Contra-rotating propellers are nothing new - they've been around for decades. Most require a gear box between engine and propellers using two shafts (typically one inside the other) rotating in opposite directions.
This take uses a single feed shaft. Rotation is divided between clockwise and counter-clockwise in the hub between the two propeller planes. The gear system is a modified planetary transmission -- very simple. It uses spherical geometry rather than traditions cylindrical-type gears.
I have coupled it to an O.S. Engines LA-40 glow engine (0.40 C.I.) to show it can be used by RC aircraft.
I know how to make it variable pitch, but won't do that until I have finished prototyping the fixed-pitch version. I'm hoping to control pitch using a single SG-90 servo.
I am tying to make as much of it as possible out of printed parts. I will shortly put the models of all the parts up for download at www.ranachy.org
I'd really like to make (or help someone make) a quad-rotor that utilized contra-rotation using electric motors or glow-engines.
I modeled it in SolidWorks -- including the awesome animation linked on this page.