Below is a peak at the internal mechanism before the top of the vessel gets attached. The vessel tube is a 1-1/2" ABS pipe. The dome is made from wood. The level gauge is attached through the side. As part of it there is a 1/4" dowel drilled out with a 3/32" hole through the middle. The pointer on the gauge is soldered to the end of a 1/16" brass rod that slides through the centre of the dowel. The dowel is glued into the hole and reinforced by the plywood brace shown inside. A brass lever arm is soldered onto the brass rod on the inside. It is aligned so when the pointer is vertical, the arm is horizontal. This allows the right orientation for the best maximum motion. The 1/8" dowel inside keeps the shaft from over rotating until it gets hooked up permanently.
In case you haven't guessed the actuating rod goes down through the bottom of the vessel. You can see the wire attachment in between the dowel and the brass rod in the photo. Now just put the top on!
Automata is a creative blend of my life interests , engineering, art and woodworking.