Metal barrels are as rare as hens' teeth around here and flue pipe is prohibitively expensive too, so I pretty much need to avoid metal but I would really like to make an rmh.
I know a rocket stove is doable without metal, but a lot of heat is wasted, which I would like to 'capture' in a cob bench/sleeping platform. I am concerned that without the rapid loss of heat provided by a large exposed metal surface, there will not be sufficient force in the draught to force the exhaust through any significant lenght of horizontal flue, especially once the downward section has warmed up.
The only examples I have been able to find of anything without metal are just stoves, and only one of them a proper rocket even. The best of them is Glenn Herbert's, and that exhausts into a vertical flue, after only a tiny downward section.
Being unable to find anything like what I am hoping will work, makes me very wary of the massive amount of work involved in making a cob bench in the first place. . .
If anyone has made one, or has seen one that works or has a link to one, I would love to hear about it.
Hi Marion; Your flue/mass is easy, Brick tunnel of the proper size is easily built, or brick bells also work very well. As far as a barrel. Steel pipe can be used but it must have a top welded on. Used culvert would work. Even sheet metal (if you can weld it) would work.
Have you checked at any mechanic shops for a fluid barrel? School bus maintenance shops , even farmers end up with a barrel or two around.
As a last resort I would use all brick , it could heat up and stall but, that would be more likely with a flue pipe rather than if you use a brick bell arrangement.
Keep looking about and talk to people about what your trying to build. There may be just what you need sitting unused in somebody's barn waiting for you.
For all your Rocket Mass heater parts.
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You'd still need a bit of metal for the door, but there's none in the stove itself, and the bench is different type too, with no flue pipe.
Thanks for posting, but actually yes. It's not just having a door that put me off it though. Among other things more personal to me, I don't see how he can call it a rocket stove when it doesn't have a riser, and in the video he actually titles it a masonry heater . . .
Looking on the positive side though, it does seem to be exhausting satisfactorily through a bench even without a riser!!
Posting on here seems to do wonders for my search results, at least, for a little while. . . I've actually found a couple of diagrams and pictures of almost exactly what I am thinking of making, and afaict they work alright!
Hi Thomas, to cut a long story short, between my finances and ministry of sadness wranglings, for metal, I am limited to what I have had lying around for years, and that's not much!
I do keep my eyes and ears open for anyone who might be interested in these sort of things, but due to the normal (i.e. not like me ;P ) demographic of the area I live in, the closest I have found was over an hour away, and they had to remove it or be unable to insure a very expensive (and wooden) building . . .
My steel feed insert could be replaced with a firebrick feed easier and cheaper... I wanted to try it for the p-channel supply and air preheating; it works very well, but is not essential to operation.
An access panel to inspect the riser is a really good thing, but could be done much more simply than mine if you are not concerned with "living room" esthetics.