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Oztrain Kiln: Firebox ConstructionSideStoke home | Oztrain home | Construction home |
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The Bourry downdraft firebox is discussed here, and the floor of this one is shown here.
It has some advantages compared to a simple anagama style
cross-draft firebox: easier to stoke, easier to control the ember bed,
and if you subscribe to a theory of Steve Harrison's, provides more fly
ash because the burning wood products have to drop through the flame
path on the way to the ember bed. On the other hand, the wood has to be
cut to a restricted range of lengths in order to rest on the hobs. Too
short and they fall down onto the ember bed, too long and they will not
fit into the fire box at all. |
| In the image
above the steel work for the Bourry box has been partially and temporarily set up,
arch bricks for the throat arch have been assembled, and a piece
of weldmesh to be used in the arch formation has been put into
position where the arch will be located. The final position of the arch is higher than shown in this image. In the final
configuration of the steelwork the throat arch will have to be braced at each end to prevent it collapsing. |
| Bracing
to constrain the arch has been added and the arch propped up into
positon,using bricks and bits of wood under the weldmesh strip. The
shape of the skewbacks needed to support the arch was determined
at this stage. Final arch position is higher than shown here. |
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| Three
skewback bricks were needed on each side but with just one on each side
the arch was stable enough to lock into position without mortar. Final arch position is higher than shown here. |
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The skewbacks were cut from ordinary firebricks using a masonry cutting disk in a 9inch circular saw. Final arch position is higher than shown here. |
| The walls of the firebox have been built up to the final height, with the hobs constructed to form ledges to support the wood. |  |
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1. Primary air holes 2. Secondary air holes 3. Lower door 4. Mousehole |