RMH does size matter, haha, beer keg or an oil drum

Hi i am constructing a small RS heater for my tiny home an old circus wagon. I have the option to cover the heat riser with a stainless steel beer keg, does anyone know if the diameter of the keg as apposed to the normal oil drum ie 33cm as apposed to 58cm would effect the performance. Any help before i cut the keg open, would be wunderbar.

Anthony Felton : There is some interesting physics Here. Hot Exhaust Gases rise in the Heat Riser, and tumble and mix in a Doughnut or Toroid shape.

There they radiate off 40 -ish % of their Heat Energy out through the surface of the Barrel (Heat Exchanger). The comparatively Cooler gases now Denser
and Heavier Sink vertically down to the manifold area where they turn 90º and flow horizontally 30 '+ (6 '' system)

A certain amount of heat must be radiated off of both Barrel(s) for the push-me pull-you effect to create this horizontal flow. If You have two Identical
Rocket Mass Heaters RMHs, with Barrels of different sizes but made from Identical Metals, The Smaller Barrel with a Smaller Surface area to Mass Must
Radiate the same minimum amount of heat as the Larger Barrel With more Surface Area !

In order for this to happen the smaller barrel has to radiate that Heat Energy at a higher temperature !

Practically, this means more of the heat radiated off of the Smaller barrel is radiated off of the that barrels sides instead of the top . The larger barrel will
be Cooler, and easier to snuggle next too, and protecting your exposures will be easier !

This is exactly why when your 3 year old is tired and wants up in your lap they are such a great cuddle! With their smaller Surface Area to Mass Ratio
they must maintain their 98.6º ƒ by radiating of their excess heat energy at a higher Surface (Skin ) Temperature !

Your Two barrels should be fairly close in their ability to be Both a heat sink and a radiator ( I Think!) Wall thickness; the thinner metal will radiate better
and cool down faster! - This is not a problem as the other 60-ish% of your Heat Energy is slowly being radiated off of the Surface of your Thermal Mass
Bench !

Ether barrel should last for years !

What is the white stuff under your J-Tube ? For the Good of the craft ! Big AL

Hi big Al, thanks for the response. From what i gather you think ether size barrel will work, be it at a price, due to limited width space in my wagon i will try out the beer keg as its 40 rather than 60 cm in diameter. As for the white thing under my mock-up this is a slab of very light quartz pressed insulation stuff my oven builder friend gave me, so far it seems to be very effective at keeping the wood cool under the J-tube. I can find out what it is exactly if you would like to know.
Keep you posted on my progress. Antz

Antz : O.K., A favorite quote of mine comes from the "Old Days'' of Stock Car Racing ! ''Run what you Brung !'' There are several right ways to do this !

( And Many more wrong ways ! ) A warning watch out for the incredible Boat load of stinking, steaming Crap posing as Functional Rocket Mass Heaters RMHs,
in U-Tube Videos ! Some can literally be called '' Flaming Units of Death "!

Experiment as freely as you want, after a very quite period of several years, reliable and affordable testing equipment is moving us rapidly forward, with
the experience you will get from This Build anything is possible in your future, We all would like to see your future plans and builds !

YES ! Please see it you can find out from your friend when and where this insulation is coming from and post a link !

Speaking about which Here is a link to help you post Your location ( who knows you may have a Fellow member who is a near neighbor with RMH and Cob
experience )

Link below !


https://permies.com/t/43625/introductions/Universal

Think like Fire ! Flow like a Gas ! Don't be the Marshmallow ! Big AL

No matter how good the insulating slab is, it will let some heat through, and unless you provide an airspace between it and the wood, eventually the heat in the wood will build up high enough to start burning. A free airspace that allows heated air to circulate away from the wood can be effective at keeping your base cool, combined with enough of the right insulation.

Building codes generally require at least one inch of free airspace behind a metal heat shield for any combustible wall or ceiling within several feet of a woodstove, and your barrel will need the same clearances and protection.

