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Post by wiscojames on Oct 9, 2014 10:32:19 GMT -8
My apologies if this has been addressed elsewhere - I have not seen it. I have decided to use my 6 inch mud batch box ( donkey32.proboards.com/thread/1350/first-tries-batch-box ) to power a mud oven. The question I am struggling with now is whether or not to treat the oven as a bell. In the case of Date Farmer's oven ( www.youtube.com/watch?v=uR-LqOquLZA ) the heat enters the bottom, is diffused with a plate upon entry, then exits the top (also making use of a diffuser plate to slow the exit) into a chimney. What about the idea of exiting to a chimney at the bottom of the oven so that only the coolest air is exiting the oven. Seems like a good idea, but I'm looking for some persuasion one way or the other. The only downside that I can see now is that it won't look as graceful as having a chimney centered in the top of oven. Thanks in advance! (Let me know if I need a sketch to serve as a visual aide.) |
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Post by satamax on Oct 9, 2014 10:45:52 GMT -8
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Post by Daryl on Oct 9, 2014 10:52:22 GMT -8
The warm gases are going to be drawn to the cold. If you have side by side hot/cold entry/exits, then you might not get the best performance.
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Post by matthewwalker on Oct 9, 2014 12:00:04 GMT -8
I've had great success with the oven as a closed chamber set on top of my barrel, with an adjustable opening to allow the hot gasses into the oven allowing precise temperature regulation. I can bake at a broad range of temperatures with good control while the fire burns. It's a great system, I can bake at lower temps for baking or roasting, on up to pizza oven temps, all with excellent control. It's not really a bell, and it doesn't have a chimney of it's own, but it works amazingly well. So, to answer your question, neither! It also does a great job of keeping the ash out of the oven, which is a huge plus.
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Post by wiscojames on Oct 9, 2014 12:23:39 GMT -8
Wow. You guys are good! (And charge an affordable hourly rate.) So either direct the incoming stream of heated air away from the exhaust, or just eliminate the chimney altogether? Wouldn't that second option mean that the door would become the chimney? That would be fine, I guess, since I was envisioning charging the thing up and then using a door while cooking. In that case I suppose I would want to keep the door opening relatively low to avoid much of the heat escaping right away? The difference is that you are cooking while burning, and I'm not sure that I will be, with a batch box. You were talking about cooking in that way with a J tube, yes?
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Post by matthewwalker on Oct 9, 2014 12:58:03 GMT -8
Batch or J, no difference. The door isn't really a chimney, I provide the gasses an alternate path, down the barrel in a classic riser-and-barrel RMH configuration. You can bleed heat into the oven by adjusting the opening. Here's the basic build... ....Then build your oven on top of that. You can then add heated seating, or another burner, or whatever. Here's how the one in that video ended up...   |
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Post by satamax on Oct 9, 2014 21:43:48 GMT -8
I've had great success with the oven as a closed chamber set on top of my barrel, with an adjustable opening to allow the hot gasses into the oven allowing precise temperature regulation. I can bake at a broad range of temperatures with good control while the fire burns. It's a great system, I can bake at lower temps for baking or roasting, on up to pizza oven temps, all with excellent control. It's not really a bell, and it doesn't have a chimney of it's own, but it works amazingly well. So, to answer your question, neither! It also does a great job of keeping the ash out of the oven, which is a huge plus. Matt, admit, when the port on top of the barrel is open, it's a bell  A single port, if big enough can act as intake and exhaust of the bell at the same time. Tho, i don't know how it works with a hole about four inches!
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Post by matthewwalker on Oct 9, 2014 22:08:46 GMT -8
Ha! Whatever it is, it works incredibly well. I can fire it up, bake some bread and roast some veggies at 450°, take them out, bake a pizza at 700°, turn it down, pop in a cake, and hold it at 350° for 30 minutes. I've made cookies, cakes, roasts, pizza, bread, you name it. It's amazingly controllable. Here's a pic of the thermometer receiver, with one probe in the oven while the other is in the smoker on the second burner. Same fire...  Pizza...  Peanut butter blackberry cookie...  |
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Post by wiscojames on Oct 10, 2014 4:56:56 GMT -8
Love the system, Matt. I want one. Yesterday. So that might very well be a project next summer, but for now I am rushing to try to get one small project completed. Hard frost last night, and it's only a matter of time before we get sucked into another polar vortex. (Oh, to have the Pacific Northwest climate...)
