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Fishy's Rocket Mass Heater Build - Part 1


Should have part 2 up in a few weeks. THANK YOU again, Twelve-Oh-One. This vid's for you!

Anybody want to use a free trial of the editing site I used? If you use this link to get your free trial, I get more free editing sessions, and it is much more versatile than the youtube editor. Use this link to get one free HD video for yourself, and one for me! Thanks!


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For sharing this link!

*edit: this was directed to Myk's comment below with a link to dragon heaters.

Best heaters in the world

I remember way back reading about the Russian Fireplace in the Mother Earth News Magazine. Being as poor as many of those people are up there in Siberia the necessity of making the most efficient design for a fireplace was a matter of survival. It's a complex and compact fireplace but it supposedly wrings out every last bit of heat from your fire before exhausting out into the air. Look it up in the Mother Earth archives, it's pretty cool.

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deacon's picture

I built my own

Rocket mass heater.8 inch pipe insulated inside a 10 inch pipe.
Worked rather well,but burnt too fast,by this, I mean,it would burn the wood to fast.No smoke on initial startup.Heated the house fast.Then I added another bend which measured about 5 ft.Now it smokes in the house,hard to keep lit.
I was looking for the instructions I had before,can't find it on this NEW computer (refurbished my old one,after a melt down)...anyways,what I cannot find is how close to the top of the barrel does the inside insulated pipe need to be to work efficiently? And not smoke,but still burn,and stay lit?

If we deny truth before your very eyes,then the rest of what we have to say,is of little consequence

About 6 inches

My husband has spent about 20 minutes trying to explain the math to me, and I am giving you the "final answer." If you want more info, please contact me and I will put you in direct touch with the brains of the operation.

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deacon's picture

I guess

I should have waited,mine,right now is about 3 inches from the inside top of the barrel,seems to work better than it did
One commenter below stated about an inch and a half,this is what I read before building mine.That was a bit close,and didn't work well after changing from 6 inch pipe to 8 inch.
Not sure of your meaning about contacting you,I thought I did done that with these comments. :)
You could drop me an email through this site,that is,if you want to have yours in return.
Thank you so much for sharing your knowledge.

If we deny truth before your very eyes,then the rest of what we have to say,is of little consequence

Let me try this

Message sent, but I will try to summarize here for anyone else looking for the info and to try to get my own brain around it better.
First, lets name some parts:
You have the "cold flue" where the heat enters the mass. You need the area of this. It should be just a little bigger than your hot flue, same size at the minimum.
You have a "hot flue" where the firebox area enters the burn chamber is. You need the area of this. This should be smaller than the cold flue but larger than your firebox feed opening.
You have an "firebox feed opening" is your smallest opening.
You have an "adjusted barrel surface area" which would be the surface area of the barrel top minus the area of your stovepipe below (outer ring of your double wall.) This number needs to be at least 1.5 to 2 times as large as the last number to calculate, below:
The last number you will need is an imaginary cylinder that has the diameter of your stovepipe (outer ring, so 8 inches for you) and is as tall as the distance between your stovepipe and the lid of your barrel. This is the height you are looking for, where Mark said 6 inches. Use this calculator for lateral surface area:

Please note the calculator uses radius, not diameter.
I hope that helps.

Love or fear? Choose again with every breath.

deacon's picture


More details might help all.
I built mine using a 55 gal drum with removable lid.I took the rubber gasket out of the lid.the stack (chimney inside the barrel) is attached to the lid,which sits upside down.This is 8 inches,as is the inlet tube for the wood
the outlet side is 6 inches(this is pipe that runs through the house,then back to the chimney to outside
I made it this way not only for a complete seal,but to be portable as well.
I started out having 6 inch pipe for the inlet and outlet as well,but it sucks so well when hot,it would suck the flames out,this is why the inlet is 8,and the outlet is 6.
I had to make my own pipe flanges to mount the pipe to,as they are not found around these parts,but can be bought in barrel kits for about $45,and that is a bit steep for just one part from that box.
Next I ran the pipe in an L pattern to follow 2 walls,the pipe sets on cement blocks and is them back filled with bricks to retain the most heat,then the box was put around it all,Mine so far is not done,as cushions
are hard to find,other than the ones for lawn chairs (might to have to make my own as well using 4/6 inch foam,then sewing my own fabric for the forms)
It does work better after removing some of the chimney from inside the barrel,but I still see and smell smoke outside,this might for 2 reasons,1 being the 6 inch outlet,and the 2nd,might be because the chimney is still to close to the top of the barrel.
MY next one will be with a 35 gal barrel like I did with the 55 gal drum,but with a 55 gal drum around the 35 gal barrel,the 55 gal drum will have holes drilled for air flow,and a fan installed to blow extra heat around the house,Maybe pull air from upstairs through the house for recirculation purposes
I built mine for around $200 bucks...Because the first attempt didn't pan out,but the whole thing as it sits now,can be built for half that...I got off cheap as we are tearing down 100 plus year old house next to us,I kept the piping which is now being used to transfer heat inside the L shaped box...Off topic,we are also keeping all usable wood,and am going to build another house with that wood,and the stove will be used in that one,am thinking about having the inlet outside,and the barrel inside,this way I am heating outside air,and not drawing air from outside in ( I feel the cold air being pulled inside)
Thank you and yours for the time and the info,I appreciate it very much
P.S.,received your email,will send you one with my contact info shortly

