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Post by jeanlou on Nov 13, 2016 16:08:45 GMT -8
I just saw your message, and would be happy to talk about kilns. I have not built an actual rocket fired kiln, but I have built a dozen or more iterations of a wood-fired kiln which has similarities to rocket design, and a rocket-fired bake oven. I could see modifying the oven design to bring the fire directly into the chamber, enlarging the firebox to give the rate of heating required. I have photos of my latest and best kiln and the oven, for a base to work from. I'll have to do a bit of fiddling to get them all hosted in one accessible place. Hi Glenn, and thank you, I will look forward to seeing your photos. I've been busy getting the property ready for winter and had to put the kiln build on hold. The kiln's about two thirds done, I'd say. I'll post some pics of the progress so far as soon as I get a better grasp of the pic-posting procedure.
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Post by jeanlou on Nov 13, 2016 16:15:53 GMT -8
Hi Guys, this is neither exactly a Raku nor a rocket kiln, but it´s got interesting similarities to rocket stove technology, since the fire burns downwards and there is no smoke even in a reduction atmosphere. The firebox is called Bourry Box style. I also like the hinge mechanism of the insulated firebox cover. Hi Ralf, thank you for the great video. That is quite the beast! Very impressive. Like you I found the lid arrangement very clever. How many pieces were there in that one bake?
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Post by jeanlou on Nov 13, 2016 16:33:37 GMT -8
That is a beautiful kiln! I looked through Robert's thread, and what he did is very similar to what I was thinking. I would just go with a firing chamber with a cutout side and door of refractory material, instead of a lift-off top. Another possibility for a raku kiln would be to have the top on a hoist system so it could be raised up (by a crank and pulleys?) to reach the ware. This would allow free access, which I have found valuable when trying to pick up hot pieces with tongs. It would still keep some heat in the area while moving the pieces, so the last ones don't cool so much before putting in the smoking can. A raku kiln I used long ago had a very simple top made of ceramic fiber in a wire cage (very light) which was picked up off the base and set aside, using two people with a pair of 2x4s to hold under the handles. Of course, this would not be practical at the height of a rocket burner. All this is very interesting, there are myriad ways of approaching the design aspect. We're going with a hybrid "barbecue smoker" kind of approach, with a 6-inch stainless steel insulated stove pipe rocket L-tube set in a vertical 55-gallon steel drum, feeding heat into a horizontally placed 55-gallon steel drum bake chamber lined with ceramic wool. Pics to come that will make it all clearer. We should start testing next weekend and our first objective is to replicate Robert's temperature levels. Can't wait!
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Post by jeanlou on Nov 14, 2016 21:27:14 GMT -8
Here's a view of the inside of the bake chamber, seen from the L-tube firebox side
...and from the exhaust chimney side
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Ralf
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Post by Ralf on Nov 16, 2016 21:24:30 GMT -8
Hi jeanlou, I don't know how may pieces they got in the bourry box kiln at one bake, I´ve never been there but I imagine it would be fun to help them firing one day. I also heard of a wood-fired Raku kiln that`s made of a metal garbage bin lined with ceramic fibre insualtion. It´s got an opening for loading the kindling-sized wood fuel at the bottom and is an updraft kiln with a short chimney mounted to the lid of the bin. Pictures can be seen here, the text is in German though. I met some potters who said that they reach 1350 °C / 2460 °F with this thing easily. The soft fibre sheet is fixed with ceramic knobs on the inside that are sewn through to the bin wall with Kanthal wire. By the way, this would be exactly the method that I would use construct my future heat risers for rocket heaters. I´m courious how your build will perform, it looks promising. Good luck ! Ralf
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Post by jeanlou on Nov 17, 2016 9:24:33 GMT -8
Thank you Ralf.
We did pretty much what you describe: ceramic fiber lining, ceramic knobs, Kanthal wire and all. Now you got me thinking about using that approach for my next riser too! 😎
We did a first firing test with a gas burner yesterday afternoon and reached 987° C, enough for most raku glazes. After about 50 minutes, our 20 pound tank got too low on gas and covered with frost, and the temperature stopped climbing so we ended the test there. We're gonna get a 60 pounder and try to get to around 1270°C.
After that, we will redo the same tests using small wood sticks, like Robert did, then pellets. So far we're pretty pleased with all this. I'll post pics of the inside of the finished bake chamber and of yesterday's test soon.
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Ralf
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Post by Ralf on Jan 17, 2017 4:50:09 GMT -8
Any news from the ceramic rocket kiln, I wonder if it was a success ?
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