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Post by Donkey on Feb 22, 2015 1:32:23 GMT -8
martinpolley, Look carefully at the build pictures, you will see that the heat comes out of the riser, strikes a plug and flows in all directions through several horizontal channels to the outside edges of the dome at the bottom. There is a channel leading down from one side of the oven that takes exhaust (when the door is closed) through a lower hot water heater, then down again to the chimney. The chimney exit starts quite a ways below the oven but above the level of the fire. When I fire it, I only leave the door open for about 10 minuets tops. Just long enough for the firebox to come up to heat and go clean. Then, I close the door so that heat will be forced to go down from the oven chamber. The thought is that it will act like a bell, keeping the hottest gasses inside for longer. I made a "pizza stone" thing with local clay, mixed with wood-ash, sand and a little chopped straw. It didn't quite fire in there and making it just small enough to barely fit through the door in one piece makes it really too small to be a good baking floor. I plan to make a new one in quarters (or something) to fill the whole space.
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Post by Donkey on Feb 22, 2015 0:56:55 GMT -8
There is a little bit of the "not invented here" thing going on.. Ianto has been very resistant to some of the new additions to the J-tube as well, such as the tripwire and p-channel. He also doesn't feel comfortable writing about stuff that he doesn't personally know about. He doesn't experiment with stoves any more and it is quite likely that this is the last edition of the book that he will be a part of. His health lately has been a rather bumpy ride and I think he would rather spend his time with his first love: the garden. If there are to be other books about Rocket Stoves, someone else is going to have to write them. As to the problems with J-tubes, it's our job to find out why and educate people about it! In my opinion, the major problem with them is that they've been a tinkerers stove, with very few solid rules for building and everyone who sees them says to themselves "I can make this better!" without ever having made one by the book first.. My J-tubes work just fine, thank you! Yours should too!
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Post by Donkey on Feb 18, 2015 12:18:40 GMT -8
Does the new edition include details of horizontal box builds and the p/s chanel? No. It covers the basic J-tube only. In the back, there are case studies in which Peter van den Berg and I discuss the P-channel (in our separate pieces)
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Post by Donkey on Feb 18, 2015 1:47:00 GMT -8
I'm playing with ideas to create a system without using a stone (urbanite) foundation AT ALL. I'll probably build a tiny test structure this season. Cob directly on the ground with earth-works to keep away water. I know that conventional wisdom screams not to do this but I don't care! Just a few years ago, conventional wisdom said that Rocket Mass Heaters shouldn't work. So much for that. I know of one 300 year old cob building in Devon, England that is cob straight on the ground. Also, all over Africa, the Mid-East and the Far-East. I have historical support! All that's left is to figure the right set of procedures.
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Post by Donkey on Feb 18, 2015 1:29:21 GMT -8
The roof is a tension structure. Fir-pole framing, curved in all directions with plywood forced down over it. VERY light construction but also very strong. Waterproofing is supplied by pond-liner, cardboard layers under to protect and provide some insulation (don't need much in my climate), wood-chip duff over the top to protect from UV. Relatively inexpensive and long lasting (pond liner rated at 30-50 yrs).
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Post by Donkey on Feb 18, 2015 1:23:17 GMT -8
Instead of using fire it could be done chemically. Geopolymers?? Yes, that is VERY interesting.. On the other hand, earthen walls provide an internal air quality that is unmatched. It's cheap, reusable, easy to repair, has good thermal qualities, mitigates internal humidity and improves internal air quality. Seems like a high bar. I know of no other material set that will provide what earth does. It's only drawback is that it cannot sit in a puddle, so don't build with earth in a flood-plain!
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Post by Donkey on Feb 17, 2015 1:05:26 GMT -8
Frankly, I don't see the point. A roof is FAR simpler, cheaper, less wasteful and longer lasting.
I have heard that in Northern England, the old cob builders used to say: with a good hat and boots, raw cob experiences a "loss of face" of an inch per century.
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Post by Donkey on Feb 16, 2015 11:15:21 GMT -8
Not a problem as a foundation. Don't cover cob in concrete renders, that's where the failures happen. Here we are laying an urbanite foundation in May (or June) of 2013: And here is the finished building:
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Post by Donkey on Feb 16, 2015 11:07:45 GMT -8
Nader Khalili, founder of Cal-Earth tried this (back in the eighties I think).. He filled the inside of earthen domes with wood and fired them. The buildings were quite lovely, in some he set bottles in the ceiling that melted and made built-in chandeliers.. In the end, it was decided that they were a bad idea.. They really only fired on the inside so they didn't properly protect from the weather and the amount of fuel required was utterly ridiculous. To fire one completely inside and out, one would need something like a small forest in fire-wood. The idea was essentially sound but impractical.
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Post by Donkey on Feb 16, 2015 10:46:39 GMT -8
I think you will find (as I did) that the side air doesn't work as well as one would hope. What tends to happen is that it will blow smoke out the feed. The lid for the feed will get quite hot, wood will begin to pyrolyse up in the feed itself and every time you open the lid to add wood, you get smoke and sometimes flame streaming into your face. So far, it has been best to flow air over the top, down through the wood and into the fire. This can still be done with an external air source to good effect.. Also, it seems (so far) that if you want to be able to feed in more wood, the Batch-Box is a better option. Murphy's law has a particular thing for long pieces of firewood and tall wood-feeds.. They tend to hang up and fail to slide down. I don't use wood longer than about 3 fingers more than the depth of the firebox, I've had burning wood roll out and onto the floor too many times, after hanging up, burning away the base and toppling out..
On the other hand, If you find a good solution for the above issues, please tell the rest of us! Your experiences experimenting with these ideas will be valuable whatever the final outcome!! On that note, to ACTUALLY answer your question: with air coming in the side, the feed height won't matter, no.
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Post by Donkey on Feb 14, 2015 12:28:23 GMT -8
Ernie and Erica Wisner with Paul Wheaton are in process with another set of Rocket Stove instructional DVDs. In support of that, my good friends and the great work that is done over at Permies.com, lets help make this project happen!!
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Post by Donkey on Feb 14, 2015 12:08:50 GMT -8
Hello everyone. In an attempt to make the board more useful and respond to some requests that I've received, there have been some changes/additions.
There is a new set of categories under the heading of "Natural Building Techniques". This is by no means a complete list, if you want a new category added, ask and I'll gladly add it.
At the bottom of every page, you will notice that there is a "Shout-Box" where you can communicate (chat) in real time. I'm not entirely sure of the need for this service. If you like it, it can stay; if you don't use it or dislike it, let me know and I'll remove the thing.
Thanks! D-
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Post by Donkey on Feb 5, 2015 11:36:55 GMT -8
How about the manifold? I always look there first when these stoves have issues. The transition space, under the barrel, where gasses have to turn into the bench, that space should be much larger that you might think.
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Post by Donkey on Jan 29, 2015 8:10:18 GMT -8
No one really knows.. Those of you who live at altitude need to run the tests and report back!
It might be helpful if some folks, living at different altitudes worked together on this. Build identical test stoves, measure the output and compare.
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Post by Donkey on Jan 29, 2015 8:01:14 GMT -8
I really don't think that lime is going to do well in a rocket stove burn zone. Your mortar will turn back into quicklime at around 900 C. Easy temperature for rocket stoves. The clay/ash/fine sand mortar will do far better.. Use as little as possible, mortar is for filling uneven spaces only and where the bricks fit firmly, simply dipping them in clay slip should suffice.
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