Brake disc has a step on the od to fit inside the caserole dish. It has has recess turned in it to take the cylinder liner. 4 bits of m12 threaded rod are welded to the gas bottle and pass through the wheel stud holes in the disc to bolt everything up tight. A spring presses on the bottom of the caserole dish to keep that in place.
Just a quick note to add to this thread as it's not worth starting my own.
I've recently been playing around with an ozzirit style burner. Am having some success utilising an oil control box from an old oil fired Rayburn. It needs a touch of simple modification for thicker oils but has the advantage of having very fine adjustment that isn't affected much by temperature changes. And most importantly for me, has built in safety mechanisms so if the fire goes out, it will stop filling once the set level is reached.
They are easy to come by around here but generally come attached to 1/2 ton of scrap that has to be removed at the same time.
Rather trickier to clean out though as you have to feed oil in by the bottom of the pan so can just lift the pan straight out.