My portable Rocket Mass Heater

[matt walker]

Yeah, there's a bunch of talk over on the Rocket Stove board of trying to hook up either an auger feed or a slide type feed. I'm not sure anyone's got a working one yet.

http://donkey32.proboards.com/index.cgi

[Cliffystones]

Hello Matt,

I'm excited about finding your discussion group. I'm an avid do-it-yourselfer who lives in Colorado halfway between Denver and Co. Springs. I've been contemplating building a Rocket Mass Heater in my basement as a supplement to the other heat sources I have. After my central unit died on a single-digit weekend day , I have invested in some kerosene and propane heaters.

I love the idea of the "portable" unit. Most of the wood readily available to me is rather small (scrub oak mostly). I wanted to build a smaller stove for burning this and other scrap wood. And maybe compressed or rolled up scrap paper.

I know I have a lot of reading to do yet. But a couple of questions come to mind. Do you have any tips for where to find the smaller metal drums? The suppliers I have found just have 55 gallon ones. And while I've read several books and designs I've never seen a stove where someone has increased the height of the chimney/barrel. The designs are usually one-barrel-high. I wonder if anyone has tried a 2 or 1-1/2 high chimney? My thinking is that this would increase the draw.

When I get around to building mine I'll be sure to take pictures and keep you posted. Thanks again for sharing your designs and experience!

Cliff Shelby
Castle Rock, Colorado

[matt walker]

Hey, welcome Cliff! Glad you found us.

As for the small drums, they are commonly called Grease Drums and can be found at oil change places. The big chains like Jiffy Lube can be sorta stingy, but I've had good luck asking at places that service big rigs. They usually have a bunch of 'em laying around.

Funny about the 2 high barrel stack. I did exactly that in my shop last week while testing a prototype stove core. It's a great way to maximize getting heat into the room quickly. In mine, the heat riser was standard height, and the double barrels acted as a large bell to allow the gasses to transfer heat into the room as efficiently as possible.

Here's a link to a really cool, modular design that might give you some ideas.

http://donkey32.proboards.com/index.cgi ... &post=1682

http://donkey32.proboards.com/index.cgi ... thread=197

And here's a photo of Peterberg's version of the double barrel bell. Mine was similar.

[Cliffystones]

Matt,

Thanks for the info. Sometimes just finding out what something is called can be the trick! I'll have to call around and check Craigslist for those barrels.

Is the stock tank 2x2x4 feet? It looks like it. I hope so because there's a local guy who has 3 new ones he's asking $40 each for right now. I like the idea of using the stock tank, especially for my first attempt. I was going to go a step further and build the whole thing on a couple of large furniture dollies for true "portabilty".

You say there's 5-6 feet of pipe at the thermal mass side? It doesn't look big enough from the pictures, but I'm sure that's my perception. Does it travel in a "S" pattern? A little internal diagram would be greatly appreciated. My other thought was to use firebrick between the stock tank and the burn chamber to get the chamber as close to the tank as possible. And I'm debating whether to use a 6" diameter flue on something smaller. I thought a smaller diameter would lend itself to the burning of smaller fires with smaller pieces and less wood while still drafting well. If anyone else has tried this with say a 4" flue, sharing their experiences would be appreciated.

Thanks,
Cliff Shelby
Castle Rock, Colorado

[matt walker]

Yep Cliff, the stock tank is 2'x2'x4'. One thing about the tanks, they are galvanized, so if you build it such that it gets really hot you run the risk of gassing off the zinc, which is really bad. Google metal fume fever to get an idea, and do what you need to to avoid it. You can pre-burn the zinc off outside, or just insulate such that it will never reach the temps required to gas. I'm not exactly sure what temp that is, but you can find the info online.

You'll want to use 6" for the whole system, no smaller. Smaller than that and the boundary layer friction will slow down the system such that it will never work properly. The 5' of flue I have in the second half of the barrel is all adjustable elbows set up in a spiral. I have since disassembled that system, but I think I had 6 of them in there spiraling up and out.

I like the dolly idea, but be aware that right under the burn chamber can develop a lot of heat over time. Even through insulation. Make sure you leave that space bare metal or something. Don't set it right on wood.

Good luck Cliff, keep us posted.

[smallhagrid]

Hi Matt.
I went through all the postings in the heating/cooling area prior to posting and very much admire your stock tank idea !!!

Just so happens there is one in the pasture here that is leaky, and loads of rocks too.

Have you posted details of the burn tunnel you built into this one anyplace, please ??

If I used the tank from here I could easily cut a hole into it for the exhaust and it looks like yours used a 30 gallon barrel for the riser cover - is that correct ??

Thanks.

[matt walker]

I just did a basic brick burn chamber in that one. If I were to do that again, I would probably just cast a core directly into it. Follow my core casting video, but use the tank for the outer mold container. You would use a LOT of material, but it could be mostly found clay. I would just pack the fancy mix around the inner mold, then fill with local clay/sand/perlite, or something. You are getting into experiment territory, and will need to just get dirty to go much farther on that design. Be very careful with the stock tank indoors, it is galvanized, so you must ensure it never gets very hot or it will offgas. By "very hot" I'm talking well above 500°F, but I'd want to be dead sure it stayed well, well below that. Insulation is really important.

[Lollykoko]

I had totally forgotten about this thread!! Thanks for bringing it back to my attention, Small Hagrid and welcome to the forum!