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Post by patamos on Dec 17, 2015 8:10:30 GMT -8
Hi folks, Well, i have finally decided to convert the heat source for a community sweat lodge i built 10 years ago. Much as i love the ritual of bringing in the hot stones… i am drawn to find a (much much much) greater efficiency in harvesting the heat made by fire. Images of primordial nordic saunas come to mind... I still want to keep the lodge dark while pouring rounds, so the air feed will have to be tunnelled from outside. Has any one tried doing this? If so with what results/feedback/discoveries? All thoughts are welcome...
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Post by Vortex on Dec 17, 2015 13:34:18 GMT -8
The J would probably be the most responsive for controlling the temperature, and give just enough light to see for pouring water on. I've seen a few done on top of various types of woodstoves using the bottom 6 or 8 inches of a barrel cut off and filled with river stones. So why not make a J tube stove but cut the barrel off at the rib below the top, turn it upside down and clamp it on with a ring-clamp and fill the top with a load of suitable river stones.
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Post by patamos on Dec 19, 2015 19:17:46 GMT -8
Ahh, good idea with the stones,
I will probably place the 2/3rds of a barrel low in the ground, and set the j-feed tube down low as well. Might place a 1/2" of clay rich cob on the top of the barrel and splash on to that. I love that smell of clay drying out…
My question now is how best to provide air to the system. I would like to cap the feed tube with a lid to make the lodge as dark as possible, so will be ducting air in underground. With all the recent discoveries to do with chet portals and re-evaluation of what primary and secondary air is about… i wonder what would be the best way(s) to inject the air in to a j feed. My guess is mid way along the burn tunnel…
??
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Post by Vortex on Dec 22, 2015 11:17:47 GMT -8
With all the recent discoveries to do with chet portals and re-evaluation of what primary and secondary air is about… i wonder what would be the best way(s) to inject the air in to a j feed. My guess is mid way along the burn tunnel… ?? www.permies.com/t/52176/rocket-stoves/Add-air-intake
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Post by patamos on Dec 22, 2015 19:45:58 GMT -8
Thanks Trev,
So maybe primary air from the top of the feed chamber, and maybe some around the front for the p channel. Kind of like What Sandy and co at dragon heaters have been doing...
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Post by Vortex on Dec 23, 2015 9:48:04 GMT -8
I think that's about the best you can do with the J tube. Much more and you end up having to redesign it to the point where it isn't a J tube any more.
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Post by patamos on Dec 24, 2015 7:32:33 GMT -8
Ya, I agree.
Another factor i am noticing as i play around with a J-feed (in an addition i am building onto our little house…) is that any air coming in from lower down tends to increase the possibility of reverse airflow up the feed tube. Just a reminder that all the experimenting done so far, especially by Peter, has likely optimized the design
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Post by Vortex on Dec 24, 2015 15:17:07 GMT -8
That's what I found as well, came to the same conclusion.
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Post by Donkey on Dec 25, 2015 15:12:03 GMT -8
I thought about this one quite a lot, before building my first, sweat lodge based sauna. My build is here on the forum someplace, I wouldn't bother looking it up, as you're not likely to learn much from it at this point. I fooled around with external air intakes, looking for a method to satisfy the needs of the fire, while also keeping as close as possible to the traditional sweat pattern. In the end, my client didn't want the external air intake, so it didn't happen. It was still quite good for me, as I learned a lot about the J-tube feed at that time.
As you guys already know, air pretty much has to come in at the top of the feed and flow down through the wood, otherwise it will cause smoke-back. Sometimes, when the stars are aligned, bottom air can be made to work, but for me it was a MUCH bigger hassle with no guarantees than it was worth.
One configuration that I tried that never failed, was to bring air in next to the feed and bring it to the top in a brick channel right beside the regular feed and at the very top, the brick between the two can be shortened. This makes a gap that air can flow through between the channels at the very top. This way, a lid can be placed all the way across the two, blocking the light without blocking airflow. With the lid off, air tends to come from the room, but no matter how the lid is placed, the fire is never deprived of air, it never smokes back, etc.
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Post by Donkey on Dec 25, 2015 15:21:23 GMT -8
Oddly enough, I just found an image in my stuff that has that air intake in it.. You can pretty well disregard most of what's going on here, it's OLD and most of the ideas I was working worth have since then been shown to be bogus. In the image you can see the brick base, on this base there are 3 openings. the larger, leftmost opening was for the heat riser (again, experimenting with stuff that didn't turn out) The one in the center (labelled 6 3/8) is the feed and the one on the right (labelled 2 3/8) is the external air channel. To get outside air, you just drop a lid over the two channels (feed and air).. Of course, you need wood that is cut shorter than the feed...
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Post by patamos on Dec 26, 2015 9:15:20 GMT -8
Thanks Donkey,
If i build a 6" square feed tube, do you think a 2" x 6" air feed would suffice? Not sure how i'll configure a P-channel, unless it all can happen under the same lid…
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Post by Donkey on Dec 26, 2015 12:35:41 GMT -8
I believe that the accepted ideal air intake size is still 1/3 system CSA.. That would be my minimum.. Actually, I'd make all of the ducting and channels right up to the firebox base somewhat larger, then build just the base itself to spec. That way, if for some reason it has insufficient air, changes would only need to be made to the one area. I think that oversizing most of the ducting would help to avoid friction problems as well.
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