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Post by Solomon on Jan 23, 2021 8:46:18 GMT -8
I've been planning this for years, and I'm finally getting to the point where I'm about ready for construction. So I built a practice core in the back yard out of Craigslist clay brick. Yes, I have already sacrificed several because they keep cracking in the burn tunnel. But they were cheap and the learning experience is valuable. I documented my progress here: www.youtube.com/watch?v=mMRqY8XMiR8Lessons: First time around, I unconsciously assumed that clay bricks were the same dimension as fire bricks. They are not. So I did not get the burn tunnel height or length right. Second one is with proper dimensions. Air sealing is important. When wood is stuck up in the feed, blue smoke. Not enough air, black smoke. I'm getting the same problem that I get with my Solo Stove Yukon. Eventually it fills up with coals and chokes off with not enough draw. Must empty ash with every burn. I don't know if this is common with J-tubes, but I have seen the rams horn flames that peterberg talks about with batch boxes. But only when running rich. I stuck a barrel on top, trying to burn the paint off, didn't work, not hot enough, not enough draw. So I had to help it with a propane weed burner torch.
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Post by pigbuttons on Jan 23, 2021 16:25:29 GMT -8
That's much better draw than most other loosely stacked stoves I've seen. An ash pan below the feed tube will greatly ease the burden of clean out, but yeah, ash production is intense. The coals also take some time to go to ash, (hours in fact), and as they stack up in the bottom it is the same problem of blocking the entrance to the burn tunnel cutting down on air flow.
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Post by Solomon on Jan 24, 2021 7:43:24 GMT -8
That's much better draw than most other loosely stacked stoves I've seen. An ash pan below the feed tube will greatly ease the burden of clean out, but yeah, ash production is intense. The coals also take some time to go to ash, (hours in fact), and as they stack up in the bottom it is the same problem of blocking the entrance to the burn tunnel cutting down on air flow. I feel like the riser being insulated (and also really leaky) would produce even more draw. Now you've got me thinking I need to design in an ash pit into my CFB core. But it has a much larger burn tunnel than a constant cross section unit has. 8.5" deep by 7.625" wide. Allowing for a minimum of a constant nominal cross section (8" system) that means I can have about 2" of ash through the entire burn tunnel before any constriction happens. The test core has been burned four times with only one minor cleanout without nearly that much.
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Post by pigbuttons on Jan 24, 2021 12:25:46 GMT -8
That's much better draw than most other loosely stacked stoves I've seen. An ash pan below the feed tube will greatly ease the burden of clean out, but yeah, ash production is intense. The coals also take some time to go to ash, (hours in fact), and as they stack up in the bottom it is the same problem of blocking the entrance to the burn tunnel cutting down on air flow. I feel like the riser being insulated (and also really leaky) would produce even more draw. Now you've got me thinking I need to design in an ash pit into my CFB core. But it has a much larger burn tunnel than a constant cross section unit has. 8.5" deep by 7.625" wide. Allowing for a minimum of a constant nominal cross section (8" system) that means I can have about 2" of ash through the entire burn tunnel before any constriction happens. The test core has been burned four times with only one minor cleanout without nearly that much. In my experience of two winters of running my stove, it's just the floor of the feed tube and about the first two inches of the tunnel entrance that coals and ash accumulate enough to restrict flow. I don't expect that having a sunken feed tube floor would affect anything else in the overall operation of the stove and may even help in the early phases with a 2" step up to the burn tunnel, providing a trip wire type of turbulence where there usually isn't any. Once it fills with coals it is moot, but will give you about another two hours of continuous burn time. What I was thinking as far as a ash pan is to have the firebricks that make the floor of the feed tube to be able to pull out and maybe have the first brick on the front wall of the feed tube to be removable as well. you could then pull the first brick of the front wall and slide out the floor of the feed tube to remove the majority of the ash. Of course if you are enclosing all of it in cob that makes it problematic. If you made that front wall out of firebrick and stuck them to a piece of CFB and attached a durable surface to the outside of the CFB I guess that the whole front wall of the feed tube could be made removable and just gasket it with standard fireplace braided rope gasket. .
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