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Post by martin on Apr 13, 2008 11:24:16 GMT -8
Hi folks,
I just want to pose a question. I am seriously considering contructing an 8" rocket stove burner and using a masonry heater type of heat storage to hold the heat. We are limited on space, so the bench or bed-type thermal storage would use up a lot of space. Our house is 24' x 42', wood frame, wood floor w/crawl space and I wanted to construct a footing and a foundation, then lower the rocket stove below the floor level by 6 or 8 inches to try to gain a little room and build the thermal storage above and around the rocket stove with the exhaust going out through the roof. If you have any thought on this, whether it's feasible or not, i would appreciate your input.
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Post by Donkey on Apr 13, 2008 17:37:57 GMT -8
Great idea!
Just think carefully about your clean-outs. Fine white ash will tend to blow down-line and collect at corners and in wide spots. If you use piping, you could thread it up and down a couple times. The ash will collect at the bottoms of these runs, thus locating clean-outs in convenient spots.
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Post by Peter on Apr 14, 2008 11:44:23 GMT -8
Hi Martin, I've been pondering about such a contraption for weeks now. The best idea I came up with: a rocket stove inside a single or double bell. Actually, the exhaust would come out on floor level, so the chimney start really low. The bell itself would look like a large masonry box with the fire box inside it. The hot gases which come out of the heat riser would go up, where there is no way out and at the same time pushing the colder gases down and out. In case the exhaust temperature is too high, channeling it into another bell on top of the first one will cool the gases a lot more down. It's advisable not to have condensation inside, so the end temp should not come below 80 C, which is... 176 Fahrenheit. See stove.ru/index.php?lng=1 for a lot of information about double bell heaters. Hope this is clear, English is not my native language. |
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Post by canyon on Apr 14, 2008 16:57:20 GMT -8
Peter, Thanks for the link to Kuznetsov's Stoves!  I think it might take me a little bit to wrap my head around this bell shaped combustion chamber!  It took me a month of reading and re-reading the Rocket Mass Heaters book before I felt like I had a basic grasp to the rocket stove concept. Have you seen one of these? Do you understand the design? Thanks, Lasse |
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Post by Donkey on Apr 14, 2008 20:46:40 GMT -8
The bell stove thing seems like an interesting idea... If there were some obvious advantage I would say go for it.. I don't see one though. Instead I see a whole lot of complexity, designed to solve a problem (or problems) that rocket stoves don't have. The "bell" as described does seem quite a bit like a barrel placed over the heat riser.
Hmmm... Actually this site may help explain some of the odder behaviors I've witnessed in various tests..
Cool site. Lots of good info there. Much to be learned.
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Post by Peter on Apr 15, 2008 10:00:55 GMT -8
It took me a month of reading and re-reading the Rocket Mass Heaters book before I felt like I had a basic grasp to the rocket stove concept. Have you seen one of these? Do you understand the design? I do understand the design of the rocket stove as Ianto Evans build them. And I do understand the principles of a double bell heater. For a simple drawing: see www.stovemaster.com/html_en/designsystem.htmlThe whole system of free gas movement however, I am very suspicious about that. The bell principle do work, for sure. We experimented several weeks ago with a small contraflow heater. Made the expansion chamber three times higher than before, and the whole thing kept working. End temperature plus CO went down dramatically, efficiency went up by almost 15%. We do use a Testo gas analyzer for testing. It is best to view it (the double bell) like a heat exchanger where you could place your own wood combustion unit inside one of the bells. That burner could well be a rocket stove. The plan is to start with a single bell and a simple rocket stove. Perhaps not the Ianto Evans variant, rather the horizontal fed Winiarski cook stove built with refractory bricks. I do these things in my spare time and my resources are limited. Don't hold your breath for the results. |
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Post by martin on Apr 16, 2008 16:06:11 GMT -8
I thank you folks for your input, but I think I'm going to stay away from the double bell design. I thank you for the link, something to study when I have time.
What I kind of have in mind is the Ianto Evans rocket stove burner with the barrel. The exhaust would exit in two locations opposite of each other, then flow directly up channels to the top, then over the top and then down to the top of the cavity that would house the rocket stove. {A semi-contraflow design.} Above the cavity to the ceiling would be baffle chambers. At the top of the baffle chambers the exhaust would vent out of the building through a triple wall stainless chimney. Clean outs would be located at each exhaust exit from the barrel and on the sides of the downdraft channels where it turns into the baffle chamber. There would be four clean outs in all. That's what I have in mind at this point. Does this sound like an idea, or no?
