt that you are going to make this work.



I think that this thread has given you a lot of very good advice.  For my part, I agree that covering (almost burying) the whole assembly of internal stove components in clay is the right idea.  Partly to hold all those parts together, partly to seal any potential air leaks, and especially to get some good mass around the stove to store heat!


For what it is worth I tried a very simplified design of a biochar kiln that basically works on the same principles,  You can find it HERE:

https://permies.com/t/72466/Cheap-easy-mini-homemade-biochar


My little setup was just to see if I could in fact make biochar--and it worked flawlessly, if on an extremely small scale.  Obviously, your plan is for heat, but I don't see any reason that it would not work with maybe just a little adjustment.  For whatever it is worth, my kiln did not work very well on the first attempt,  I needed to drastically improve the airflow.  I don't this this is a problem for you, but I am merely expressing the warning to expect the unexpected.

And in case I have not already mentioned it, I just love that you are making this from spare parts laying around.  That part has to be my favorite--that you had to use your ingenuity.



Good luck and please let us know how things work out!

Slava Ukraini


Eric

Thanks Eric, your stove design is excellent. I was just thinking about the need for charcoal to make a water filter. Thanks for the idea.

Unfortunately, the blackouts continue. Tomorrow, the power will only be on twice for three hours, so we need to make the grates and install the firebox and chimney pipe.

Bogdan,

You probably either don't have a generator or fuel or you would be using those to finish this project sooner?  This frustrates me as I am eager to see how this works out.  But really, my frustration is nothing compared to what you have to go through!  For whatever it is worth, I am sympathetic and fully on your side.


But even without, I think that you have a great project here to help you get heat to get through the winter on a small supply of wood.

I don't know if this matters or not, but my little kiln did show me a couple of principles at work that I did not anticipate.


#1  My paint can/soup can kiln put out a LOT of heat.  As in I was afraid I had it too close to the car!  Capturing that heat is about the perfect way to make things work efficiently--and you are on that!

#2  I had to get the oxygen mixture just right.  In my case that meant drilling extra holes in the outer paint can.  After I increased the Oxygen supply, the smoke completely disappeared and the flame shot up just like a rocket--hence the name!  And that flame was almost invisible.  Just be careful.

#3  This probably applies more to me than you, but the intense heat did a number on my components--which were pretty flimsy in the first place.  After a couple of burns, all of the metal (which is to say the entire device) started to rust incredibly quickly.  I assume that the intense heat started to oxidize the metal during operation and once a little rust started, its demise was inevitable.  I have heard that kilns like these can only operate for about 10 burns before the components succumb to the intense operating environment.  Yours is thicker I assume?  This 10-burn limit was specific to similar devises using barrels.  Are any of your components made from a barrel or similar type of metal?  Most of your components looked pretty beefy.  I don't know how long your devise will operate--it might very well work for a long, long time. But I know that the intense heat can do a number on metal.  And of course, you are using what you have laying around and you need heat now so of course use those items--but maybe keep an eye out for potential wear and tear.

Overall, amazing project with limited resources.  Great work!

Slava Ukraini


Eric

Greetings my favorite cousin, I know you stay very busy but please read this other thread, from Kharkiv. She has a workshop from Canadian group to help build mass heaters,  free for soldiers and civilians, you have a wealth of knowledge this group will appreciate.

Stay happy , it is always there for us, we simply must grasp happiness.  A wise man named Bogdan once told me...

Sorry, that was not my intention

Eric Hanson wrote:Bogdan,

You probably either don't have a generator or fuel or you would be using those to finish this project sooner?  This frustrates me as I am eager to see how this works out.  But really, my frustration is nothing compared to what you have to go through!  For whatever it is worth, I am sympathetic and fully on your side.


But even without, I think that you have a great project here to help you get heat to get through the winter on a small supply of wood.

I don't know if this matters or not, but my little kiln did show me a couple of principles at work that I did not anticipate.


#1  My paint can/soup can kiln put out a LOT of heat.  As in I was afraid I had it too close to the car!  Capturing that heat is about the perfect way to make things work efficiently--and you are on that!

