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).