- Case: make or customize
- How are combustion chambers
- Simple and convenient “ash pan”
- Installing the combustion door
- Flue duct and draft control
Many are faced with the need to organize heating in small utility rooms. Here, efficiency, compactness and expediency of financial costs are important. A long-burning potbelly stove is ideal for heating change houses and garages, and our instructions will help you with making it yourself.
Case: make or customize
Firewood in a stove for a long time does not burn, but smolders very slowly. At the same time, a highly heated pyrolysis gas generated due to the thermal decomposition of the fuel burns in a chamber adjacent to the firebox. In this “strangled” operating mode, the furnace does not generate very high temperatures, so the metal can be quite thin – about 2.5 mm. Naturally, with full air supply, the stove will be heated red-hot, so if you want a high power mode, make the case massive.
The duration of the stove operation between the tabs depends on two factors: the mass of the stored fuel and its combustion activity. Therefore, you should not expect that a compact garage oven will be able to work up to three days, it simply does not have enough fuel for such a period. The ambient temperature also plays a role: the lower it is, the more actively the combustion process takes place.
Sheet steel is ideal for making the body. It is also possible to use any profile rolled products, folded in vertical rows in a ring or rectangle. There is a problem in weld all the seams, but in this case the stove receives multiple stiffeners and gives off heat as efficiently as possible.
The stove body is made very simply: blank sealed walls and bottom. Loading can be vertical and horizontal, in the latter case the top cover plays the role of the fire door. We will consider both spatial positions of the potbelly stove, but the body will be unified for each. For example, let’s take a 50 liter propane cylinder with a cut off top – a cylindrical body has the advantage of more uniform heating.
Scheme of operation of a long-burning stove with a horizontal combustion chamber. 1. Chimney damper. 2. Door flap. 3. Combustion chamber. 4. Pyrolysis gas afterburner chamber. 5. Stove door
Scheme of operation of a long-burning stove with a horizontal combustion chamber. 1. Air supply damper. 2. Chimney damper. 3. Air supply pipe. 4. Combustion chamber. 5. Stove cover. 6. Pyrolysis gas afterburner chamber. 7. Piston
How are combustion chambers
To obtain the coveted pyrolysis gas, it is necessary to almost completely limit the flow of oxygen into the main furnace, where a high temperature center is formed, leading to the transition of carbon fuel into a gaseous state. The minimum air required for slow smoldering enters the furnace due to various leaks.
Putting the balloon horizontally, divide the circle in height into 4 parts, apply it to the cut edge of the mark and mark the length of the upper and lower chords. According to the obtained size, we cut out a steel plate 3 mm thick. Its length should be 150 mm less than the body depth.
Having stepped back from the short edge of the plate 100 mm, we weld a transverse partition with a height of 150 mm and adjust it in shape to the cylindrical body so that the plate is directed to the center of the firebox. We put in place and weld the plate, forming a residual combustion chamber.
Potbelly stoves with vertical loading have a different principle of operation. Their combustion direction is opposite to the natural one – from top to bottom. The stove itself has a syringe device, the piston of which is made of sheet steel, or lids from a barrel or cylinder with bent edges. It is important that the “piston” enters the body as tightly as possible.
From the bottom side, several distance ribs are welded onto the plate from a conventional 50 or 75 mm angle. A hole is cut in the center of the plate and a 75 mm pipe is welded through which the required minimum of air will flow. The principle of operation is clear: the piston sags under its own weight as the wood burns, leaving a small space for pyrolysis decomposition. Air flow is regulated by a damper at the end of the pipe.
Simple and convenient “ash pan”
In a potbelly stove of long burning, an ash pan is not needed, a small amount of light ash after combustion remains directly in the firebox. But you can still adapt the stove for easier cleaning, especially if you plan to add coal to the firewood..
1. Stops from the corner. 2. Lattice above the “ash pan”
When the stove is placed horizontally, you need to cut out the same plate that was used to form the upper chamber. Instead of a partition, it has a usual 35 mm angle welded transversely. In the front part, a handle is made from a thin bar. The plate is mounted on two guide angles welded along the body. For a tight abutment of the plate and exclusion of strong air leaks, it is recommended to do this:
- weld the corners under the bottom of the plate with shelves upwards on small tacks that are easy to beat off;
- insert the plate into the body and weld the corners to the walls, filling the thick weld seam well;
- introduce scrap into the lower chamber and undermine the plate, if possible, clean up welding marks.
Through small slots, the minimum oxygen required for combustion will enter the chamber..
1. Disk. 2. Holder made of reinforcement. 3. The side of the “ash pan”
For a vertical potbelly stove, you need to cut out another flat disc and weld a piece of thick steel reinforcement to it in the center. A steel strip rim is bent and welded along the perimeter of the circle. In both cases, ash removal is carried out after the stove has cooled down: the ash pan is removed, cleaned and installed in place before a new laying.
Installing the combustion door
We grab a steel strip to the body of the horizontal potbelly stove and wrap it around, forming a ring. It is necessary to trim the edges several times so that after welding such a mandrel sits very tightly on the edge of the body. The ring is welded to a cut off lid from a barrel or cylinder, or to a steel sheet, then the seam is carefully welded outside. The strip should protrude about 12-15 mm above the surface of the lid, this is enough for a tight narthex, at the same time the firebox will open relatively easily.
On the inside of the door, several steel plates are welded to form grooves for the internal partitions of the firebox. The door itself, due to the annular porch, must be installed on a remote canopy, respectively, the pressure lock must also be moved to the side by 40-60 mm.
1. Cover. 2. Air duct with damper. 3. Canopy
When loaded vertically, the lid acts as the outer wall of the afterburner chamber, therefore, it does not require careful sealing. The edges of the vertical body are bent inward with a hammer, the side of the lid, on the contrary, needs to be flared a little. In this case, it is important not to bend the lid itself, then the abutment will be tight under its own weight. A hole is cut in the center 1–2 mm larger than the diameter of the air supply pipe.
Flue duct and draft control
The discharge of combustion products in a horizontal stove is carried out in the upper part and as close as possible to the firebox cover. It is recommended to use a pipe with a diameter of at least 150 mm for the chimney. The air is supplied through a sleeve welded through the door, which goes into the lower chamber by 70–100 mm. It is better to use ready-made blocks with a damper to adjust the air supply. Quickly and in place, you can weld a small bolt to the pipe from the outside, which will tighten the disc damper.
The chimney of a vertical potbelly stove cuts in the same place in the body, but now, accordingly, it is located horizontally. If you drill a through passage and pass a pin through it, on which a round plate is fixed, you can get a damper for adjusting the thrust and full control of the fuel combustion process.