@DaOldMan- It does have an encoder, but I would need to upgrade the controller to one that accepts feedback, the pololu JRK. I don't think it would work well, its not absolute positioning but just counting pulses/quadrature. My system is fairly refined at this point but there is still some slippage from time to time between the motor wheel and the monitor disk. I'm on my 2nd type of sandpaper applied to the monitor disk (started off with some 1000 grit, I think I have 150 grit on there now. the motor has enough power to keep turning even if the monitor disc is completely stopped. One time it rubbed the tire right off the wheel. With the 1000 grit, even the weight of the monitor cables hanging off could cause it to slip. With the 150 grit traction was vastly improved but I still routed out channels in the monitor disk to have the cables exit through the center of rotation.
Bottom line, that encoder is better for measuring actual speed than actual position. I'm going to experiment with speed commands because, worst case, it hits at full speed, not a big deal, or if it slips and times out to the lower speed, it will just rotate slower until it hits the stops. Right now I'm just running at 50%, letting it hit, doesn't seem to be a big jarring of the monitor, and the braking holds it acceptably tight to the stops (100% braking set right now, it can be set from there to 100% coast).
Looks like you and DNA Dan have set a new standard for rotating LCD monitors.
Thought about rotating a CRT?
This is all DNA Dan's research and testing, I'm a follower on this one.
I guess I'm a post CRT guy, and by no means an arcade purist, so probably no arcade monitors for me. It is a more challenging engineering problem. I would look at the drum/roller/axle hardware from a junkyard clothes dryer if I had to do it.