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Post by oldbat on Mar 4, 2014 10:11:54 GMT -8
No need to slink away from your soapbox Sparks, those were some excellent points that needed making! Happen to be on a slab, and our house is not as fancy as most. We already heat with wood and the wife is as tired of cutting and splitting wood as I am... Ain't no way a 7,000 LB 'stucco couch' is going to happen here either:-(
Should we start a thread for non-cob masses? I have an idea for a long straight bench that might be worth kicking around.
Oh, hi I'm new here.
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Post by talltuk on Mar 4, 2014 14:02:53 GMT -8
A lot of different mediums have been kicked around on here. The thing is, they are MASS heaters. This means most mediums are blasted heavy. Some have used cement, some have boxed them in. You can eliminate the mass and just have a large metal radiator like peters batch barrel bell, or do low mass by building say a metal bench and using these storage heater bricks. Maybe not good for lo ger heatig though, griz might know. I think a large bell might be lighter but takes up more room. Water is the most commonly used in regular homes but is dangerous when heated by solid fuel without care paid to saftey features. My two plans are to experiment with an accumulator/thermal store heated by water and a small skirtingboard heater made to the magnetite bricks
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Post by DCish on Mar 5, 2014 4:07:35 GMT -8
I had at one point thought about setting up a 4-incher and running it more continuously, but then again, without the mass I'd be back where I am with my box stove, constantly feeding it. I do have a slab to work with, so I'm back to planning a mass stove. One compromise might be a sort of baseboard tunnel of brick around the perimeter of a room to really spread out the mass well.
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Post by patamos on Mar 6, 2014 18:38:54 GMT -8
Matt Walker posted a while back about his fairly low mass half barrel approach to building benches. On one project in New York he built a long bench by laying many of the barrels end to end with permanent wooden forms front and back, and covered the half barrels with dry earth. Then (maybe?) placed a skin of cobb plaster over the top deck of it. Could be done with wood or w.h.y.
For the nat build beginners: 3 parts coarse sand, 1 part fine sand, 2 or 3 parts thick clay slip, 3 or so parts fine chopped straw... can be mixed in a tote with a heavy duty drill with a egg beater bit. So long as you get the mix right it is very easy to spread around and shape contours with. Sandwich some loose-weave clay-soaked burlap with 1/2" cob either side and you will create a very strong surface.
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Post by Vortex on Mar 7, 2014 1:56:55 GMT -8
Storage heaters are hung off the walls for this exact reason so why not do it with the mass for a rocket?
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morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
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Post by morticcio on Mar 7, 2014 2:41:43 GMT -8
Storage heaters are hung off the walls for this exact reason so why not do it with the mass for a rocket? Good point... it kind of leads me on to a plan going round in my head for my basement in Italy. The room is open plan with the existing wood burner & chimney in the corner. I want to put a Peter-style batch box more the centre of the room and I also want to 'partition' off the kitchen and seating area using a 12" (30cm) wide brick wall approx. worktop height (900mm or 3ft). The wall will be 1800mm or 6ft long. I'm thinking if I widen the wall slightly and 'hollow' it out, it can act as the bell (or second bell). A bench along the back wall will hook up to the chimney in the corner. This creates a 'wall heater' or 'heat wall' - the wall is the mass. Hopefully you can picture this from my description, if not I'll see if I can get a drawing done in Sketchup. Edit: I got the idea from the Lopez Labs rocket-bell experiments. Here is the link |
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Post by 2tranceform on Mar 11, 2014 7:12:20 GMT -8
OK now I am going to go out on a limb here and question the current paradigm...cob. Has anyone done any experimentation with ANY other substance to act as a heat battery besides cob? .... You need mass to store heat. Without massive mass attached to the stove, you will need to heat by radiation and convection. This has been done before. Incorporate a larger bell that is light weight (1.5 barrels, sheet metal bell, etc) and extract as much heat as you can before exhausting. You could also build something like this.... link. It is substanially lighter that a cob bench and allows efficient heat capture. The cob bench is the classic rocket accessory, but there are many ways to skin a rocket.  |
