Building the theatre scale fire tornado
This was the main request, but it also had to be safe, robust and store in a resonable volume. The mesh also wants a decent grip on the air, so I used an expanded aluminium mesh on an aluminium frame.
As it made sense (and partly because I have recently bought myself a TIG welder), this was to a large extent a welding project. I wanted to make the mesh look as uniform as possible on the outside so the frame is internal, which also means the mesh is better supported from minor impacts than an external frame.
The second piece of welding I did with stainless steel was pretty respectable (the first was rather less so... and required silicone sealent to be waterproof, but I bought 2 trays so all was well.)
The tube on its own was 2.5m tall, and my workshop is about 2.6m tall, so it was all a little tight. Assembly let alone testing of the full demo had to happen outside. Luckily the weather smiled on us, and Cambridge is pretty dry.
The mesh was wickedly sharp, especially where we had had to cut it. Luckily physics came to the rescue. An arc wants to start at a sharp point because the electric field is strongest there (this is normally a big problem with all kinds of arc welding, however in this case it was to my advantage. I ran the tig welder on a low amerperage along the edge of the mesh, the arc preferentially melted the sharpest parts, surface tension pulled the molted metal into nice blobs. Job done.
I painted the outside of the tube black to improve visibility inside under lights, which used rather more paint than I was expecting - it turns out the surface area of the tube is large, and you have to paint it both angleing up and down or the expanded mesh shades itself from the paint. (It looked great until I turned the tube over). 7 cans of spray paint later it looked pretty good.
It took a while to build, but who wouldn't smile when you have a 10 foot column of flame in your garden.. not sure what the neighbours thought...