ORIGINAL: Chevelle
Just a thought but I would imagine that having true working counter-rotating props isn't necessary for power. Have you thought about just having the second prop just spin from the prop wash from the first? The reverse pitch will make it spin in the opposite direction.
I just happen to be building a model of an aircraft with counter rotating propellors and was wondering what others thought of Chevelle's idea above. My intention was to simply have the counter rotaters for static and fly with a single prop but the idea of running a dummy prop behind has me intrigued. What are the drawbacks if any?