Since we are all making wild guesses as to what you actually want to achieve I thought I'd add my own version.

If you are simulating or writing a control system for a robot (it comes to much the same thing) then Robo should be a container for a collection of RoboParts derived objects. Robo probably isn't a RoboPart, but that depends a bit on what your end game is. If the Robo instance takes external instructions from a console then it may well benefit from deriving from RoboPart. If instead it is a self contained instance that manages the various RoboPart objects then it doesn't derive derive from RoboPart.

Maybe you'd like to tell us what you want to achieve and not how you think yo might best achieve it? Then we can help you get the class structure right to support your objective.