Bubble Lift Mechanism
I'm using a car wiper motor for moving the bubble up and down. These are available cheap on the secondary surplus market. I guess after a certain automobile model goes out of production, the surplus electronics dealers scoop up a bunch of parts. What would have cost you over $100 while the car was in production can be gotten for $20 now.
I created a motor mount just below the collar. I mounted a cam on the shaft which has an offset center. When rotated it raises and lowers a PVC pipe that is supporting the bubble. I filed a small detent on the edge of the round cam. A micro switch with its actuator riding along the side of the cam detects when the cam is at the bottom, this way I can monitor the position of the cam and bring it back to the "home" down position whenever I need to.
Here's another picture from a different angle. It’s a little touch to see as I used clear acrylic for the mounting brackets as well as the cam. Using a cam really is one of the easier ways to convert rotational motion into linear motion and still have precise control over the full range. I wonder if immediately after they invented the wheel they next had to invented a way of transferring the circular motion back to linear motion.