If we deny truth before your very eyes,then the rest of what we have to say,is of little consequence

DIY is fun, but this dragon breath pre-built looks like

the most efficient "burn" I've seen yet.


Their mobile, too! The 8" is a little on the heavy side for some (92lbs without barrel), but is very manageable with 2 people.

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deacon's picture


And thank you for that link.A bit out of my price range though.
Mine is built to be transportable,as I plan to move,it goes with me.
When I get the bugs worked out,it should work great.

If we deny truth before your very eyes,then the rest of what we have to say,is of little consequence

You bet, Deek!

Saved up $200 a month to get the "okay" from the misses.

She still countered with, "Why not just get a 1/2oz of Gold instead?"

I love that woman...

If you don't know your rights, you don't have any.

Jefferson's picture


Like to have one of those, and one of these too.

And about 50 yards of woodchips on the property. Not sure Santa can fit that on his sleigh...;)

Wow, Jefferson.

I have never seen one of these....expensive as hell, but looks very "sustainable."

Off to read some more about this thing...

If you don't know your rights, you don't have any.

Jefferson's picture


was a guy who came on here a while back who had designed a DIY model. He got panned because he was actually charging money for the plans he worked his tail off on. It looked like a pretty sweet setup. I wish I could remember what he called it. Wait, here it is..

My question is how much wood do you have to feed them in a 12/24 hour period?

A friend of mine is getting the tree trimming companies to drop their chips on some of his property. He's planning to use it for mulch but it'd be the perfect fuel for these gassifier generators. (i think)

You didn't know about gassification? What kind of prepper are you!??
*as CNN is informing me right now about the vulnerability of our grid from Chinese cyber attacks*

the ones I've seen

are 1 &1/2 inches from the top I believe. You could try permies.com too.

"Politics ought to be the part-time profession of every citizen who would protect the rights and privileges of free men."

Dwight D. Eisenhower

I love it,

Send me your email address and I'll send you shipping instructions to my house, after it is finished of course. Don't worry about the shipping costs, I'll pay you one day. Tell Mark how much I'll use it and appreciate it. Again, thanks Fishy.

cold winter hot spring :D

Cool vid, cool song. THANK YOU!!!

Part 2

Please, FIRE that baby up!!


Lets burn that fatty now!

Cyril's picture

BUMP for knowledge.

BUMP for knowledge.

"Cyril" pronounced "see real". I code stuff.


"To study and not think is a waste. To think and not study is dangerous." -- Confucius

Cyril's picture

Thank you for posting this!

Thank you for posting this!

"Cyril" pronounced "see real". I code stuff.


"To study and not think is a waste. To think and not study is dangerous." -- Confucius

Hey that looks familiar like

Hey that looks familiar like deja vu or something... ;)

End The Fat
70 pounds lost and counting! Get in shape for the revolution!

Get Prepared!

That guy laying the bricks...

He's a handsome fellow, is he not?

Love or fear? Choose again with every breath.

Video feedback

I'd like to learn more about this rocket mass heater and how it works. Any links?

Bit of feedback on the video itself, the editing is too heavy. I found that I developed a headache from the transitions between clips, because it darkens the scene too much for me to comfortably see the actual content, and when the white grid appeared my eyes had to readjust for brightness. It's kinda like being in a well-lit room, and then a fog of night falls, which turns to day in a second, and then clears away only to come back again. The effect is that I only saw half of the actual video content over the full video length.

