Hybrid rocket stove for tiny trailer house

I'm currently building a tiny house on wheels around 8'x18'. (With the "cathedral" ceiling, I figure the interior is around 1200 cubic feet.) After evaluating many woodstoves (such as the $3500 Kimberly Stove, the smaller stoves from Morsø, and the Hobbit Stove from Salamander Stoves) I am now exploring the (hopefully cheaper) option of building my own. (I move in April 15, but won't install a permanent heater until fall.)

Obviously being on a trailer introduces weight limitations, so a conventional RMH is out of the question. However, I think it's possible to make some sort of hybrid, usable also as a cook surface.

I'm imagining a steel 5 gallon bucket as the drum, with J-channel and internal riser. The top of the riser is very close to the top of the drum, giving a usable cooking surface. The drum is surrounded on the sides by a mesh cage creating a cavity (maybe 1-3 inches?), which is filled with rocks. The cooktop provides some "instant" heat, while the rocks give off gradual heat. (The rocks also decrease the chance of burning myself.) There is no lengthy exhaust pipe - it goes right to the chimney after traveling down the outer portion of the drum.

When not cooking, some additional thermal mass - a pot of water or some bricks - can be placed on the cooktop.

If necessary, the rocks could be removed prior to transporting the house, for an easier load on the axles.

The basic goals here are:
-Provide a cookstove
-Provide heat as efficiently as possible (the cleanest burn and the coolest exhaust) such that I can leave my house all day without it freezing over
-Avoid burning my (pretty flammable) house down
-Avoid burning myself (or worse, my guests)

Thoughts?

(One other idea: Perhaps I could integrate a non-mass bell - another 5 gallon drum perhaps - to heat more air before the exhaust leaves the house? Obviously heating air is less efficient than heating mass, but it's way better than losing the heat to exhaust.)

Hey Garrison, I'm in the beginning phase of a tiny trailer house and am looking at exactly the same options as yourself. Currently leaning towards the Hobbit stove but would love a more permaculture solution if there was one. Tiny trailer houses, by their portable, lightweight "massless" and low-R natures, don't seem to hold heat well.

What did the gypsies with the vardos do for heat?

Looking forward to answers to the questions you posed...!

Hi Garrison. I'd love to hear where this exploration goes. I'm in the beginning of building my tiny house, but was thinking of a rocket stove. Where are you located? Maybe I can come and help you.... warmly, elena

Welcome to permies! Three new folks at once!
Garrison, Have you tried building a mock up ,outside the home , to see if the idea works? If it does I have a trailer I might have to try it in.

Water would be a good storage medium if you can figure out a way/place to store it and also make sure you don't end up with steam.

Garrison B. : I don't think that you will have enough room under your 5 gal pail to accept a tall enough Heat Riser without setting your 5 gallon pail
on a couple of additional levels of brick or cob, increasing the weight penalty your trailer will have to take ! Remember that your Heat Riser needs
to be three times as long as the feed tube is deep, and twice as long as your burn tunnel, and you need a tall well insulated Heat Riser to get a good
clean efficient burn.

The Rocket Stove gets its ability to drive the exhaust gases horizontally from the temperature difference between the gases at the top of the Heat
Riser and the cooler temps at the bottom of your barrel. Even though you are planning on not using any thermal mass after your pail or Drum it is
very likely that when the rocks (that you a placing in direct contact with your barrel?) come close to equalizing temperatures with the Barrel AND
the Heat Riser, the Rocket effect will stop working. Please let us know if your Stove continues to function under these conditions, especially with the
exhaust lower than the opening of the feed tube (or you could possibly bring your exhaust horizontally off of the side of the bottom of your drum!)

Please let us know how this system works for you, I too have a trailer that could be a moble home if an efficient Rocket Stove could be made to work
in this way! Be Safe, keep Warm, PYROmagically -Big Al

Interesting thread,I have just joined this great forum. I have a ton of research to do on this concept . I have a very tiny cabin I will need to heat,it can get 40 below here so I have to choose wisely.

Dale Alan : Welcome to Permies, and the rocket stove forum/threads you will find a lot of good information here and at the Woodstoves and Cob Forums Threads !

So that we are reading out of the same book, please go to 'rocket stoves.com' and download your PDF copy of Ianto Evans' great book 'Rocket Mass Heaters'
$15.oo U.S., there is no other book in any language that contains as much Rocket Stove information in one place (-and I don't make a nickel)

Are you comfortable sharing your approximate location? It would be nice to know what parts of your cabin you have planed to heat, and any adjacent rooms or voids .

