The twin-rotor Chinook helicopter is a remarkable design. If anyone suggested having two sets of counter-rotating interleaved rotor blades they might well be criticised for optimism bordering on naivete…my speciality, in fact.
Today’s invention is a Chinook upgrade in which each rotor blade engages its outer end with the distal rotor hub, driving that hub’s rotors around until it slows enough so that that end then becomes the inner end of the blade rotating about the distal hub.
This stresses each blade more evenly and lessens the overall sweep of the blades as shown in the diagram -in which the helicopter is flying up the page. The single blade shown swaps from hub to hub, providing drive for one rotor from the other without any need for a drive shaft (difficult, but not impossible to achieve).