Hi Glenn, thank you for your suggestion the quartz insulation is so fragile that making an air bridge is very tricky, as it has a tendency to crack, hence i am currently conducting extensive tests with the current setup to gauge its effectiveness the previous concept had a metal frame involved and this proved far to heat conductive. i am so pleased to have a few heads out there who see.
respect Antz

If it's 33cm inside, it would be impossible. Ans the bricks are about 22cm, and the diagonal is 31 cm. So you would have nowhere near room enough for insulation and barrel gap, let alone barrel gap!

Max : Good Catch, metric measurements is something I am liable to be lazy about -

Antz : If I do the link right you can see a series of Video clips showing an gap underneath an RMH

Link below

https://www.youtube.com/watch?v=30rPCRB5e-s&list=PL0bZy202ImXP7NpLUJMtKJOjpjPPv59b-

This is available for purchase - but for purposes of discussion of air gaps it shows what you need to know !

For the Craft ! A. L.

The horizontal burning chamber looks too long to me. I'd suggest double checking your geometry.

Hi all, thanks for the input, the burn tunnel has been shortened and works, the smaller this thing is the better for my situation. I will also lift the quartz slab (sorry still waiting to find out the specs.), with 4x2 plywood strips. As for the bell i going with the old school 200l drum, but a 50mm would or feels like it would be optimal. I will post an update on the reorganized design.
Ta ta for now Antz

Antony Felton wrote:Hi all, thanks for the input, the burn tunnel has been shortened and works, the smaller this thing is the better for my situation. I will also lift the quartz slab (sorry still waiting to find out the specs.), with 4x2 plywood strips. As for the bell i going with the old school 200l drum, but a 50mm would or feels like it would be optimal. I will post an update on the reorganized design.
Ta ta for now Antz

If you are trying to lift the quartz to provide air flow (a very good idea in my opinion) I would consider using square steel tubing instead of a wood product (especially one which is impressed with chemicals you may not like off gassing into your living space). I've seen test lab builds online that have done this to protect their floors during test runs. I suspect it would work very well in your case too; better and safer than a flammable product in my opinion.

I would get a minimum of 1" square tubing. That should provide adequate air flow. More space = more peace of mind, perhaps, but costs increase too. I don't think anything more than 2-inch square tubing would be needed. On concrete I'd go with 1" and sleep well; on a wooden floor, trailer, etc, I may sleep better with the 2" air gap. Just my opinion.

Once again on the path to perfection. Well the white plate under my stove is something called CaSL short for Calcium Silicate
http://www.globalpiyasa.com/en/urun/kalsiyum-silikat-ca-si-plakalar-akm-metalurji-sanayi-temsilcilik-dis-tic-ltd-sti/36357
or https://en.wikipedia.org/wiki/Calcium_silicate
I hope that helps. America does not seem to use it( according to wikiped), but my Ground oven builder friend here in Germany seems to like the stuff
As for the lifting of the CaSl plate i may use strips of fermacell (another german product) The metal bars may act as condensation magnet and create cold bridges within the wagon ( better known as Bauwagen) no direct English translation.
Here is the latest plan idea, please feel free to comment.
I feel a little stupid building this thing during a heat wave 38C today.
Toodle pip Antz

I have been trying to figure out this website forever. I just want to ask a question can you use a beer keg on my rocket mass heater for the barrel.

Hi Graham;  Welcome to Permies.

A beer keg is a little on the small side. But depending on sizing and placement , you might make one work.

Let me tell you how to post on our forum. It's relatively easy , I think.

First pick a forum. Go to it. Here you picked the rocket stove forum.  I would suggest possibly the rocket mass heater forum.  
Next look for a  small box on the top right that says "New Topic"
This takes you to the proper place to start a new post. Such as "Beer keg as barrel ?"
Tell us what you are wondering about, or about your build.
If you wish to include pictures. You will see a small box below the message space that says "Attachments "
clicking on it , changes the page. You will see a small box in the center that says upload a file.
clicking on it will take you to your photos.  Click your picture and tell it to open.   (there are sizes that are to big and load very slowly)  
You can title your picture before submitting it for posting.

Hope that helps. If not , we will keep trying until you are a regular poster here at Permies.