So I have my mud batch box in place, plan on building an insulated riser atop it, then a mud oven on top of that. No barrel, no bench (I had thought of harvesting the residual heat in a small bench, but it is not at a convenient height for that.) So, if you were only doing that small project, a simple mud oven, fired from below, would you go chimney-less, with a chimney in the center of the top of the oven with a deflector plate to slow the exit of hot gasses, or a chimney low on the side of the stove, along with some sort of deflector plate that would direct the entering heat away from the exit? (and maybe a deflector plate to slow the exit) Or???
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Post by Daryl on Oct 10, 2014 5:33:33 GMT -8
The pros will give a better answer because they will base their information on rocket stoves. I prefer a front top flue over a center flue. This allows the entire ceiling to absorb the heat and later radiate while cooking. No flue at all will also be as beneficial. Examples:   |
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Post by wiscojames on Oct 10, 2014 5:56:01 GMT -8
thanks Daryl - I like the layout of both of those - the double chamber with the chimney in the outer chamber (which in effect makes the oven into a bell) is something I am considering now. Nobody is sold on the idea of a low exiting chimney that elbows up to vertical? Even if I incorporated baffles to prevent the heated air from traveling directly to the exit, and also a mechanism to close off the chimney once heated? Again, I will not have a live fire here. I am looking at charging up the mass of the oven and then shutting it down to cook.
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Post by matthewwalker on Oct 10, 2014 8:25:50 GMT -8
Love the system, Matt. I want one. Yesterday. So that might very well be a project next summer, but for now I am rushing to try to get one small project completed. Hard frost last night, and it's only a matter of time before we get sucked into another polar vortex. (Oh, to have the Pacific Northwest climate...) So I have my mud batch box in place, plan on building an insulated riser atop it, then a mud oven on top of that. No barrel, no bench (I had thought of harvesting the residual heat in a small bench, but it is not at a convenient height for that.) So, if you were only doing that small project, a simple mud oven, fired from below, would you go chimney-less, with a chimney in the center of the top of the oven with a deflector plate to slow the exit of hot gasses, or a chimney low on the side of the stove, along with some sort of deflector plate that would direct the entering heat away from the exit? (and maybe a deflector plate to slow the exit) Or??? I would definitely drop a barrel over it and put the exhaust in the barrel like I show in the video. You need something to hold the oven up anyway. It is the simplest option in my opinion. I came up with it when trying to figure out how to make an oven stand on top of a riser. It solves all the difficulties of a system you are describing and gives you far better control. |
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Post by thickstrings on Oct 10, 2014 9:46:46 GMT -8
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Post by Daryl on Oct 13, 2014 1:56:50 GMT -8
![]() ![]() Daryl, here's my version. Built a brick house around the dome and super insulated it....hot for days
Well, I can't view the pictures. Maybe it is me.  Hope you come back through, thickstrings.
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Post by Donkey on Oct 13, 2014 7:08:14 GMT -8
thanks Daryl - I like the layout of both of those - the double chamber with the chimney in the outer chamber (which in effect makes the oven into a bell) is something I am considering now. Nobody is sold on the idea of a low exiting chimney that elbows up to vertical? Even if I incorporated baffles to prevent the heated air from traveling directly to the exit, and also a mechanism to close off the chimney once heated? Again, I will not have a live fire here. I am looking at charging up the mass of the oven and then shutting it down to cook. When we built the rocket oven this summer, we went for the bell-style lowered chimney. There was excess heat so we were able to build a little hot water heater off of the final exhaust as well. So far, I like it. I think we should have made it an 8 inch system instead of 6, it would respond FAR "snappier" that way. With the lowered chimney, you can choose which way the heat goes.. With the oven door open, it will vent out the door which makes starting easier and with the door closed, it seems to heat faster AND (with mine) it routes heat down through the hot water heater. The cooking complex we built this summer can be seen at: donkey32.proboards.com/thread/1301/all-adobe-mud-cookstoves-ovensMatthewwalker's oven is very much bell-like, it looks utterly golden to me... Another vote FOR bell-style ovens. I would like to see side-by-side tests, it would be interesting to identify the differences between models, their strong and weak points, etc. |
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Hope you come back through, thickstrings.
