Trying a RMH

Greetings from Spain . I'm trying to build a rocket mass heater and would like to make some questions. I do not control the English and I write this with the help of an automatic translator I hope it can be understood by English speakers.
It is a J tube with firebricks all the way , keeping constant dimensions 17x17 cm, 121 cm height in the chimney ( from the top to the bottom ), height of the feed tube 33 cm and I have also tested with 44 cm ( from the top to the bottom ) , burn tunnel length of 33 cm (excluding common areas of supply and exhaust ) . A barrel of 120 L covering the chimney , a barrel of 200 L on the previous , with 6 inches of clearance between the chimney exit and barrel. Horizontal exhaust 2.5 m with 20 cm diameter (4m more but I have not yet ) . It is all mounted temporarily abroad.
Everything works fine, but the fire tends to go up the sticks up in the feed channel , generating problems of wood smoke that heats but does not burn , especially in times of full load and at the end of burning . With timber repositioning solves the problem . Is this normal behavior in a RMH ? Does my construction defects?.
There are some small problems at start because the smoke was initially determined to climb the feeder instead of the correct path. The fix introduced earlier a newspaper burning in the background burning channel, initiating the flow of gases in the right direction , or once lit the fire power cover the mouth and within seconds the flames properly oriented . I think this situation is given in cold start because the air temperature at the inlet is the same as at the start and not naturally generates the correct trend in the flow , I hope to build the final installation this problem disappears .
Not very ethical post links to other forums, and please excuse me for that, can view photos of the project at this link http://www.paleoforo.com/t3412-rocket-mass-heater # 37742
I thank you for all the knowledge you kindly dumped here and thanks in advance for your answers.

You did not describe your stove pipe/chimney pipe. This is required in order to get a good draw. Lack of a good draw from the chimney is creating the problem of the flame crawling up the sticks.

Thank you for your quick response, but I do not understand you completly. The translator is not the ultimate solution If I understand you well, you ask me for the dimensions, the J tube feeding is 33 or 44 cm, i'm trying whith they both , 33 cm combustion tunnel, riser 121 cm, all with a constant cross section of 17 x 17 cm. If you need any other information, let me know. Regret language problems. Thanks again.

I'm asking about the exhaust which should be routed into stove pipe and then up through the roof of your house. At the ceiling of the room, it must be changed to a double walled chimney pipe for safety reasons.

If you do not have your rocket heater connected to some sort of stove pipe which goes up higher than anything else around, it is probably the reason the fire is crawling up the wood in your feed tube.

When I start a fire in my unit, I put a fire starter 1/2 in the middle of the burn tunnel. This gets the draft going in the right direction.

My installation is not interior, it is temporarily working outdoors for testing. The exit gases after barrel , is horizontal pipe of 20 cm diameter and 2.5 m length
My problem is that the flames go up the wood when fully loaded

The exit gases after barrel , is horizontal pipe of 20 cm diameter and 2.5 m length

Turn your pipe vertical and see if you still have the problem.

Aurelio Ape : O.K., you have made it clear you are still Testing your Rocket Mass Heater Outdoors !

As Soon as you Add a Barrel over your Heat Riser, you need to add a vertical Chimney right off of the RMHs Manifold ! (Add a barrel, add a Vertical Chimney )

This helps in Two ways, ONE - You Immediately get to see if Your system is going to work/Draft.

Two - You immediately know where the problem is! If Things greatly improve with the Separation of the Rocket burner from the Horizontal chimney, and connection
of the vertical Chimney, than you Know the Problem is NOT the Burner core !

If it does not get a lot better immediately, then your problem is in your Rocket Burner or in the manifold. The Manifold is where the Rockets Hot exhaust gases Change
Direction from falling vertically down the inside of the barrel, and turn at right angles to flow into the Horizontal ducting of the Thermal mass !

