Hi Dave,
It's is funny how this sort of thing happens.... Believe it or not I am in the process of building a similar sort of design. I am using a 'coil' drive system which in essence is a form of worm drive. The design uses intermeshing rotors set at 25 degrees coming off a set of drive wheels. These drive drive wheels, powered by the coil, utilise 10 bearing blocks set at 36 degree intervals therefore giving me a 10:1 reduction for my Subaru EJ22 engine.
The beauty of the design is that it does not require a 'gear box' and its associated weight. It accounts for reduction, horizontal to vertical drive and allows the drive wheels and masts to be angled as required. And I have found that it is releatively simple to build.
There is a sprag clutch in the centre of each drive wheel that the mast (shaft) goes through and accounts for auto if/when the engine stops. Synchronisation is provided by two bevel gears at the bottom of each mast (shaft) that are in constant contact.
Yaw control is by an electro-magnetic brake on each mast that provides for torque loading. A 'crossover' switch is used when the collective is at a set position to swap the torque loading (which brake to apply) between the masts during low power/auto.
I have CAD drawings etc if your interested...... In fact I got alot of info regarding intermeshing designs off your web page, but never saw this little tid bit.
Cheers