Again, I thank you guys for your input.
Martin
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Post by martin on Apr 16, 2008 16:12:15 GMT -8
P.S. The other idea I had is that the outside casing would be brick, and the inside would be like the cob bench with stone, clay, sand and cob encasing the metal flue. This idea also appeals to me. I think it would be cheaper to build. This would be the same basic design as the other one, but with stone, sand and clay as the heat storage.
Just a thought.
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Post by Donkey on Apr 21, 2008 9:14:32 GMT -8
There is definitely something to the bell idea.. Looks like the barrel itself can qualify as the first bell. Especially if you add more space at the top, instead of an inch or so it would be like 6" to foot.. Perhaps you (peter) should join up here as a member and start a thread in the experimenters corner..  Back to Martin's heater.. I see no obvious problem with your design. Looks worth while. Can you give us images? Drawings of your idea and photos of your process?? I'd love to see how it progresses. |
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Post by martin on Jun 21, 2008 11:06:01 GMT -8
Sure, but I'm not sure how I upload the pictures. I have 3 .jpg images I'd like to upload, but don't know how. Would someone be able to help me?
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Post by Donkey on Jun 25, 2008 7:57:34 GMT -8
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Post by Donkey on Jun 25, 2008 19:40:24 GMT -8
I kinda like it. The only thing I would say is that the damper on the top COULD lead to trouble. The inclination to treat it like a regular wood stove and damp it down during operation is pretty high. Anyone who uses the thing will need careful training. Be SURE that it remains FULLY open during the entire burn cycle and is only closed after the coals go completely out. or... better yet.. omit the damper entirely. |
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Post by canyon on Jun 27, 2008 0:21:41 GMT -8
Looks pretty neat. Did you drop the barrel out of the concept? Did you also drop the split exhaust exits to a single? Why are you going six inch now? I think it would be wise to build your insulated heat riser in such a way as to be able to take it apart and repair/rebuild later without damaging the rest of the stove. Have you also studied David Lyle's Masonry Stoves book? Are you a mason? This is a pretty serious construction project. Where are you located? Did I ask enough questions? ;D
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Post by martin on Jun 27, 2008 17:16:14 GMT -8
Hey Canyon, I'll try to answer your questions. I did drop the barrel out of the equation because I don't have room for it. I would have liked to have used an 8" burner but our average winter night temperature on the eastern shore of Maryland is in the 20's, maybe dipping down to the single digits once in awhile, so I think a 6" should work fine. I have studied David Lyle's Masonry Stoves book and refer to it from time to time. I also have examined www.mha-net.org quite a bit, especially after they post the photos of their annual workshop. I am a tile contractor. I have not been formally trained as a mason, but I have been in construction all of my life, have done brick and block work. The split exhaust was going to be for the 8" stove, where the burner would have come in from the narrow end of the heater 90 degrees from how the 6" rocket will be situated. You have a good suggestion concerning the access to rebuild the rocket. I hadn't considered that. How long should a 6" rocket built with fire brick be expected to last? Under ideal circumstances I would build the rocket stove separate from the heat storage so that I could alter or repair as needed, but I just don't have the space. I also have a wood floor with a crawlspace, so it's very difficult to make a larger foot, hence the compact upright concept. Martin |
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Post by Donkey on Jun 27, 2008 18:53:54 GMT -8
The barrel really isn't necessary, it's simply a convenient, easy to use and cheap (or free) radiator for a more instant heat.. It is nice to have, otherwise you gotta wait for your storage to warm a bit before you get any human benefit. You could build (or find) a metal box that fits in somewhere convenient.. Run flue products through it and enjoy.. Or even possibly allow your flue pipes to surface for the same effect. You plan on doing the thing in conventional masonry?? Huh, I guess I didn't really see that before. Though now that you mention it, there it is clear as day..  Been busy lately.. Have you considered doing it in cob? |
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I think it might take me a little bit to wrap my head around this bell shaped combustion chamber! 
It took me a month of reading and re-reading the Rocket Mass Heaters book before I felt like I had a basic grasp to the rocket stove concept. Have you seen one of these? Do you understand the design? 
Been busy lately..