I have an engineering background, I'm an EE, but I know almost nothing about mechanics and that's why I'm writing here.
This is the challenge: how to control the rotation of multiple discs along the same axis? Assume you have a sliced cylinder. The ideal scenario would be to control every slice independently, but to make things easier I think it helps to consider that you can move them in a fixed number of combinations and on the same direction (e.g. a mechanism that enables to rotate the top and bottom cylinders at the same time and same direction - combination #1 - and the inner ones in the same way - combination #2 - but not as the same time as #1).
Any idea on how to accomplish this?
I though I could use something like a "key" along the axis/shaft/rod. By moving it up/down it would lock different discs/slices. Not sure if this is a good idea. One issue I can see with this one, is that the slices that weren't locked by the "key" could be rotating freely and I want them to be steady.