A simple sketch showing Number of windows and where south is located, and number of square feet will get us started !

For the good of the Craft! Be Safe, Keep Warm, PYROmagicly - Big AL

You could heat thermatic oil and use it as your heated mass and/or circulate it through a radiator. A lot of electric space heaters actually heat thermatic oil that is inside the unit. All you would be doing is skipping the electric heating. Could run the oil through a coil in the stove, I guess. Or, heat a container of oil on the cook top section and circulate the oil out of and back into the container.

Just an option.

I agree with Allen, putting thermal mass around the barrel will impede the rocket effect of the burner. If you're looking for an effective weight/thermal mass you should look at "Phase changing" thermal masses. There is a wax that has been impregnated with other minerals that melts at a much higher temperature than regular wax.

Here's the sciency bit (the parts I live for!): The temperature of the wax will continue to rise until it begins to melt. From this point on, the temperature of the wax WILL NOT INCREASE any further until the entirety of the mass has reached a liquid state. When all of it is melted, then the temperature will continue to rise. This is also true in the reverse (thus the beauty of the material). As the wax cools, it will remain a steady temperature until all of the wax solidifies, at which point it will actually drop in temperature.

This really gives you a good, steady heat, and I don't think it would take too terribly much to heat your small building. Just a thought, there are tons of options out there

Hello Hello! I am new to permies! I love the forum, youtube videos and podcasts. I am also looking into a smaller version of the Rocket Mass Stove for a tiny trailer house. I am in the need for additional room in my house for a home office. Since I want to eventually live off grid. I was thinking about building a tiny trailer house for my home office and future use!

Any ideas, links or points in the right direction would be great!

Other links I found so far...

https://permies.com/t/22491/rocket-stoves/Rocket-stoves-essential-oil-stills
https://permies.com/t/7259/wood-burning-stoves/Small-Rocket-Mass-Air-Heater
https://permies.com/t/6764/homestead/Rocket-stove-trailer
http://www.waldeneffect.org/blog/__34__Why_don__39__t_you_heat_with_a_rocket_stove__63____34__/
http://www.hearth.com/talk/threads/rocket-stove-mini-mass-heater.109323/

There is a new option I just found: http://www.rocketstove1234.com/hunter_indoor_woodgas_stove.htm#sthash.FnZXvzMo.dpbs

Use an old cast iron pot as the lid (like the rings in an old wood cookstove) when you aren't cooking. The idea is for it to be a summer option for a wood cookstove in a house/cabin (vs. a normal wood cookstove), but it seems perfect for a tiny house.

R Scott wrote:There is a new option I just found: http://www.rocketstove1234.com/hunter_indoor_woodgas_stove.htm#sthash.FnZXvzMo.dpbs

Use an old cast iron pot as the lid (like the rings in an old wood cookstove) when you aren't cooking. The idea is for it to be a summer option for a wood cookstove in a house/cabin (vs. a normal wood cookstove), but it seems perfect for a tiny house.

Another new member here. I have the Silverfire cook stove that you are referring too, and it is a great cook stove. Because the stove itself is insulated it gives off very little heat and therefore would not be ideal for warming a small cabin. While still expensive, another option, the simplefire heater.

http://www.simple-fire.com/html/videos.html

Has anyone been using the Hunter Wood-gas stove for awhile? I'm wondering if it holds up over time. Is it as efficient as a well built and designed rocket stove? Thank you

Hi, I made this, it is a off grid hybrid (pellet and/or 16x 2.5 inch log) stove. In the testing phase I kept my uninsulated contractor trailer warm from -32C (-25F ) to +32C  (90f)  with pellets only. I have managed now to run it cooler so I can use it on cold summer nights ( I'm in Quebec Canada) from 10c (50F)outside to make a comfy 20-21 (68-70F) inside for 6 to 12 hours (varies with exterior temperature) with no care... I empty ashes every 24-48hours and put pellets in once twice a day. This is version 2, I'm now at version 4 and improving esthetics phase. I also use it to cook and boil water. It is 12x16x12 inches overall and uses a 4 in chimney.  I love self sufficiency ! Inventing and making inventions safe and easy to use! I am considering selling plans or patenting the burn chamber and manufacturing it. Looking for partnership... direct link

Daniel,the video is not so helpful to me. Would you post several photos, from several angles, with dimensions and materials used or cost to build: hard to tell if it would suit the needs of many (making it worthwhile to sell plans) from what I can see in the video.

This may or may not help, but I thought this tutorial on how to make a door for your rocket oven was really simple and helped me feel more confident about going forward with my project.  https://permies.com/s/oven-door