@Paul_KD7HB Thanks, it makes sense to take that approach. I read through the following page, but I'm unable to decipher most of it.
The second diagram mentions a "planetary gear case" and the description of that can be found below the diagram. It refers to a first and second stage planetary gear section. I'm guessing that means there's a shift in gear ratios at that point, but I couldn't say for certain.
@TomGeorge The helicopter will not be able to fly. That's not my intention. It's just a display model with some bells and whistles to bring it to life through light, sound and motion.
Thinking along the lines of a 3-stage gear shift. Would it be possible to use 3 small dc motors and apply a gear ratio to each of them. 1 capable of the lowest RPM required and 1 capable of the highest RPM required. The third motor would bridge the gap between the other two. All three of them would be connected to the main rotor shaft, but only one of them would be supplied with power at any given time. I could cut power to the first motor and have the second take over and then cut power to the second and have the third take over.
I think one of the problems with this could be the fact that they are all connected to the main shaft at the same time. The gears for the motors that are not powered would still be turning which would generate some kind of energy in the coils of the unpowered motors? Again my lack of understanding doesn't help matters.
Could something like that work do you think?