Is a 2cm thick barrel ok ?

Hi, I think it's my first post but I've been reading a lot on permies for several years now. A big Thank You to the community !

I'm planning the construction of a RMH. I've bought the book "RMH builder's guide" by ernie and erica wisner and I would like to build a heater like the ones in the book.

One of the main issue is that I find it difficult to source the barrel. I live in France and it seems that this kind of barrel is not common here, the closest I can find is motor oil barrels that are way too thin (<1mm).

I recently found a big tube that is 52cm wide (ID) and 2cm thick, and I think it might be good for the RMH, but I'm a bit worried that the extra thickness (in the book it is said that it must be > 12 gauge, which is 2.05mm, so my tube is 10 times thicker) may be a problem.
The first problem I see so far is that it will take more time to heat and to distribute heat quickly via radiation. An other problem might be the dilatation/retractation of the metal.



Do you think I can use this tube for the RMH ? Are the problems above something to be worried about ?

Thanks!

Hi Tristan;   Big Welcome to Permies!   And A Big Welcome to the wonderful world of rocket science!

I think that your piece of pipe is rather thick.  
As you thought, it would take time to heat up.
The other possible problem, if you are planning on a piped exhaust thru a mass, is stalling the heat flow.

On a much better note.   The motor oil barrels you have are exactly what we use here. There is no, too thin. The heat dissipates fast. The most you would see is a glowing orange circle directly above the riser.
It would be best if you could locate one with a removable clamped lid.  However any 55 gallon (200 liter) size barrel will work.

I would like to tell you about another option.    All brick bells as a stratification chamber rather than a piped mass. And a batch box style rocket rather than a J tube rocket.
Here is Peter Bergs website  explaining all about batch box's.    http://batchrocket.eu/en/
They do require some metal fabrication, but its not to difficult.

Another option would be to build a J tube  and plumb it into a stratification bell.

As you can tell there are numerous options.

Here is another website from master builder Matt Walker.
Matt has designed super efficient riserless stoves and he sells the complete plans with full personal support from him.
Here is his website http://walkerstoves.com/index.html

As a side note. Each Wednesday at 11 am pacific time, Matt hosts a live chat with folks from around the world. You can ask him questions and receive his answer live!
Here is the chat site information.   https://www.youtube.com/user/broaudio.   All his previous chats are also available at any time.

We have a happy crew of rocket scientist eagerly awaiting your questions!  
We will leave the light on, come back anytime and ask questions!  

If the motor oil "drum" is around 55 US gallons, it will probably be ok. If you are concerned it is too thin, leave a healthy top gap (4-6 inches) and it will not get so hot.

Thanks for the quick and detailed feedback !

I will not go forward with this pipe then.

Ok for the motor oil barrels, in the book it is said that the barrel must be at least 12-gauge thick, that is why I thought it was not suitable. I plan on doing a "test rmh" before building one in my house so I think I will try with this kind of barrel and see by myself.

Thomas, what are the pros/cons of an "all brick" bell ? Walker's stoves seem nice (I guess you are referring to this design http://walkerstoves.com/batch-rocket-mass-heater-plans.html) but also a lot more expensive than the wisners which only requires a few bricks for the jtube + riser chimney (I've made a quotation for 100 refactory bricks, 250€. for the 300 bricks of the walkers that would be 750€!). Also, what are the advantage of a batch rmh ? All designs of batch rmh I've seen so far where made to be built in a garage for boiling water that is then circulating through the house central heating system. The walker's one is the first I see with a bench and that seems to be designed for a living room.

Hi Tristan;
Experimenting outdoors is an excellent way to learn about rocket stoves.  You will be happy with the motor oil barrel.
As far as bells go. I should start by saying that a "bell" does not have to be made from brick.  It can be all steel if that is what you have available.  Those folks that use a metal bell generally use readily available red clay bricks , either stacked outside around the metal bell or inside the bell. Heavy stones can be used in place of brick.
A note about bricks.  There are "firebricks" and then there are regular clay bricks.   Fire brick are only needed  where the temperature is over 300F or 148 C . Red clay brick is usually available used /free or very cheap. Firebrick is not very cheap Here in the US new firebrick is $1-2 each.
The nice thing about using a bell over a piped mass is size. A bell is tall and can be made to fit in odd shaped areas, a piped mass is low and long. A bell virtually has no ash buildup issues. A piped mass must be cleaned at least once every season.  
Difference is a long low mass you can sit / sleep on.   A bell you would just enjoy the warmth.

Batch rocket stoves are the newest innovation in rocket stoves. They burn hotter and last longer than the traditional J tube.
They use larger wood, the wood lays horizontal.  There is a door, so no open flames  nor any chance of "smoke back" a possibility with a J tube design.
The fire burns longer with no attention on your part.  A j tube requires attention at least every 30-45 minutes. A batch last's well over an hour and the coals might last 1.5 or more.
Spend some more time on Peter Bergs batchrocket site.  You will see many examples of his builds around the world.
I will mention that I had two J tube rockets at my home.  One has already been changed to a batch style  and I an collecting materials to change over the other J tube later this summer (i Hope).

Tristan,

https://www.leboncoin.fr/bricolage/1784393383.htm/

https://www.leboncoin.fr/bricolage/1799516219.htm/

For the thick old type.

But what you realy want is a barrel with top lid. So you can open the heater for inspection.

https://www.leboncoin.fr/bricolage/1815402406.htm/

https://www.leboncoin.fr/materiel_agricole/1769284677.htm/

That's just a quick search on leboncoin.  If you want the normal barrels, just go to your nearest point S or whatever garage they'll give you one.

Myself, i've taken advantage of what we can find in france, and i don't use barrels anymore, but home heating fuel tanks. They are square. Which is useful when you want to stick it against à stone or brick wall. The pics are further down. https://permies.com/t/44806/Cobbling-workshop-heater-cooktop-oven

Hope this helps.

Thanks again for your support and for the France advices :). I was able to find thick barrels on leboncoin but they are not a lot and often far away. I scavenged old water heater with round and rather thick round reservoir inside but they are too small for a RMH project, I'll keep looking !

For now on I think I will experiment with a motor oil barrel, one thing that bother me is that they are really dirty and covered with paint. In the past I made a small rocket stove (barnabé chaillot's onehttps://www.youtube.com/watch?v=R6pm-TD0P84) with a recycled gaz bottle and I burned the paint and gaz residues but it's not really eco-friendly... do you have advices on how to clean the barrel without burning the paint/remaining oil without burning and without a lot of work ?

I'm also considering building a batch stove after thomas posts... Seems like they are easier to use, safer and longer lasting... Lots of thinking, reading and internet searchs ahead !

Tristan, without burning, or lots of work, not a chance.

There are options.

A "maturateur à miel" is one, often in stainless steel.  https://www.leboncoin.fr/bricolage/1182982354.htm/  Hard to find.

Stainless barrels. https://www.leboncoin.fr/materiel_agricole/1812504777.htm/   https://www.leboncoin.fr/bricolage/1797677122.htm/  

But there is a few and far between.

There are other options;

"baignoires" (bathtubs) and "cuves à fuel" (home heating fuel tanks) Bathtubs, for a "half barrel system" mostly. Home heating fuel tanks, for the barrel.

Caustic soda and hot water pressure washer are a must.

Otherwise, you do a "pocket rocket" in your big barrel, and surround it with rockwool, to burn your paint. After, you clean with a wire wheel.

You do like this without the barrel inside, and wrap it with rockwool.