The masonry stove basically consists of 3 chambers.
Flap A is opened when the fire is lit. The exhaust gas goes straight into chamber 3 and out the chimney. When a good draft has been achieved flap A is closed (as the diagram shows). The exhaust gas is forced into chamber 1 and then into chamber 3.
The general principal is that in each chamber the hot gases rise and warm the building blocks. The cooler gases will then leave from the bottom of the chamber and enter the next chamber where the same will happen. Basically we are taking advantage of the fact that hot gases rise. Very simple really.
The advantages of this masonry stove is that:-
1. There is less resistance for the exhaust gas.
2. Easier construction.
3. More interesting shapes can be thought out.
4. When the fire is out there is less heat loss as always the cooler air is taken from each chamber to go into the next (or chimney at the end of its travels). The above is especially the case if the stove door is not totally sealed.
The building blocks of the masonry stove are laid dry without mortar. And once the first layer is level the next layers can be laid very quickly as a sprit level is hardly used. The masonry stove is then reinforced from the outside with metal wire and finished off with clay.
There is a patent pending on the way that this masonry stove is constructed. As far as I know there is not another one like it.
So far I have had very good results.
The masonry stove is very efficient. Even when I burn a hot fire the exhaust gases leaving are about 30 degrees. As the time goes on this rises a little as the temperature difference between the blocks and gas gets less.
I did get hair line crack at the back of the fire chamber. I smoothed it out again and is barely visible now.
The 2.5 ton masonry stove stays warm for 24 hours after one firing. The bench which is an extension of chamber 1 gets comfortably warm during (and a bit after) the burn but cools down relatively quick . It may need some more mass?
On the whole I am very pleased with the results.
It would seem that the internal air channels plus the duct going into the chimney should be of a greater diameter as the draft was a bit poor.
I have rectified this by setting a variable speed fan on top of the chimney stack and masonry stove works very well now.
Below is a timelapse movie showing the construction of the prototype masonry stove