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BrickStove with container: History of the development of the BrickStove
News items on the BrickStove in historical perspective
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History of the development of the BrickStove
News items on the BrickStove in historical perspective

Wood burning stove build from stones
Saturday November 9th, 2002
Together with Hans Baarslag and his two companions Johan and Zuhair, we made the first setup of the new design for a stove as described in the website under BrickStove. We experimented in Hans new workshop, a former cow shed with no heating.
This is what we are heading for:

  • The stove will have a table like model. It rest on a metal frame 30 cm above the ground and is about 1 meter high.
  • The stove is constructed out of concrete paving stones (60x40x6cm) for bottom and top. In between bottom and top two walls are masoned from ordinary bricks with mortar. This mortar is just a 1:1 mix from clay and sand. Fire-resistant concrete tiles for lining are only used where the wood is burning.
  • Air is pre-heated before it reaches the fire. To attain a very high burning temperature the actual fire place is small. It is expected the fuel will be consumed at a slow pace. This is in contrast with normal wood burning stone stove that burn their fuel fast.
  • The hot air on its way to the chimney is guided outside of the brick walls, behind metal sheets, that clamp in between the top and bottom. These metal sheets can be cut from a flattened oil drum.
  • Wood as fuel is fed into the fire from a pipe-like container positioned above the fire. The container is closed at the top.

  • Masoning a wood stove out of bricks
    Wednesday, November 13th, 2002

    Today we started bricklaying for the wood stove in the workshop of Hans Baarslag and his colleagues Johan and Zuhair. On a frame, welded out of steel tubes, four concrete pavement tiles (size 60 cm x 40 cm) are placed. Five layers of bricks form a wall. On the inside horizontal channels will guide the hot air from the actual fire hearth to the outside of the wall.
    Metal sheet panels placed outside this wall further guide the smoke to the chimney, while transferring its heat to the workshop. The picture shows the way in which the roofs of the channels are made out of two bricks resting against each other.
    We used mortar made out of 1 part dry sand mixed with 1 part powdered clay. When dry, this is easy to mix, then water is added. We will experiment with a mixture of 1 part powdered clay with two parts dry sand. A 1 to 1 mixture is rather soft and limits the number of layers that can be laid to three to prevent sagging.

    Design, hands on
    Thursday, November 28th, 2002

    I tried hard, but could not work out a work out in advance a proper set-up for the core of the stove, the firebox that should fulfill the following demands:

  • The channels in the stove had to fit inside the two walls erected last week.
  • Parts for firebox and channels should be stacked on top of- or next to each other and stay in place without plaster.
  • Parts should take compression loads only and no bending force, specially when in contact with intense heat. When cracks occur over time, this will prevent displacements of parts.
    Today I let the actual situation be my guide. Together with Hans and Zuhair we took only the step that was evidently appropriate, before considering the next.

    Zuhair removed top and bottom of a 200 liter oil drum and cut open and flattened the side. From this sheet metal he shaped the duct, that will be fastened between the top and bottom concrete slabs, outside of the wall. (see picture)
    I regretted not to have available an ax or cutlass. Zuhair had to work with good quality tools such as an electrical hand fret saw and a table sheet cutter to cut the sheet metal parts.
    From experience I know that the seemingly more primitive working with an ax for cutting and a dull cutlass for folding works by far faster and more accurate. Just an underground of dirt works best. I still have to describe these methods in this website.

    Hans and myself worked on composing the setup for channels and fire box inside the brick walls.

  • Directly over the concrete slabs a metal sheet rest on strips of bricks to facilitate heat exchange between the cold inlet air and the hot gas from the fire box.
  • The firebox is wide at the top and narrow at the bottom. This is done by placing two tiles slanted against the outside walls. The space behind the slanted tiles functions as the channel to guide preheated air to the opposite side, where this air can enter between the grates of the fire box.
  • As grates of the fire box function four tiles placed between the two slanted outward tiles. The proper distance between the tiles came from placing small stone wedges between the tiles. (see picture)

    We expect it to function as follows: Fuel wood slides down from the container to the top of the grates, that is the top edge of the tiles. Burning parts falling off, slide down while burning to a smaller size. Small parts falling through, burn to ashes on a plate positioned under the fire box.

  • Hot gas from the fire box moves horizontal through a channel, then up to a channel on top of the first. Then is can escape side ways into the meal ducts as Zuhair has been working on. From there flows out to the chimney (shown near the window).

    Hans indicates with the empty container for wood fuel where it will later be positioned (see picture)
    Building blocks with a special shape as used this time will later be cast from concrete or heat resistant cement. For this experiment Hans cut them to size with a fast running diamond disk, a very dusty job.

    To design hands on, with clear preset conditions but without detailed plans, works well to overcome a deadlock in design. As the problems are clearly visible for all involved, ideas come in at the right time. This was how it went during most of this job. Only at the very beginning misunderstanding and distrust in the good outcome hampered effective cooperation.

