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Post by martin on Jun 28, 2008 15:28:18 GMT -8
I have considered making a flat steel surface above the heat riser in some manner, and stepping back the brick to make a little cooking area, but I decided to do this on a future model. I did consider building it out of cob, but I have never worked with cob before. In the future I expect that I will build some out of cob, but I'm starting with the materials that I'm familiar with.
By the way, I wonder if anybody has used tiles in heat-type applications with any success? I have done heat tests on many different tiles. They all heat shock and bust, with the minor exception of very soft-bodied tiles.
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Post by canyon on Jun 29, 2008 0:30:42 GMT -8
I haven't used tile yet but I am planning on it on part of my mass bench. How are you heat testing them? I don't plan on mine getting any hotter than 140 F being several inches from the flue through cob and set on a two inch lime/cement/sand plaster. Of course there are nice heating tiles from Europe but expensive. Those jar tiles with the extra surface area like in Lyle's book sure are cool.  |
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Post by martin on Jun 29, 2008 2:59:58 GMT -8
Canyon,
Your lime, cement and sand sounds like type N mortar, which is regular brick mortar. It should work pretty well, but if you get any cracks in your cob it may transfer through your tile. In testing, I have built a couple of model masonry heaters out of tile. I put tiles in different degrees of fire. The tile you do not want to use on your masonry stove is porcelain tile. It heat shocks really bad, especially with uneven heat. I think that basic tile, below 200 degrees as a maximum should do well.
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Post by jpmanley on Aug 25, 2008 0:29:06 GMT -8
A proper damper is essential to hold in the heat produced from a burn, otherwise the firebox heat goes up the chimney overnight instead of into the house. We (the MHA) specify that any damper installed in a masonry heater has a 5% opening even when closed. In Europe it is illegal to install a damper without such a opening. The purpose of the "gas slip" is to allow escape of Carbon Monoxide from the firebox even after the fire looks like it is out, but is still producing CO. Generally, most people who own a masonry heater, understand that they are using a different sort of wood stove, and understand the principle of an open flue during a hot burn, and damp down after the fire is out, not during a burn. Pat I kinda like it. ing 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 martin on Sept 8, 2008 16:40:25 GMT -8
Thank you, Pat, for your input on my project. I do value your opinion and your experience, and if you see anything in my design which may be in question please let me know. I have the guts of it mostly constructed. I need to finish my downdraft and connect the heat riser to it. I still have to install a chimney. I would like to do a test burn or two to test for leaks and any trouble spots that may crop up before I fill with cob and complete my brick shell.
Thanks to all for helpful information.
Martin
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Post by Donkey on Dec 9, 2008 8:17:13 GMT -8
Hey, Hey!! Here are some pics of Martins finished product. I personally love the creative use of the cast iron pot. Just too dern cool.     |
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Post by peterberg on Dec 15, 2008 11:48:30 GMT -8
Looks good! Separate air intake, internals not connected to outside wall, as far as I can to see.
regards, Peter
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Post by martin on Dec 15, 2008 17:07:08 GMT -8
If you mean the air intake, it is connected to the outside so that it brings in fresh air. However, it's not enough fresh air to keep it burning when the pot lid is closed. The idea is so fresh air can trickle through the system to allow carbon monoxide to escape when the dampers are shut down. I also am using the fresh air duct to help equalize the wind pressure, but I have not had any problems with wind pressure at all.
The combustion is burning at about 1,800 degrees F., as checked by heating a piece of mild steel and comparing it to a chart with corresponding temperatures. I have measured the exhaust temperature at the top of the chimney in the center of the gas flow at 180 degrees F.
The stove is doing a wonderful job of heating our 1,008 s.f. home when the temperatures are above 30 degrees, and it does a good job heating 50% to 2/3 of the house when the temperatures are below 30 degrees. (We have a long hallway with bedrooms off the hallway and the stove is in the large living area of the house. No mechanical air circulation is being used.) The stove's surface temperatures behind the heat riser and downdraft tunnel generally range between 105 to 145 degrees, depending upon how often I fire it. Where the steel 6 inch pipe with cob filler (mass) is, the temperatures generally run between 85 and 105 degrees. So far, we're very pleased with it.
Martin
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