Firebox Design for the Vertical Boiler

After lots of building and testing I’m finalising the firebox design for the small vertical boiler. The optimised distance between the top of the wick and the base of the boiler was 60mm. This was all measured on a test firebox and instrumented boiler.

hexagon made from sheet metal

My original thought was to machine the solid hexagonal bar and create a firebox. However, what a shame that most of this lovely hex block will be turned to swarf. There has to be another way.

So, a walk, a think and time to ponder.

How about folding the firebox up out of mild steel sheet? Some 0.7mm sheet had just arrived and felt about right.

I thought about a single wrap and then joining at one side, but I like the hexagonal shape and the idea of 3 seams. These seams could also form support posts.

Hence 3 panels of mild steel bent in the middle and with a 5mm wide edge. These are simple bends to make, especially as I could use the hexagonal steel bar as my guide.

I did have to finally form and pull the seams together with the hexagonal bar of steel in the centre. I used the engineers vice to pull each pair to a tight fit.

hexagonal steel firebox

I now have the shell of the firebox. It just needs an opening, air holes, a base and a top plate to support the boiler. The firebox design for the vertical boiler is in progress and looking good.

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