  • Forced draft first tryout or warming up the winter with a fan
    Sunday, December 22th, 2002

    Some news this week also on the brick stove. Hans Baarslag build a fan in a box. He and I connected this box to the chimney pipe and fitted it into a window sill. We were too cold and impatient to properly seal the stove with mud mortar. Thus we lightened a fire in the stove and switched on the fan. There was no smoke pouring out of the many openings, like the first time we put fire to it. But soon there was the welcome warming of the metal covers on the outside of the stove. Half an hour later it felt good to sit on top of the stove. The temperature of the chimney pipe was only luke warm.
    Hans and I decided to forget about making a chimney that would produce enough draft through the stove and further develop forced draft by a fan. This fan could run on electricity, but it also could be propelled by the heat of the stove. A simplified Stirling engine would be ideal for this job.

    Forking in ventilating the chimney-less wood stove
    Friday, April 25th, 2003

    Forking is the expression for a split in approach, a new way taken up next to the research that goes along according to a previous plan.
    Bram de Vries, one of the people I recently met through the contact with LHUMP thought different about a method to create the draft of air through the stove.
    Demotech proposed the use of a Stirling engine. Such a machine could have a very low efficiency, as heat was plenty available in a stove, while the energy needed to drive the ventilator was but a little.

    However Bram asked himself the question how to reach the same effect with even less moving parts. Today he came over to our workshop to discuss and demonstrate his ideas.
    He started experimenting with a tin can functioning as a vessel to heat up air. Over this vessel a rubber membrane is attached with an air valve in the middle. This valve should switch at reaching the top and the bottom of its stroke, thus creating a draft by sucking air in and pushing air out.
    Bram realizes his forking concentrates on a mechanical train of thoughts. Next step is to discuss it with people who can make a proper calculation, as the expansion of air by heat can be properly calculated. To inspire these people he plans to make in his kitchen at home a new set up, clarifying his idea better. Such a contraption could even shown a first sign of life!

    Games with heat and air
    Octobre 12th, 2003

    Mail contact with Sasha Mrkailo, Serbia brought me to this link:
    First of all it shows the feasability of the idea of forced draft through the oven, as tests show. This encourages, as Demotech explores this principle in experimenting with the Brick Stove.
    Second it shows how helpfull it is when information exchange really centers on the issue at stake. It saves everybody a lot of valuable time.
    The picture indicates how the draft through this small stove results in gassifying wood and burning this gas in the top part of this stove. It looks like a very smart game with heat and air. How it works is explained in this article.

    BrickStove testing,
    octobre 27th, 2003
    At the workshop of Hans Baarslag in Wierden, the BrickStove waited for a test. New to be tested were three items:
  • the lining of the fire box made from thin stainless steel sheet (0,5 mm),
  • the new set up of the conical funnel, the 'catch' where the wood from the container gets stuck, while sliding into the fire box,
  • the ash tray, also folded from sheet metal, that takes part in guiding the burning gassified wood into the "flame tunnel".
    Thanks to the link we got from Sasha I now understand better the two phases of wood burning: first the gasification of the wood, followed by the burning of the gas. Air (oxygen) for such secondary burning is still available in the gas mix or streams in through a second opening.
    Actually these two phases could well be observed through a glass window: wood, while it was burning and smoking remained stuck into the catch. From time to time charred peaces fell off, lining the ash tray with burning charcoal. Blue and reddish gas flames where sucked into the flame tunnel. (see top picture)
    The steel sheet lining for the bricks, the shape of the 'catch', the ash tray and the entrance to the flame tunnel, all seemed to function as foreseen. However not so the in-flow of air.

    So we reconsidered the idea of pre-heating air, similar as is done in steel furnaces. As the BrickStove is build now, cold air from outside is pre-heated when it flows along a metal separation in the flame channel. It then flows under the ash tray and enters the fire at the front, the place where the window is positioned.
    This functions only partly. Because the fuel (wood) container still has a very rough fit in the top of the BrickStove, a part of the air sucked in by the ventilator, leaks in through this bad fit.

    Joel Fransen, Demotech's new intern from the Design Academy in Eindhoven, suggested to make this accidental air leak the one and only entrance for fresh air.
    This is a nice kind of break-through idea, upsetting the present basic set up, but giving another simplistic layout in return. With Hans I planned to build a second stove in this way (see rough scheme of the new setup).

    1. Fuel container, filled with anything solid that will burn.
    2. The conical funnel, the 'catch' where the wood from the container gets stuck, while sliding into the fire box.
    3. Flame tunnel and interior space where the burning gasses transfer their heat to the stone exterior.
    4. Exhaust to ventilator. Forced draft sucks in the air at the fuel container, blows it outside.
    5. Brick exterior heats up while the fuel container feeds the fire. Its outside radiates its heat outwards for a long period after the fire is extinguished.
    6. Top of metal sheet can be removed for inspection and repair.

  • BrickStove with container: History of the development of the BrickStove
    News items on the BrickStove in historical perspective
    < Previous | 1 | 2 | 3 | 4 | Next >