#2  I had to get the oxygen mixture just right.  In my case that meant drilling extra holes in the outer paint can.  After I increased the Oxygen supply, the smoke completely disappeared and the flame shot up just like a rocket--hence the name!  And that flame was almost invisible.  Just be careful.

#3  This probably applies more to me than you, but the intense heat did a number on my components--which were pretty flimsy in the first place.  After a couple of burns, all of the metal (which is to say the entire device) started to rust incredibly quickly.  I assume that the intense heat started to oxidize the metal during operation and once a little rust started, its demise was inevitable.  I have heard that kilns like these can only operate for about 10 burns before the components succumb to the intense operating environment.  Yours is thicker I assume?  This 10-burn limit was specific to similar devises using barrels.  Are any of your components made from a barrel or similar type of metal?  Most of your components looked pretty beefy.  I don't know how long your devise will operate--it might very well work for a long, long time. But I know that the intense heat can do a number on metal.  And of course, you are using what you have laying around and you need heat now so of course use those items--but maybe keep an eye out for potential wear and tear.

Overall, amazing project with limited resources.  Great work!

Slava Ukraini


Eric

Eric, thank you. Thanks to your example, I'll maximize the oxygen supply directly to the fire. My weak point is the transition from the ash pan to the firebox, made from the wheel rims, right where the grates are. I'll think about how to reinforce this component. The firebox itself, I'm sure, is 8 mm thick. The lid will be installed with the convex side down, which will strengthen the structure. Regarding power outages, these few hours are enough for me to continue this project.

Rico Loma wrote:Greetings my favorite cousin, I know you stay very busy but please read this other thread, from Kharkiv. She has a workshop from Canadian group to help build mass heaters,  free for soldiers and civilians, you have a wealth of knowledge this group will appreciate.

Stay happy , it is always there for us, we simply must grasp happiness.  A wise man named Bogdan once told me...

Hi, Rico, I read the post you're referring to and I understand your concern. Believe me, the most important thing is that the author of that post is on this forum, where there's a wealth of information and excellent examples of rocket stove implementation. If specialists are involved in this process, they will choose the option that suits them best. War is a very cruel thing, and to make a decision, you need to make a choice and act according to a plan. I understand your concern, but people are in the process, and if this is happening in Kharkiv, there are plenty of engineers and technical specialists there who can properly apply the information from this site. I see the competent answers they receive, and the most important thing is for them to find a reasonable compromise in the construction of rocket stoves.

Thank you Bogdan, you are truly correct, I  feel sure they will forge ahead with the idea.   Best luck on the power grid, rico

The ash pan is ready and the grates are laid. Unfortunately, the 32-gauge oxygen supply pipe turned out to be too long. Tomorrow I'll install the firebox and chimney pipe and cut the air supply pipe to the required length so that the curved end is slightly higher than the chimney entrance and doesn't interfere with the lid. I also need to buy some thick rebar and secure the grates with it. There are rocket stoves, but I'll call mine a hookah stove.

I like the heavy gauge off the metal materials you are using. My concern in a bomb shelter if the whole stove tipping over and spilling burning coals on the floor. Scary!
Next concern is CO carbon monoxide. Hope you have a good hot, clean burn.

stove installation

Wow,

That’s a nice build there, good craftsmanship.


Eric

I installed the clay case, unfortunately it shifted, so the case did not fit evenly. In the future, I will figure out how to increase the mass.

Bogdan,

Very nice!  Almost done.

Can you tell me what the purpose of the curled piece is inside the burn chamber?

Eric

Eric Hanson wrote:Bogdan,

Very nice!  Almost done.

Can you tell me what the purpose of the curled piece is inside the burn chamber?

Eric

This is the oxygen supply pipe into the firebox, it goes down, passes through the ash pan and comes out at the very bottom of the furnace.

Ahh, got it!

work is in progress

I came across a good cover made of thick metal, I dismantled the old one and installed a new one, laid clay with straw and fiber in the chimney and around the firebox

The project is finished, everything works great.

Very nice!

I bet that stove is toasty warm.  How well does it hold heat after the fire is out?  Really, this is like a piece of bushcraft engineering turned art.


Eric