Clay → Brick → Stove

    In this article I want to describe my experience in working with clay, making bricks from it (in a 1: 6 format) and creating a reduced model of a typical PTO-2300 heating furnace .


    Let's start from childhood. I grew up in a house with stove heating. I chopped wood, the firebox of the stove, the flames in the firebox, the noise of the wind in the chimney in the winter, the nuances of adjusting the draft by the blower and stove dampers I absorbed from an early age. Return to the opportunity to sit again at the fire, tossing firewood was possible only in adulthood. At the same time, a desire was born to deal with the design of furnaces; their types and purpose; operation features; the difference and advantages / disadvantages of one type of heating from another.

    The reduced format, some miniaturization, was chosen deliberately - with the same cognitive effect, we win in terms, volumes of materials used, efforts made, transportation costs, required areas, etc. And you can always increase the scale.


    The oldest natural resource discovered by mankind. Anything was built from it: wall and roofing materials, stoves, houses, structures and constructions, household and kitchen equipment, toys, crafts, works of art. It is everywhere, it can be obtained in any locality, the available reserves are huge.

    For several months of research, I managed to find three clay quarries in the immediate vicinity (and I found out about three or four potential ones, but did not visit). In them I dug clay of different quality and color. I purchased two more types of refined professional modeling clay in a store. The color palette of clays in nature is very diverse - from white and black - to the whole spectrum of red-yellow, as well as green, blue, etc. By the way, green clay was the first to meet me only 200 meters from the house!

    The most important thing if you start to extract clay yourself is to clean it from sand, organic impurities, garbage and other inclusions. To designate this process, a special term has been coined - elutriation. The technology is very simple: the accumulated clay is dissolved in water and passed through a series of sieves with an increasingly small cell. Large particles are separated, and at the exit we have a suspension with fine particles of clay. After settling, draining excess water and finally drying the clay, we get raw materials for further experiments.

    You can store the finished clay in plastic bags (without losing the desired moisture) for years. And so this product does not spoil at all - over time, it only gets better.


    Blinding a few bricks by hand, I realized that this is an unnecessarily laborious way. In addition, the spread in size was too critical. It was necessary to undertake the manufacture of molds, introduce standards.

    In parallel with the manufacture of forms, I "combed" the Internet, articles and books on the subject of what technology can make bricks massively and quickly. The oldest and simplest is manual molding. Extruding clay mass using screws or hydraulic pushers was also considered, but these too ambitious plans were left for the future :)

    I figured that the stove needed about 300 full bricks (or about 500 with halves, quarters and other parts). Standardly, in an hour and a half I was able to make about 20-25 bricks. Those. about 18-22 pm for tamping the clay into the mold and pressing the finished product onto a shelf for drying - and the complete set of products for assembling the furnace is ready!

    I used a fairly dense, hard clay, smoothed out all the folds-irregularities, cut the quarters and halves in parallel (and also estimated the need for them). Therefore, this process stretched out. Unit production is the most time-consuming.

    The Law of “Square - Cube”

    Having chosen a reduced scale of bricks, in practice I felt the law of the “square-cube”, which reads:
    If a physical object is increased in size while maintaining the constant density of the material from which it is made, its mass will increase in proportion to the coefficient of increase in the third degree, while its surface area will be squared by a scale factor.

    Example : A real standard brick has dimensions 250x120x65 mm and a mass of 3600 grams. The density of the brick is equal to 1846 kilograms per cubic meter.
    Reduce its size by about 6 times. We get the linear dimensions of 42x20x11 mm and a mass equal to 17 grams.

    Those. a change in linear dimensions in a ratio of 1: 6 led to a change in weight in a ratio of 1: 211. Anyone can repeat the experiment at home.

    Practical conclusions (in relation to my experiment) - the mass of the entire furnace model will be no more than 5-6 kg. Which is very convenient for construction, transfer and storage. Bricks of similar sizes are not yet miniature (tweezers and a magnifying glass are not needed), but they are no longer “cyclopical” either - dragging extra weights and allocating half a room for “construction” is not required. Everything is going quickly and conveniently on the table or window sill.


    Firing - until I touch. For masonry, the strength of raw brick is enough. Firing requires access to fire, stoves. In IT language, these works can be distinguished into a separate subsystem and investigated later. In the meantime, we believe that in the Firing () method there is a temporary "stub" that always returns "true".


    I started creating a furnace by studying the theoretical and practical experience of mankind. Everything has been worked out in detail on this topic for a long time - fuel is expensive and it is expensive to burn it (in all respects). Therefore, people came to a number of optimal designs that allow to get the maximum heat from a unit of firewood, coal, peat, etc.

