SQUARE OVEN home
 
Construction

This is the story of the first oven. It was a square oven with the inside corners camfered so the flame could whirl around the pan. The size was about 300*300*300 mm (12" * 12" * 12") The panels were made of 10 mm (1/2") material that looks like ordenary gypsum-wall panelling but it is a special heat resistant type used for the fireresistant making of metal constructionstructures in buildings. It has no cardboard on the sides. It can be found under the name of promatect. There are also other brands around.

The burner was inserted at the bottom. just beside the burner a little black tube can be seen. This tube gave extra air from a plain compressor. Without the extra air the burner had the tendency to quit because of a lack of air. It was a delicate balance between the extra air and gas suppletion.

The time to warm up took about 40 min. To shorten this time and to make the burner more stable I made a new burner. This was with no forced air involved. The instability was the same so I made another burner with forced air from a vacuumcleaner. (this is the same one as I used later in the big oven)

Problems

New problems were turning up. Each time the oven was used there formed little cracks on the places that were heated the most (in the middle of the sidewalls). It was not a big problem (yet) because other problems where bigger.

The second problem was the flame leaking/burning through the little gap in the paneljunction. See drawing C below. Each time it got a little worse.

The third and biggest problem was the delamination of the walls. I think it was because the metal screws got a little bigger when they are heated and they shrunk when the oven cooled down. (drawing A + B below)

Improvements

To make some improvements one could reinforce the edges with a light L-type stock metal profile (see drawing F above) there could be a few screws to secure the panels (drawing D above) but not to many. It would be better to use fireproof construction-kit.

To keep control of the cracks and leakage it would be a good idea to double the panelling. ( drawing E above) I think its better to use two panels than one panel twice the thickness.

To avoid nasty errors as shown by drawing G above, it is absolutely necessary to put the box on the floor and to make the lid removable (which was the bottom plate in my original design). This way you can make the burner hole in one of the sides of the box.

Important lesson learned

Because the oven collapsed partially during a session there was nearly an accident. The handle came off and I had a hard time to lift the oven with one handle. In the consternation I didn't pay attention to lift the box high enough and pulled it against the pan with molten metal.

At the time the "nearly accident" from drawing G occured, I was using the rvs cooking-pan from the top-image to melt the metal. It was relative stable due to its broad base. If I had used my later bilge-shaped graphite crucible at this time I am sure it would have tipped over and splashed the molten aluminium around and over my feet. Just the thought of the consequences makes me sick. I hope this story prevents someone to make the same error.