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Post by DCish on Dec 16, 2018 18:18:36 GMT -8
I have noticed a lot of temperature increase when I lay a cf blanket on the stove top. I'm not sure if others have played with that idea, but it is a fairly easy way to control where the btus are used. I use a soapstone batch box to feed a bell bench. I have dry stacked a bunch of bricks behind with a 1" air gap, and I use angle iron on top to create a half inch air gap on top of which I stack more mass. Even with the air gap, the mass soaks up the majority of the heat until they warm up, which greatly smooths out the heating curve. I don't insulate the stove directly, since the soapstone surface is supposed to stay below 500F or risk cracking it. Frustrating, but one if these days I'll finally build my own core...
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Post by permaculturebob on Dec 16, 2018 18:46:23 GMT -8
I cracked the first soapstone batch box cover I had and finally found a piece of cf board which I used as the top part of the bb roof, and then a 1"cf blanket, with soapstone on top--that one lasted out the season and i'm pretty sure it allowed for increased temps in the bb.
I never knew soapstone was only good to 500f--thanks for the info, although I did figure out that whatever temps I had were way too hot.
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Post by DCish on Dec 17, 2018 6:31:55 GMT -8
The 500F number is from the stove manufacturer, so my guess is that there is some degree of safety margin built in. I keep a thermometer on the stove top, and I have definitely strayed above that at times, at least as high as 550, maybe 600, but I try to avoid it. Having the blanket below it probably helps smooth out how quick it comes up to temp. Since it is temp differential that causes cracking, that probably means you are pretty safe with your setup.
As for my ultimate build, the next prototype I have planned is a DSR that feeds from the side, with stovetop glass on top. It is still in the conceptual stage, but I do hope to run a rough prototype over the winter. If I do, I'll be sure to open a thread on it.
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Post by Vortex on Dec 17, 2018 7:20:56 GMT -8
As for my ultimate build, the next prototype I have planned is a DSR that feeds from the side, with stovetop glass on top. It is still in the conceptual stage, but I do hope to run a rough prototype over the winter. If I do, I'll be sure to open a thread on it. I look forward to that. If you haven't already have a read through the experiments I did over a couple of months last summer: donkey32.proboards.com/post/30273/thread Is your idea of a side loader to get a bigger view of the fire?
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Post by permaculturebob on Dec 26, 2018 6:39:07 GMT -8
The double shoe box is elevated off the floor about 18 inches, and instead of an exhaust on top- in front, it is channeled horizontally under a glass stove top from left to right. I'm not quite sure who it was here that suggested having the water tank inside the bell, but it was that idea that led me to my design, which in appearance is like a glass stove top, with an extended simple porcelain covered metal counter top. This extended bell houses a naked 20 gallon water tank with two fittings, one for cold water at the bottom and one for hot at the top. The top fitting connects directly into the hot water feed for my house system, and while in operation the hot water valve to the shower head in my tub is left open, and the cold water flow to the tank is shut off. This allows excess pressure to escape safely, and notifies me when the water is hot as steam starts to escape. Note that this is primarily proof of concept, and not yet ready for prime time water heating, it could easily have safety features added that would further ensure a more automatic type system. Last night I was burning the third batch of wood in the firebox, low grade poplar and some mystery wood, likely not completely dry, when I started to hear the steam. That produced a luxurious long (10 min at 4-5 gal/min), very hot shower (mixing lots of cold water). I was concerned about stratification, and the possibility that all the water would not heat evenly, but the length and relatively constant heat of the shower indicated this was not an issue. The design inside takes the combustion gases exiting under the stove top into a very broad vertical opening that directs the hot gases forward into a circular motion around the whole vertical surface of the tank, with some small horizontal space over and under the tank. These gasses that are further cooled start to sink to the bottom as they circulate. The "stack" entrance is below the bottom of the tank in back of the system, so the exhaust comes in contact with about 270 degrees of the surface of the tank, with some minor contact top and bottom. Note that this stack is actually a powered exhaust by a very cheap, low wattage (about 10)fan. This provides a more or less guaranteed exhaust even at startup, and the exhaust is so cool (around 100F) that more robust (and expensive) equipment is not needed.
The test run last night reached temperatures on top of the port between 900 and 1000 F during the third batch of wood, with a very robust secondary burn at the port. Without testing equipment I have no way of knowing just how clean this is burning, but it appears that the system gets more efficient into the second and third batch of wood by the size of the secondary burn. Perhaps using insulated Fire brick at the port would get the port to temperature quicker (it is currently standard , full fire brick), and adding ceramic fiber blanket over the stove top might also enhance the temperature build up by reducing convection and radiation losses there.
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Post by peterberg on Dec 27, 2018 7:03:29 GMT -8
An hour ago I've found this video by Uncle Mud of the first complete DSR cookstove. Built in 2017 but wasn't completed that year, as far as I know.
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Post by Vortex on Dec 27, 2018 10:01:40 GMT -8
Nice. Where's the primary air supply on it? There's no sign of it on the front.
