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Post by patamos on Jan 16, 2014 23:19:35 GMT -8
Thanks Robert, Your positive spirit is contagious  Well, after hearing all the bad news about regular portland cement-based concrete and heat... i have opted to 'treat' the underside of my pavers/bench deck with a cob-mesh-cob lay up.  The concrete was rough and porous enough for a good slip bond. I just hope gravity and any difference in behaviour of the cob and concrete under thermal cycling... doesn't cause delamination. Anyone with good or bad experiences on the matter please pipe up at will With temperatures ranging from -5c at night to +5c mid day, drying techniques came to mind... Discarded silviculture seedling trays have herein found yet another application. I think i am bound to write a '101 re-uses of...' book for these things. I moved the little woodstove out today. Prepped the burner deck and am turning my thoughts to that end of things. Some questions coming to mind include: What is the most effective and durable ash pit cleanout that people are relying on? My onsite-builder-friend Dan brought me a 1/4" x 5" threaded pipe cap today. I could see wrapping it in 1/8" ceramic felt once or twice... But man, that thing is gonna wanna move at the bottom of such a high temp downdraft chamber. So, ya, i am very open to alternatives. (b.t.w. to answer Donkey's original question on this thread: The main reason for the downdraft on one side only is due to space restrictions and proximity of wooden post and stairs.) Another question: I'm hoping to place a sheet of glass in the burn chamber. 10" long by 5" tall. I know it will reduce combustion temps, but aesthetic value trumps that. I see casting the outer (room facing) burn-chamber wall as a monolithic post-beam-post. 1.5"x1.5" thick with a dado to the outside so the glass can be slotted in with ceramic gasket. (Wondering about 2 sheets of glass with a gasket spacer?). Then carefully cobbing the outside. Wondering if this is sounding whacked?!?! Any and all feedback is appreciated. Also, as i approach a final decision about how i will build my heat riser... i am leaning again towards casting a 1"thick circular 6" to sit on top of a square 6" burn chamber. Looking to wrap it in ceramic felt then 3" of clay perlite and containing it all in a brick outer box, one side of which serves as the inside wall of the down draft chamber. If i snug the riser forward and round the back corners of the burn chamber i might be able to effect the back sweep and kick tail effects that Peter describes. Might place a full width high temp. firebrick on edge and carve the belly out a bit to effect the kick tail in the middle. For the corners my sense would be to form the curved transitions out of clay, screened perlite, and super 3000 masonry cement (sodium silicate i think). Matthew, do you have a ratios recommendation for this application? Oh and btw, on a logistical note: I have tried sending picture files at different quality and size settings, but haven't figured out how to make them appear larger in the posts. Suggestions please? thanks for all your interests and inputs well being pat |
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Post by matthewwalker on Jan 17, 2014 0:41:31 GMT -8
I'm really enjoying following your build and thought process Pat. Thanks for bringing us along with you!
As for pics, it's so much easier to host them elsewhere like Photobucket or other photo hosting site, then use their link code to post the pic. You won't have to worry about size, they have thumbnail links or full size, and we can click on them to expand or see your album.
Don't do the dado! Trust me, I learned that the hard way. A few times. Just capture the window tight against the burn chamber wall. I've captured it with ceramic fiber insulation,then top coated with insulating cob. I've also just schmucked it right there with insulating cob. I've stuck a couple masonry screws in the core to make a ledge for it to sit on, then left if floating in there, kinda captured with some fiberglass rope that squished it tight held by the outer layer, which in your case could be bricks. I used hardiboard and tile, on my outside heater. I think that using your advanced mud skills and mesh/mud composites you'll get it right. Just keep it outside and separate from the cast burn chamber or they will tear each other apart. Also, the beam span across the window header is the weak point here. Get some of your mesh involved there if you can.
The sodium silicate is really forgiving in the mix. Make your normal mix a bit dry and use the masonry cement as the wet agent. You don't need much, just a fraction of the total. You want it to be mostly clay/perlite so it's stable once fired. You really can't go wrong, it'll work.
As for the cleanout, are you talking about at the bottom of the downdraft, before the flue run? If so, I'd just use another T and a regular cap. That heavy steel is going to break itself out of there in my opinion, especially once you start wrenching on it. Regular flue caps work great here.
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Post by patamos on Jan 21, 2014 21:52:17 GMT -8
Hi Folks,
Thanks Matt. Yes the clean out is for the ash pit at the base of the downdraft chamber.
Well, after a few days of nose to the grindstone i have pulled a few more pieces together. One of the biggest challenges has been the poor drying conditions. Most days i have 3 power cords coming off a 6000watt generator feeding 3 heaters, a couple of lights, 1/2" drill, and my lil' old makita grinder. When we (3 others on site) run out of gas... things pretty much hit a stand still. I have put the propane flame weeder on fresh cobb to solid it up and keep it warmish during -5c over nights.
All in all, something of a hydrocarbon hypocrisy.
Anyway, most of the cob-paver bell tops are in place now. The flue to bell and bell to chimney transitions are complete
And i have gotten a start on the burn chamber today. I found some fire bricks rated to 3000f to use in the back of the burn chamber, but they quickly reduced 3 of my $40 diamond tip discs to molten metal. Shifted lay up strategy there.
I also had an alarming surprise when the (new product for me) Clayburn castable refractory cement began setting up almost immediately. There I was with 30" of 6+" inside 9" sona tubing to fill. Suz (client) hopped in to help tap things into shape, but it was an ugly time. We'll have to see tomorrow, and I won't be surprised if it is a little patchy here and there.
Note to self and others: when the supplemental literature that comes with the product says it is 'gunnable' that may = very fast setting.
