Rocket Mass Heater Shippable Core

Dragon heaters has had something out for a while now, but every time I look it seems to have two or three things that fall short of what I am looking for. I have great hopes that their products will evolve into something that I wish to support.

Cindy Mathieu wrote:
Paul, you have never said what the two or three things that fall short are. We still have no idea to what you object about our shippable core.

paul wheaton wrote:A few years ago I went to Ernie and Erica with the idea of a shippable core. Ernie told me that the idea was not new. However, the one thing I pressed for did sound new: that the core would be casted and would include a manifold.

Many conversations and a lot of work from a lot of people and PRESTO! We are having a workshop in October of 2012 complete with Ernie's shippable core. It was more "sculpted" than "cast", but, hey, it was a prototype. We thought we could get the materials for under $100. Then came the shocker: more like $500. Urk! Work, work, work .... lots of other people involved .... work, work, work ....

I came up with a simple idea of the wood box style shippable core shortly before the October 2013 workshop and offered "build your own" at the event. In the five days before the event, a LOT of innovation happened and three different shippable cores were created. When people arrived, we showed what we had come up with and people were asked which they wanted to build and take home. Nobody wanted mine (wood box style) nor ernies (an improved version of the 2012 stuff - still very expensive). The big winner was Erica's cast core with a manifold:



In second place was Erica's cast core that did not include a manifold. Erica is clearly the big winner.

Unfortunately, that core went to the tipi outside and was subjected to freezing and thawing before it could be fully heated properly. So it developed cracks. But Erica's work led to lots of inspiration and then perspiration. Erica came back and worked with my brother Tim to come up with better molds, better mixes of castable stuff and something like a poor man's kiln to properly cook the core.





We have one core here now that has been fired about 40 times and seems to be holding up. Costs have been gut wrenchingly high ...

(I would like to take this moment to thank the people that have supported my kickstarters)

.... but we are working hard on being able to get a design completed that will be able to shipped to somebody's door (in the US) for a total of $500 or less.

Plus, several people who attended the workshops went home empty handed. Those people will get the prototypes that seem to keep working.

....

I want this thread to be the central place for all things involving a shippable core.

For all of the information being developed here, I plan on sharing it. We (me, Ernie and Erica) are still open to the idea of supporting somebody who takes these designs into production for a business. Ernie and Erica are powerfully focused on R&D and I have a powerful need to see this product exist (and no interest in being in this particular business).

I do know of one guy that I have spent a few hours on the phone with .... and he has been here .... and he has some amazing ideas in shippable cores - but I am sworn to secrecy. I really hope to someday see his product.

I think there is a lot to be said for this design, once it gets some manifold stuff added to it:



Matt Walker has created something that might have beaten us all to the punch:

I wonder how much it costs. How big it is. How do you connect it to the mass? It certainly has a wood feed, riser and manifold.

Dragon heaters has had something out for a while now, but every time I look it seems to have two or three things that fall short of what I am looking for. I have great hopes that their products will evolve into something that I wish to support.

I was unsure how to build the heat riser and then looked up Cement tubes, and found that basalite has a lovely 8" diam X 12 " flue liner made of clay. I bought that for $17.

Gaps between the boards, and what is holding the boards together.

To me, it isn't a core until it contains a manifold.

Jesse Biggs wrote:For some weeks now I've been working on a core with the intent that it might be shipped or moved at some point. I've run into lots of snags. After the last snag, I went on a youtube binge and stumbled upon a technique known as "slip casting". Currently there are 1/2 scale plaster molds in the works in my basement.

(youtube video on slip casting removed)

If this works out, I think it will fall into the realm of "freaky cheap".

Peter Berg wrote:
There's another consideration against one single casting in play here, namely cost. The hottest parts are also the parts that could recieve abrasion from the fuel or cleaning out actions. So material that is soft and insulative can't be used for feed, burn tunnel and the lower region of the heat riser. The level of heat resistance should be about 2400 F here, way more than the rest of the casting. When this complicated casting could be split in two or three separate parts, respecting the different temperature zones, that could bring the price down significantly.

Peter Berg wrote:Len Ovens,
As far as I can see, there's no fixed floor in that casting. The only option would be to have a burn-out core in the burn tunnel then. Better is to use a separate firebrick floor underneath the casting, much simpler to produce.

I find "you have never said" to be rather offensive when I have said. I even find it to have a rather accusatory tone. And then when I provide a link to where I have said, then a person could say "oops, sorry about that. I don't know how I missed that!"

As for "competition": I am perfectly comfortable supporting multiple shippable cores.

paul wheaton wrote:All castables have failed here. The one that lasted the longest was the one with lots of reinforcement in the goo. It was also the lightest. But it eventually crumbled too. It also cracked in a spot that seems like it would not ever get much warmer than room temp. This leads me to think that it might be dealing with high temps just fine - it's just that the material is not very strong. Although we are exploring some ideas that we might need to improve our kiln process.

But we are also thinking that a kiln process is time consuming and energy consuming. So, that drives the price up.

We are going to start limiting experiments to riser segments with the idea that we want the material to pass that test before trying a full core.

Cindy Mathieu wrote:

Multiple companies can't be supported in such an environment.

paul wheaton wrote:So the red area is greater than 50 square inches?

John Adamz wrote:I've read extensive discussions about the size of the manifold area here and on the donkey proboards (research by Peterburg), and the conclusion was that it needed to start at least 2x the CSA of the core. So for an 8" core it should be in excess of 100"sq. It also seems that by creating a venturi effect with the manifold the smoother (edges/corners) the transition from the gasses around the barrel/riser to the exhaust duct the better.
I think Jesse Biggs current system is an excellent example of that principle.