    As a sample, I chose a typical PTO-2300 heating stove.

    Design parameters :
    • weight - 1260 kg
    • the area of ​​heat-transferring surfaces is 5.5 square meters.
    • convection system - bell-shaped
    • chimney - mounted
    • type of finish - flashing

    Functional parameters :
    Heating capacity (with firebox for firewood):
    • with a single firebox - 1400 W
    • with a double firebox - 2300 W
    Heating capacity (with firebox for anthracite):
    • with a single firebox - 1600 W
    • with a double firebox - 2500 W

    Consumption of materials :
    • ceramic brick - 210 pcs.
    • fireclay brick - 76 pcs.

    With regard to heating furnaces, the situation is as follows: it is worth distinguishing between a firebox (the place where combustion processes occur with the formation of heat) and a heat exchanger (places in which heat is removed from heated gases).

    A firebox, as a rule, is made of fireclay bricks (in my model it is white brick), and a heat exchanger (or a system of channels, an array of stoves that store heat) is made of red bricks. The need to use fireclay bricks is caused by high temperatures generated during combustion.

    Different types of fuel require a firebox of different sizes, shapes and designs. And different air supply. In the case of burning coal and brown coal, peat requires a smaller firebox and it is necessary to have a blower - air supply from below, through the grates.

    I designed the stove for wood heating, so I took the dimensions of the firebox more and chose the hearth type of burning wood. In our area, domestic stoves are not heated with coal and peat (they are simply not available) - they use exclusively firewood.

    The masonry itself is very simple. If you do not use a binder solution, but simply type the furnace construct in rows, of course. Brick to brick, brick to brick ... We're doing a model, not a real sample, right? This means that you can not worry about jointing. In addition, perhaps in the future you will want to burn these bricks or use them in another project.

    By the way, the stove people say that a properly designed furnace does not require a solution in order to keep all its elements together, in a single monolithic design. Those. joint repair is needed only to ensure tightness and protect people from the entry of combustion products into the living room.

    At the bottom of the stove I made trenches- small air ducts in communication with the room in the underflooding part, through which the air of the heated room circulates. Chants increase the heat transfer of the furnace and eliminate overheating of the floor on which the furnace is installed.


    Initially, I wanted to mill a furnace and a cleaning door from duralumin, and cut the gate valves from tin. Then he changed his mind and quickly assembled and glued these parts from cardboard. It’s much easier and faster to get in size and fit the look with this technology. We cover everything with glossy spray paint, wait for drying - we get the products we need.

    Grate or hearth furnace?

    Initially, in ancient times, all furnaces were built hearth. In the process of evolution, man improved the furnace by adding a grate to it (for burning various types of fuel). There are heated discussions about whether to build a furnace - grate or hearth.

    In the grate fire chambers, firewood is laid on the grate (grate). The grate, respectively, serves as the bottom of the furnace. Primary combustion air for fuel is supplied through the grate.

    In a hearth furnace, firewood is stacked on a hearth. He called the dead floor firebox. In the hearth furnace, primary air is supplied through the firebox door.

    I discovered a number of advantages of the hearth furnace (compared to the grate, when using firewood as fuel):

    • the cold core disappears from the stove (duct under the grate). The entire furnace array warms up more evenly
    • firewood burns almost completely, higher efficiency, we get more heat
    • less soot and ash
    • the bottom of the furnace is heated not only by flame but also by glowing coals
    • a low level of condensate in the chimney is provided, tar does not flow. No unburnt fuel particles enter the pipe.
    • combustion in this case occurs from top to bottom, the fuel burns more slowly, more evenly, because only the top layer burns, and not the entire mass (as in grate burning)

    3D design

    Before starting work, I made a complete model of the furnace in a three-dimensional modeling program. I use FreeCAD (but any other will do, of course). This made it possible to see the upcoming “scope of work”, to study the nuances of masonry, to imagine the complexity of individual operations and to visualize the desired result. And, of course, I really liked the 3D design process itself.

    By time: it took four to five evenings to create a model of the furnace (on average, one and a half to two hours of operation). And this is taking into account the development of virtual masonry technology. The second time, I think I did it faster. In comparison, I spent ten times more time on the actual work itself. There are advantages of three-dimensional modeling and design.

    If there is no way to realize the idea live - you can make it virtually. The brain doesn’t care if it works with an image or its real embodiment. Pleasure (endorphins) we get almost the same.


    In life, there is always a place for a dream, the embodiment of your unique ideas and extraordinary projects. Live a full life, do not be afraid to let your imagination fly and follow it.

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