All in all, I must say, this attempt to squeeze everything snug up to a staircase and around a couple of posts has posed some fair challenges. ULtimately i have had to work room-ward from the staircase post, but still try to keep it all tight so the bench doesn't turn into a kingsize spread. Looks like it will fly alright in the end. It will just end up being a sort of love seat, which is fine with the clients.
We're all on the look out now for an old slab of cast iron for the griddle deck. Might be mild steel in the end.
btw. my attempts to load pics are now being met with a message saying 'this forum has exceeded its attachment size limit'. Is there a cumulative maximum Bytes per thread? Some of the above pics were on the large size...
Guess it is time to learn photobucket anyways
well being
pat
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Post by patamos on Jan 22, 2014 22:01:15 GMT -8
Wrapping up today for a spell of time back home with my family
Still seem to have reached my attachments limit.
Does anyone know how to delete a few high res pics from earlier in the thread?
well being
pat
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Post by 2tranceform on Jan 23, 2014 7:04:13 GMT -8
Very nice write up pat! Photobucket is pretty easy to use. Try it, you'll like it, lol. I can't wait to see the progress.
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Post by Donkey on Jan 23, 2014 8:40:42 GMT -8
Wrapping up today for a spell of time back home with my family Still seem to have reached my attachments limit. Does anyone know how to delete a few high res pics from earlier in the thread? well being pat You should be able to edit your own posts. |
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Post by patamos on Jan 24, 2014 20:35:18 GMT -8
Thanks Trance and Donkey, It may be the luddite in me, but when i go to remove one of the double images in certain posts they both disappear. I'll putter a bit more and then get into this photobucket thing soon anyway. For now i have two boys (monkeys i'd say) climbing all over me well being pat |
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Post by patamos on Jan 24, 2014 22:34:38 GMT -8
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Post by 2tranceform on Jan 27, 2014 10:10:01 GMT -8
Works great! Seems that I may need to look into homeschooling a bit more... lol!
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Post by Robert on Feb 17, 2014 1:51:29 GMT -8
How is the progress Patamos  |
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Post by patamos on Feb 17, 2014 10:26:57 GMT -8
Hey gang. Thanks Trance. Nice smiley Robert I've yet to get back over to finish it. Thought i'd be there by now but got wrangled in to helping a friend wrap up a big(ger than she thought iit'd be) finish plaster of a house. That and emergency repair of my neighbour's septic system... And 10 million other things... I am heading back to finish it in a few days and am beginning to think seriously of how best to create the double skin for the downdraft chamber. ONce the gasses go from the heat riser to bottom griddle deck i want to send them all to one side and down. Planning to surround the heat riser in ceramic wool and then 3" of clay perlite held in by a brick perimeter that will also support the griddle deck. On the downdraft chamber i am thinking of cobb on the surface closest to the heat riser and bricks for the outer side. Then 1/4" of ceramic felt, then 1" of cobb, then 1/2" fiberglass mesh, then another 1/2" of cobb. I think i have a good sense of where things will want to expand and contract... and how this approach will keep the outer skin tight. But i am less sure about how the inner skin of brick build up will fare over the long term. One question is whether to set them tight with furnace cement or with a bit thicker clay sand mortar??? ideas are most welcome thanks for following this post pat |
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Post by patamos on Mar 5, 2014 21:46:43 GMT -8
Alright folks, After 6 days in a very cold house i brought it very near completion. After 10 minutes of cranky wet start up it took off like a 'rocket' The bypass damper works great. Everything doing what it ought to. I had to depart before it all had a chance to fully dry out - not to mention the whole 1600' of house with many a wet brown-coated wall... The crux of the biscuit, and the crux of this thread's title was how to stabilize the downdraft chamber. As you can see in the photos it was a bit of a patchwork quilt. I opted to mortar the brick pieces together with a silica sand-clay, as furnace cement just didn't seem to fare as well with all the moisture coming and going as i went about drying segments with a propane flame weeder torch. Outside of those joints i laid a skin of 3/4"+ of cob plaster with fine chopped straw. Dried the cob a fair bit to shrink it down. then bedded strips of 2" x 2' fiberglass mesh in thin layers of mortar, taking care to overlap and wrap in various directions. So far it seems to be holding up well. I opted to oversize the feed, burn and HR dimensions to 6.5"x6.5" CSA. The downdraft and first 4' of primary flue are roughly double that. after which it all goes where i was hoping it would, including readily up the 6" CSA flue. Whew. more of the stories in the photobucket pics. apologies for the double images. couldn't figure out how to delete them... (sigh, yes i am a luddite) s895.photobucket.com/user/patamos/library/?sort=3&page=1 |
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Post by matthewwalker on Mar 5, 2014 22:50:31 GMT -8
Dang man, that is so nice! The window looks great, and I can tell the heater is working properly as it already has animals all over it. Nice work!
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Post by Robert on Mar 6, 2014 9:24:09 GMT -8
Yes. Super nice. The window reaches a little bit of a burn tunnel right? And what is your riser made of?
Nice job:)
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Post by patamos on Mar 6, 2014 9:50:29 GMT -8
Thanks guys,
Ya i was surprised at how quickly it took off when still wet. This was probably doe to the extensive vertical flue run above, but also maybe indicates that i have some heat to spare. We'll see once i get back there and things are dried out. Maybe a small bell on the upstairs floor.
The clients are super jazzed. Their first experience of hanging out on a conductive heat source
I placed the window where the feed tunnel transitions to the burn tunnel. Lined it with ceramic felt and insulated cob on the outside.
The heat riser i cast using cardboard sona tubes. And a castable high temp refractory mix from a company called clayburn. My first cast i discovered that the material wanted to set up super quick. So i did another one in stages. 6.5" ID, 3/4" thick. 28" tall.
Many thanks to you guys and everyone else who offered input. Having this kind of open source support community is so valuable:)
well being
pat
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