I see he's got the wood at 45 degrees. I found that was the best way, it keeps the fuel nearer the port for longer, which they seem to like, and burns up the face of the wood gradually working back towards the rear bottom edge, which is always the last bit to burn.
Odd how it was uploaded Nov 6th and had 2 views when I looked at it. Also it's not listed in Muds videos, how did you find it Peter?
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graham
Junior Member
Posts: 74
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Post by graham on Dec 27, 2018 12:09:09 GMT -8
I'm curious as to why the flame fountain is going straight up and not diving towards the chimney? Is the because the top chamber is a box so the draft overall is lower inside there?
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Post by peterberg on Dec 27, 2018 13:30:57 GMT -8
Nice. Where's the primary air supply on it? There's no sign of it on the front. In the design it is placed at the right hand side, there's small opening visable under the casserole door as well. I see he's got the wood at 45 degrees. I found that was the best way, it keeps the fuel nearer the port for longer, which they seem to like, and burns up the face of the wood gradually working back towards the rear bottom edge, which is always the last bit to burn. I've tried half a dozen placements back in 2017. At home, while the Testo was coupled to it. The best placement seemed to be from front to back and nothing else. Some other configurations looked better mind you, but according to the Testo they weren't. To start it up quickly your method would be probably best. Odd how it was uploaded Nov 6th and had 2 views when I looked at it. Also it's not listed in Muds videos, how did you find it Peter? I found it on an obscure website, don't know which one at the moment. When you run it directly from YouTube you'll see it's hidden, that's why. That website got hold of the link somehow I'd think.
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Post by peterberg on Dec 27, 2018 13:36:16 GMT -8
I'm curious as to why the flame fountain is going straight up and not diving towards the chimney? Is the because the top chamber is a box so the draft overall is lower inside there? Yes, it's because the top box is large enough to slow the velocity down. I suspect the heater is just started some 10 minutes ago. When running at full tilt the view is much more like a powerful blast.
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Post by peterberg on Dec 27, 2018 14:07:29 GMT -8
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Post by DCish on Dec 28, 2018 8:37:44 GMT -8
As for my ultimate build, the next prototype I have planned is a DSR that feeds from the side, with stovetop glass on top. It is still in the conceptual stage, but I do hope to run a rough prototype over the winter. If I do, I'll be sure to open a thread on it. I look forward to that. If you haven't already have a read through the experiments I did over a couple of months last summer: donkey32.proboards.com/post/30273/thread Is your idea of a side loader to get a bigger view of the fire? Oops! Sorry I missed this post somehow... and the experiments you linked to as well! I'll post there on my reactions to that content. As for this specific question, the space I have to put the stove is constrained by the fact that I have already built the mass bench beside my commercial box stove, and I don't have permission to build out into the room any further, so my stove footprint is shallower than it is wide. If I can avoid a riser tacked on the end, I can orient the stove with the side facing out, and it fill fit the space perfectly. Aesthetics are important too, so having a larger fire viewing are would be an added bonus, and if I put a glass in the side of the afterburner too, I'd get a huge fire viewing area!
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Post by permaculturebob on Jan 14, 2019 16:03:22 GMT -8
Just thought I would post a simple experiment I did with my dsr with glass cooktop, just laying a partial CF blanket on top over the port, and it increased the temperature by two hundred degrees on top of the glass, pushing more heat farther along under the top, including the water tank bell at the far end before the stack. I knew that would raise the temperature, but the difference was more than I expected, especially with such a short test. Likely with a longer test and a full blanket the difference would go even higher. I got the circulation pump hooked into the plumbing,and initial tests circulating water to the radiant floor were promising, but I'll need to wait for tomorrow to do some better testing. The next questions to be answered are about the heat exchange to the water tank, and how much extra heat to send to the water tank bell before it starts wasting heat up the stack. I also need to find a place to install the thermostat sensor to turn the circulating pump off and on
And today I finally broke down and ordered some neoceram for viewing windows, and will take better pics of the fire after I get it installed. I paid 105$ for two pieces 3/16" x 10"x10" and wondered if that was a good price or not.
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Post by Vortex on Jan 15, 2019 9:55:35 GMT -8
That's about average for the stove glass. I would think any ceramic or steel stove top subjected to the intense heat directly above the port is going to radiate a lot more instant heat than an insulated one, especially when combined with a ceramic glass window on the end of the same chamber. I would also think it's not going to give as efficient and complete combustion as an insulated one. That instant direct heat in one spot is obviously beneficial in a small dedicated cooking stove, but maybe not what you want if you need to heat an oven, bell, bench or water as well. Maybe you could get hold of some of those old insulated stove top covers like: THESE That would give you more control of where the heat goes and when.
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Post by likeithot on Jan 31, 2019 9:36:47 GMT -8
Thanks for your posts. I thought the DSR was just right for my situation too, then found that it wasn't recommended, so I'm watching & waiting. Maybe a sidewinder will work for me.
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