I have always wanted to make one of these and now I want to make some more. .DO NOT MAKE ASSUMPTIONS about the contents of cylinders and flammability and if the cylinder is full empty or part empty, check check and check use an expert who is not cocky about it. The cylinder chosen was an old and DEGASSED Carbon Dioxide cylinder, flammable contents present more danger as do oxygen cylinders (the oxygen can lower the ignition point of hydrocarbons to room temperature, be very careful and avoid completely if you are not experienced with dealing with the concepts involved). I heard a story about an air service navigator breathing oxygen who bit into a cheese sandwich and the margerine reacted with the oxygen.
And get your cylinder from a reputable source (see above).
It makes a wonderful noise and we are blessing it tonight.
USE safety equipment Goggles and a full mask, metal working gloves of appropriate strength, and a leather apron there are a lot of hot sparks and they can burn through jeans (I know).
The top can be chopped off and the bottom with an angle grinder with a quality metal cutting disk some of the cylinders can be quite thick so be prepared to be patient and don't apply too much pressure as the disk gets distorted and the cut can go off line and shatter the disk.
Once cut the edges are likely to be very sharp especially the "hole in the top which acts like a blade. I found a "flap wheel" worked really well and was quite controllable as they tend not to "snatch" at the metal as one works it, useful on internal surfaces when using an electric drill.
I stood my cylinder upside down and the ring seems to be unaffected.
I have yet to decide how to finish it, but for now I use an off cut of 6x2" timber as a stand.
Any suggestions welcomed.
as the shell pressing is uneven the noise does a nice oscillation (could be the cylindrical shape).