This Should Stop The wood in your Feed tube from burning up and out of that opening! IF it does not stop the Burn Back / Smoke back, Try positioning a fire brick
over the Feed Tube opening to reduce AND redirect to flow of air directly at the wood being burned! Multiple small sticks of very dry wood is better than fewer large
sticks !
Your outside chimney should be at least 1 meter taller than any near object !

Good Luck, Go with God ! And remember as soon as you add a Barrel and a vertical chimney ! Big AL !

I have big problems with language. A picture is worth a thousand words. This is my RMH. Starts well, runs well, the gases circulate well, the drum is heated and the exhaust pipe also, but with full load, the flames burn back go up above sticks and generating smoke .

Air hole in bottom of fuel feed tube.


Oh I see now, (2) barrels, one 30 gal. as heat riser, & one 55 gal. for the outside shell.

james beam

Hola Aurelio! No pongas esto en el traductor automático, que te lo explico en español

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Hello Aurelio & co.

Here it comes another spaniard to help if possible (thanks to Allen who said me about the languaje problem). Not very good at english writing, you know, but at least I'll be able to say it right in spanish
I'll try to explain you in spanish what the fellow friends are talking about.
I'm doing it right here instead of using personal message just in case some other spanish speaker should be reading.
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Hola Aurelio!

Un compañero que me estuvo ayudando desde aquí (Allen) me ha pedido que te cuente lo que seguramente te está pasando y que es lo mismo que me pasó a mí hasta que entre él y otros me fueron encaminando:

Una vez que tienes montada la "cámara de combustión", y llega el momento de poner el bidón exterior, comprobamos cómo la velocidad del tiro disminuye mucho, y provoca que parte del fuego y el humo vuelvan hacia atrás por la "boca" de la estufa. Yo pensaba (y supongo que tú también) que la fuerza de la "bomba" de succión que provoca el tiro interior (heat riser) junto con el enfriamiento rápido de los gases al pasar junto a las paredes del bidón bastaban para tirar con fuerza de los gases en la dirección de la salida, pero la realidad es otra, y ésto sólo funciona así si se dan ciertas condiciones que no se dan tan amenudo (cuestiones de presiones de aire que se ven afectadas por diversos factores como la dirección del viento, cercanía de tapias o tejados que modifican las corrientes de aire, etc). Así que la REALIDAD es que NECESITAS CHIMENEA para probar el sistema, y necesitas que esta chimenea suba cerca de un metro por encima de cualquier otra cosa.

La manera habitual de comprobar si la estufa en sí misma está bien hecha es conectar directamente a ella (en lugar de los tubos para los bancos) un codo o "T" y una chimenea vertical que suba por encima de cualquier obstáculo cercano (en mi caso era una tapia y un tejadillo, luego te enlazo a las fotos). Si al conectar la chimenea todo vuelve de nuevo a funcionar "como un cohete" sabrás que la estufa está bien hecha, y podrás seguir probando las conducciones horizontales tras las que tendrás que poner, una vez más, la chimenea. Si ni siquiera con ese tubo vertical funciona correctamente entonces será cuestión de la cámara de combustión y tendrás que ver cuestiones como escapes (el aire que se cuela por las rendijas entre los ladrillos es una faena) o el diseño de la zona del "embudo" para conectar con los tubos.

Allen también me pidió que te sugiera el uso de un ladrillo (o similar) para tapar parte de la boca dependiendo de la cantidad de madera que tengas quemando. Regular la entrada de aire es clave para una buena combustión y yo (que llevo sólo un mes más o menos usando la estufa, todavía en proceso de construcción) al principio no le prestaba demasiada atención a esa cuestión que resulta vital tanto para la buena quema como para el aprovechamiento del calor.

Espero que con una chimenea directa te funcione de maravilla, ya nos irás contando.

