Discussion in 'Back to Basics' started by chelloveck, Nov 16, 2015.
Interesting video @chelloveck. I do have one question regarding the bottom pot. It has a hole in the bottom and he has it in something. I wonder how much of a clearance you would need for the bottom hole.
Not sure...that may have to wait until I build one. I suspect that it is a source of airflow to feed the fuel.
My thoughts exactly. I was wondering about the ash etc.. also blocking the hole. Look forward to your report once you construct. I am thinking of trying this on a small scale just for a testing purposes.
Just to make things easier, you should be able to cut the bottom off the large pot in just a few seconds using an electric tile saw. A lot of the places that sell tile have a trim saw that customers can use for free. Alternately, an abrasive disk chucked in a hand drill should do the job easily. Once a hand saw gets dull, gnawing the rest of the way through the pot would be a bit tedious.
Likewise, cutting it with an abrasive disk on a drill press would be super-simple and would make a clean 90-deg. cut.
One of the later videos showed a guy cutting a pot with an abrasive jigsaw blade. That would work fine, too, but the cut should always be made under running water to keep the grit on the blade from getting clogged up with dust.
One other thing: vermiculite is a good, cheap, insulator--but it wicks up water like a sponge. So if the oven is outdoors, it'll need to have a waterproof cover or a lot of time and fuel will be repeatedly wasted in drying it out. Even sand will hold quite a bit of water.
An angle grinder will do the trick as well.
@UncleMorgan I was wondering why vermiculite for the reasons you said, why not just use sand and cover between uses?
@chelloveck if you figure out how to cook tandori bread, I'll make one
In one of the related videos that comes up after the first, another builder was using vermiculite because sawdust tended to char and catch fire.
Completely covering the Tandoor between uses should be be adequate. Any exposed insulation would tend to collect rainwater, unless it was grouted over.
I was thinking of setting a Tandoor up like a tea-trolley, and just wheeling in into a shed between uses.
Vermiculite has better insulation qualities than sand, less mass than sand, and the sand itself will draw quite a bit of heat from the cooking chamber.
Other improvements might be to seal the outer surfaces of the pots to minimise moisture penetration into the pot. Unglazed pots are porous and will absorb moisture. Enclosed moisture and heat are not a good combination...which may cause the pots to crack or shatter.
Lining the inside surfaces of the pot containing the vermiculite insulation with aluminium foil may help reflect some of the heat back into the insulated mass, keeping the internal oven temps higher.
Keeping the oven out of the weather is highly recommended. The trolley idea is an excellent one. It isn't difficult to find unwanted gas BBQ trolleys being dumped at municipal kerbside trash collections. Some modifications might be necessary to ensure that the oven will be stable and won't tip off the trolley when it is being moved.
Quite true, many rocket stove builders use vermiculite in their cob mixtures because of this.
I would really like to make this and I now have the pots but I do not have the vermiculite.
Sand would be great but it won't work. I really do not want to go buy vermiculite just to see if this works. I wasted lots of money on experiments. What about kitty litter? I can think of other things to use litter for if this oven doesn't work.
I do not know. There are several different kinds of cat litter, with different kinds of material as absorbent matter. I am not sure what affect heating it will have on each of them. Vermiculite can be used as a potting soil conditioner (for lightening the soil and improving irrigation and aeration.) Perlite is also a possible alternative to Vermiculite, having much the same characteristics. Perlite - Wikipedia, the free encyclopedia, both as an insulative filler and as a potting soil conditioner.
Vermiculite is a soil additive to hold water for plants. It should be available to you at your local nursery.
Perlite and vermiculite are very different materials and both can be a pain. One absorbs water and holds it and releases it, the other doesn't and floats on top of your soil in the greenhouse. Some are very dusty and the dust can be dangerous. Most growing mixes use vermiculite as a major component as it is cheap, light weight , and helps control the moisture levels. A lot of perlite is used in hydroponics as it does drain and helps get air to the roots. I don't know which would be best for an oven, but I hope that Bear and Chelloveck check in on this as they have very good ideas on both foundry furnaces and their insulation and on greenhouses and the use of vermiculite and perlite.
@Bear what do you think? ^^^^ I have the pots to make this but am hoping to use something for insulation that I have on hand and that is cheap!
Coarse Vermiculite, 12 Quart bag
Sorry but have to rant:
I am here to learn how to survive, use my brain and use what is on hand. I do not prep/store vermiculite. By saying only this be used and insisting this is it, that is teaching me to shop. Anyone can run to Home Dept but that is not what I need to learn. I know how to buy stuff. I can shop, I can shop anyone of you into the ground. What I am asking, what I want to learn is: what would be an item that is basic to most households that could be used? What about pea gravel? That is easily found and available. I know the natives used rocks to hold heat. What is a basic item that can act as an insulation?
Enough dirt is an insulator. However, you miss the point of vermiculite. It IS commonly in many homes, BECAUSE it is used in many gardens. One tablespoon of it in a cloth tube 18" long makes a "neck-buddy" used by many construction crews. (I have had many of these). It cools you while working out in the sun.
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