I am building a helicopter cake that will have a very slowly spinning rotor blade.......what size hobby motor do i buy to make the 2 blade rotor spin very slow....maybe light balsa wood two blades 2 foot each.....

thinking a small plasic tube glued to the motor up thru the cake and hooked on to the rotors

what size motor and any switch to make it faster and slower

 

120 volt AC or 9-12 volt DC?

is hand-helping it start spinning an option or do you want it to start spinning on its own when the switch is thrown?

would stiff cardboard be a possibility?

 

You will probably want something hooked up to a gear box, I've seen decorative small Christmas trees like this, that turn slowly to emit different colors of light. A hobby shop may sell something like this. If not too heavy, a spring wind up, like those found in a music box. My grandson has a toy GI Joe Helicopter with a slowly rotating blades, that comes with sound effects, missle launchers, lights and etc. It's about a 20" rotor span. Maybe you could buy one on ebay, and gut the motor, sound effects card and speakers.

Good Luck