The power of the powerless

Russian Ovens.... http://eng.stove.ru/products

So much to learn about masonry heaters https://www.youtube.com/watch?v=gaXyWyDm2mk

How about a strainless steel food grade sawzall blade?

So there are two main types of this kind of stoves. And difference between of them is how heat moving in stove's body.

First - when heat pushes by difference of pressure between inside and outside, and heating of the stove mass is happening because of friction of hot air and inner stove channels. I guess, rocket stoves working by that principle. And main goal of mason is to maximize area of hot air contacting inside channels. But main cons of this type of heating are: 1. you need more fuel tо heat up and hold your stove warm in long period of time in comparison with next type; 2. top part of the stove is heating more (probably even overheated), than bottom. It’s happening because of physics principle of tendency of hot air to go up. So if bottom part is less heated, your legs most likely will be little cold (if you don’t have warm floors, of course).

Second type is engineered different. Imagine, if smoke after furnace, where fire burns, goes into clay pot that turned upside down. Hot smoke goes up, than, giving off heat to the walls, cools and becomes heavier and tries to escape from below. Next, we place another inverted pot on top, this time larger, above the first one. The warm, new smoke from the first pot displaces the cooled smoke into the second, larger pot, where the heat is still transferred to the walls of pots rather than escaping, working like in the first pot. After which, the finally cooled smoke goes outside (in the oven - through the pipe, placed in bottom of second pot). Here the principle of operation is based on the transfer of heat through infrared radiation, so it is more effective than the previous one through friction. This happens because the smoke has time to cool down and release more heat. And also bottom part of the stove also heated due to the fact that the heated gases descend under their own weight. This is how Kuznetsov’s stoves works, in general. He’s not inventor of technology, but he improved it greatly. Main con of these stoves is their complexity. But for good mason this is not a problem. Even if you got any experience with masonry, there are a lot of drawings and tutorials on the web that will helps.