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Post by sparks on Mar 13, 2014 19:02:17 GMT -8
OK now I am going to go out on a limb here and question the current paradigm...cob. Has anyone done any experimentation with ANY other substance to act as a heat battery besides cob? .... You need mass to store heat. Without massive mass attached to the stove, you will need to heat by radiation and convection. This has been done before. Incorporate a larger bell that is light weight (1.5 barrels, sheet metal bell, etc) and extract as much heat as you can before exhausting. You could also build something like this.... link. It is substanially lighter that a cob bench and allows efficient heat capture. The cob bench is the classic rocket accessory, but there are many ways to skin a rocket. While I do understand that cob is the current "mass" of choice, I am asking about whether there is any other material that will perform as good or better than cob but not be as large or as heavy? We all know that water has the highest DELTA G of any substance and running the exhaust pipe from the rocket heater through a water mass would work safely with the exhaust gas temperatures in the under 150*F range. It would not become hot enough to boil or create steam and if kept at 120*F would provide adequate heat exchange for a period of time. I'm just asking because I don't know. This is not meant to be rhetorical. |
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Post by DCish on Mar 14, 2014 6:39:18 GMT -8
Lots of posts discuss this issue. Donkey has on more than one occasion pointed out that even though water can hold more heat per unit mass, with its low phase change temperature, it reaches capacity at such a low temperature that one pound of cob at 400+ degrees is holding considerably more energy than a pound of water at 212.
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Post by Donkey on Mar 14, 2014 21:52:28 GMT -8
Large and heavy (heavy at the VERY least) is the basic definition of thermal mass..
Water does have the best specific gravity, but ALSO presents enough complications to make me not want to deal with it except for rare specialized purposes..
Really, anything that's heavy, unwieldy and doesn't conduct TOO well makes for good thermal mass.. Soapstone is considered to be one of the best, masonry is good, field stone good.. Cob is mostly used 'cause it's cheap (soapstone is NOT cheap) and can be made into ANY shape easily.
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Post by satamax on Mar 14, 2014 22:34:46 GMT -8
Donkey, it can also conduct heat well, and be insulated on the outside, so the heat release is slower. Or at least i think this is also possible. The insulation can be removed too, for faster heat release. As everybody does with their cushions or matresses on the cob couches.
Something which i've said for a while, a concrete with lots of stones. I don't know about the States, but here, concrete is cheap. I can make a cubic metre of it for 70 euros. Or may be even cheaper for a rocket bench, which doesn't have to whistand much effort. If made well, it can also be self suporting.
Well, enough babble.
I'm off to work.
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Post by Donkey on Mar 15, 2014 23:30:58 GMT -8
Yep. You can use lots of big rocks and concrete. It's heavy enough.. A bit more conductive than cob, so heat will move through faster.
Many of us greenies frown on the use of concrete, but it will work just fine if kept away from the high temp areas.
Strategically covering and un-covering the bench (mass) with insulation, (pillows, blankets, etc) is a well worn path that has been shown to work.
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Post by talltuk on Mar 16, 2014 1:47:39 GMT -8
On that Donkey, I was considering using fly ash cement for benches as an easy to transport solution. It uses fly ash from blast furnaces and powerplants to replace portland by up to 70%
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Post by mintcake on Mar 16, 2014 10:26:31 GMT -8
On that Donkey, I was considering using fly ash cement for benches as an easy to transport solution. It uses fly ash from blast furnaces and powerplants to replace portland by up to 70% Are these pre-cast breeze blocks / cinder blocks? If so, don't I remember that they are fairly gas permeable? |
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Post by talltuk on Mar 16, 2014 13:37:44 GMT -8
Nope this is straight up cement. I think it might only be available premixed delivered but not sure. I would use it to cover half barrel benches as well. Given some
consideration to limecrete as well but I think that has less thermal mass and more insulative
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