Ah, aquí puedes ver el hilo en el que yo he ido comentando la construcción de la mía, está en inglés, por supuesto, pero podrás ver las fotos del proceso. Fíjate en que todo vuelve a funcionar una vez que pongo una chimenea más alta que el tejadillo junto al que monté la estufa. Ahora va de maravilla!
my own RMH building process thread here
Un saludo desde León

Manuel


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Dear english-spoken friends: what I've told Aurelio is just what you said (as previously you did to me with just the same issue with my own RMH making) about the need for a chimnney and how to use a temporary one just next to the barrel to test the stove itself. As Allen asked me to do I've mentioned the use of a brick to adjust the air intake and improve the burning. Excuse me for not translate it all again to english now, but I'll do if you feel I should do it.

By the way: my own RMH it's working pretty good. It isn't yet finished, but mornings are far more confortables now at home thanks to your kind support I'll post some more photos of it soon on it's own thread

Oh ... !!! "I can see clear now the rain is gone"
José Manuel Bonillla thank you very much for your clarification. Blessed mother language.
I understand everything perfectly and I'll try this way. I will keep informed you.
Permies, thank you very much to all for their attempts I see the light.

I have other questions now that you have shown me the way.




Among 30 gal drum and fire bricks raiser there are only air . I think the air is the best thermal insulator and cheapest. Can I use it as a final insulating of riser?

Can i do the same to isolate the burn tunnel and feed tunnel ? The idea is cover it whith masonry separate, leaving an air chamber among fire briks and masonry covered. If so, what would be enough air separation?

I hope my bad english will be understandable.

Best regards from Spain.

I have good news. I have made the changes indicated and everything seems fine. I only had time for a little test run, I have to try intensive use. I have to get the tubes to final installation and final test.
Thanks again for your help.

I need someone to answer questions from my last post. Please

Hello again.
First spanish, then english writing:

Vamos allá con una respuesta bilingüe
El aire aisla.. si está "encapsulado" entre otros materiales. Si tienes un gran volumen de aire en contacto con y dentro de la estufa este se irá calentando poco a poco hasta que deje de resultar eficaz como aislamiento. Si lo que haces es usar partículas de aire entre algún material ignífugo entonces no podrá pasar el calor de burbuja a burbuja, por decirlo de algún modo (explicación científica todo-a-100) y conseguirás el efecto deseado.
Puedes rellenar el espacio entre los dos bidones con arlita (el nombre que se le da en España a la perlita) "mojada" en barbotina (clay slip, pasta ligera de arcilla). La arlita es muy barata, unos 5€ el saco, y con uno o dos tendrás suficiente. La mezcla de arcilla y perlita para los "risers" de metal es más complicada de hacer porque es importante conseguir una proporción adecuada como para que una vez "evaporado" el metal del riser se mantenga en pié, pero en tu caso no tendrás ese problema así que será sencillísimo, y económico. Yo la mía la he aislado con manta cerámica, que me costó unos 35€

Por otro lado: cuidado con los morteros que utilizas en el interior de la estufa: a no ser que utilices los refractarios adecuados ser irán desintegrando con el calor, y se te puede desmoronar todo. El barro, económico, es la mejor opción. Lo digo porque ví en tus fotos algún mortero blanquecino que no sé lo que será... ten cuidado!

Me alegro de que vaya funcionando tu dragona! Ya nos irás contando.


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English now ((excuse me, please, not enough time to look for the dictionary now :p )

You wont't be able to make the air isolate the heat unless it is "confined" like bubbles inside some refractary material. If you have big volumes of air next to and inside the stove, this air will get hot and will transfer heat to the outside. You can make air work for you trapping it between some refractary material, as cheap perlite is. Clay slip with perlite is somehow difficult to mix in a right way for steel risers isolation, as you want them to stand upright as time, heat and oxidation make the metal disappear, but in your case you don't have to worry about that. So it will be a very easy and cheap way to isolate your riser and burn chamber.

I'd liket to advise you against the use of non refractary mortars on your stove! I could see some whitiss mortar used on your RMH test and I wouldn't like you to have problems with it as soon as heat makes his job! Cob is easy, cheap and GREAT for that things!

By the way: happy to read your RMH test is working so far! Let us know



Saludos
Greetings