dkeav
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Posts: 27
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Post by dkeav on Feb 24, 2014 18:52:56 GMT -8
I was curious what the chances would be of precast concrete surviving as the bell in place of barrels like in Peter Berg's single bell test set up for the batch box. Precast concrete culverts in large sizes can often be gotten very cheaply from leftover projects and an opening for a batchbox could be cut fairly easily with a masonry blade/saw. A cap could also be casted rather easily this would provide a quick/cheap amount of mass for such a set up. I was just curious what the thoughts were on whether such a set up would survive the heat in the bell. Example of precast culvert
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Post by satamax on Feb 24, 2014 22:21:52 GMT -8
Well, concrete starts to fail at 400C°, so it could be good. I've thought about this before. Never tested. I wouldn't use it for the barrel. But why not for a second bell. There's the problem of diferent expansion rates of concrete and metal. Otherwise, i'd say, go for it, try it. May be an outside test set up as a bell. Or over a J tube dug in the ground. Like this you don't drill it before you know what it can cope with.
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Post by Vortex on Feb 25, 2014 2:31:28 GMT -8
I suggested this before, for the barrel you'd need to line it with refractory, better as a 2nd bell as Max says.
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Post by ronyon on Feb 25, 2014 8:29:59 GMT -8
I found an old laundry sink made of concrete, thinking it might be a good bell.
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Post by satamax on Feb 25, 2014 9:01:12 GMT -8
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dkeav
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Posts: 27
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Post by dkeav on Feb 25, 2014 11:34:17 GMT -8
I would be curious if a large enough bell would keep the temps to around 300C or so. For example I can get 42 inch (inside diameter) by 6 feet in length pipes that are around 3-4 inches in thickness for free to maybe $150USD. With two sections stacked that would be a very large bell and should keep the heat inside fairly even, though I would be curious if it would draft well enough.
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Post by satamax on Feb 25, 2014 11:47:57 GMT -8
12 square metres of ISA for the two pieces. So that's too much for anything 6 or 8 inch csa i would think. One would do for a 6 batch box.
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dkeav
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Post by dkeav on Feb 25, 2014 12:58:10 GMT -8
Well you could take a concrete saw and cut one down to proper size. So I imagine the best solution in this case would be to take some cheap flashing to make a form on the inside diameter and fill that area with a light refractory to handle the heat.
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Post by 2tranceform on Feb 25, 2014 13:11:50 GMT -8
.....So I imagine the best solution in this case would be to take some cheap flashing to make a form on the inside diameter and fill that area with a light refractory to handle the heat. Or use a trowel-on insulative refractory product to protect the portland from the heat.
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dkeav
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Posts: 27
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Post by dkeav on Feb 25, 2014 15:03:15 GMT -8
I wonder if 1/2" kaowool affixed to the concrete surface would be an ideal solution. Seems cheap enough and easy to work with.
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Post by satamax on Feb 25, 2014 19:07:06 GMT -8
Or inside sleeve and sand, a barrel inside and relying on convection. There's many options i think. Pile up some refractory bricks inside, as the Mathieu did. Many many options.
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kpl
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Post by kpl on Feb 26, 2014 1:57:47 GMT -8
Would concrete work for lower section of the bell, when the hotter upper part would still be steel barrel? I was thinking to use concrete street border blocks, which are extremely heavy but cheap as dirt. That way the stove's upper part would provide instant heat, but lower part would store a lot of heat for later. Those blocks could be stacked to create rectangular box, probably with just some kind of wool as gasket, without any mortar at all. That should work fine for workshop where good looks is not a requirement.
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Post by grizbach on Feb 26, 2014 10:50:52 GMT -8
kpl, Yes, you can use concrete for the lower bell. In fact I have concrete at the top also. It is bonded with refractory to isolate from the heat.
I made a sealer/mortar from rockwool/ash/and water. You could use this for bonding your bricks.
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Post by stephenson1 on Mar 4, 2014 4:06:06 GMT -8
Griz, could you give some details about your experience with a rockwool/ash/water sealer/mortar? Proportions, qualities is has, and how it shrinks, holds up etc.? Did you literally paste it onto the interior of your concrete bell?
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Post by grizbach on Mar 4, 2014 8:42:02 GMT -8
stephenson, I forgot to add clay slip to that recipe list. I used slip and ash as mortar to seal the pavers on the horizontal surfaces. I don't remember the ratios, but remember that it took a lot of ash. I kept adding ash until I got a thick consistency. I have a wider gap between the vertical surfaces of the pentagon form to fill. I used this same slip/ash mix and soaked pieces of rockwool in it. I used this as caulking and pushed it into the crevices.
This mix when dry, is porous and would allow vapors through at high pressure differences. With the low pressure of chimney drafts though, there has been no leaking. Since this is like a dense stone filter, if there were any leaks, I would think it would get plugged eventually by the ash in the exhaust. Any Pressure towards the bottom of the bell would be negative anyway.
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