The music might've been too loud, and some audio commentary could've made a good guide as to what you were actually doing.

Video editing should always come second to the content you want to show, and should never be the highlight. You need to think about your audience's experience of the video: they're here for the project, not the FX.

The build and raw video itself is good stuff. The video editting just needs some improvement. :)

I believe in the freedom to be what we choose to be.

RMH details


If you get serious, I can email you a pdf with specs, too.

Sorry about the editing, I am really no videographer at all. I wanted to show each step of the process, but often as not, I was covered in concrete or mud myself so I just took short clips. I wanted to put that song to it, and youtube only lets you pick from their music files so I had to learn a new editing program. The white grid lines are what drives me nuts, I do not even know why they are there. I am going to try to program suggested below for my next video, and I am going to try to get good at it. We want to produce a series of high quality educational videos, so it is definitely time to up my game.

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Cheering you on the way!

Good luck with your videos! Learning something new one step at a time...

I believe in the freedom to be what we choose to be.

I'm a big Renewable Energy fan

I'm a big Renewable Energy fan (mainly windmills and solar). But I hadn't encountered the "rocket" systems before. Thanks enormously for bringing it to my attention.

I did a bit of web searching and found a bunch of good stuff on how they work and how to build them. Beautiful.

- Similar combustion efficiency to a pellet stove, but far better heat capture.
- Natural draft instead of forced draft by electric fans.
- Manual feed instead of electric auger, but batch, requiring no more (indeed, even less) attention than setting a fireplace fire.
- Thermal mass heat storage so a single fire heats for a day or more.
- No power or control requirements beyond setting and starting a fire every day or three if the house is getting too cool.

One thing that really impressed me is the hack of getting a high draft from a couple feet of "indoor stack", rather than an external chimney, by running a counter-current coaxial heat exchanger with extra heat added by the afterburner combustion on the inner, upward-flowing gasses and heat extraction from the outer, downwind, side of the flow. Cute! A pure-fluidic/convection heat-engine to pump the air and deliver the partially cooled result back down to the level of the fire for horizontal exhaust after nearly all the remaining heat is extracted from the fully-combusted exhaust. Extreme temperature differences produce a strong draft with only a couple feet of rise.

And of course:
- Cooking surface on the top of the heat exchanger/engine.
- Practically free but for labor. (Made of mud, firebrick, maybe some flue pipe, and a 55 galon "oil drum" or similar.

I'll be very interested in:
- Ash cleanout.
- Smoke from initial startup and how to avoid it.
- Longevity and failure modes of that "oil-drum" outer heat-exchanger wall.

My eventual retirement home is currently heated by solar and propane, with a gas forced-air furnace for main, a milliwatt-stat/pilot-light propane stove for backup (in case of power outage), and south-facing solar windows (which are fine for daytime but we have too low thermal mass for store for night or overcast days). I'd been thinking of moving my pellet stove there and getting a pellet mill to fuel off the annual weed crop and home-generated electricity. But this system looks like a GREAT "after a hypothetical fall of civilization" alternative. B-)

= = = =
"Obama’s Economists: ‘Stimulus’ Has Cost $278,000 per Job."

That means: For each job "created or saved" about five were destroyed.

Here is a setup with easy ash cleanout


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You sound like my husband. I am not an idiot, except on things that I am an idiot... like understanding what part of the heater is doing what.
Our ash clean out is hard to see in the video. If you look at the part where just the firebrick is done, the opening on the left is does not have a full "floor." There is a gap, about 1 to 2 inches between the end brick and the last "floor" brick where ash can be pulled from the burn chamber onto the floor in front of the stove. Well, I'll put a pan there, but you get what I mean...
There is another clean out that will be on the flue end, at the first angle we will put a "T" in, and make a clean out of one part of the "T." To get the stove burning properly, you can cheat and stuff a little burning paper in that clean out to get things drafting faster. If you are concerned about smoke, some people put the stove outside and run the flue inside and build the mass over it, then run the end back outside.
I have seen some reports of drum and burn chamber pipe failure, some people build the whole thing out of brick, but that gets a lot more expensive unless you can salvage the brick.
Thanks for posting. That is why I do these silly videos - I KNOW there are people out there looking for the same answers we are. I share what I figure out, others share what they figure out, maybe somehow we will get this all figured out...

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Fishy you are shining Love here


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Looking forward to trying this myself in the near future.

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