I'm interested in how CR props work! On a mechanical level I can visualise some sort of planetary gear lash-up to effect reverse rotation off the crankshaft; but I am stumped by the thought of the 2nd prop (ie the one nearest the engine) taking bites out of an airflow disturbed by the 1st prop which bites into "clean" air!
I'm interested by it as well. It would appear empirically to be a bad choice since its so uncommon (both in propellers and helo rotors) but I'd be interested in knowing what advantages it does present and how bad/interesting the aerodynamics are. I wonder if a modern propeller could replace the CR deals on the Bear and perform similarly, and if not, why not.
Re: the noise of the Bear, I've never heard one but I've often read of that phenom. I've wondered if it has much to do with the contra-rotating design or just really high tip speeds.
why does the BAE 146 have 4 engines and the 777 get away with 2?
I can't answer any of your questions, but the answer to this one is rehashed weekly in this forum and a simple search out to turn up all sorts of (valid) reasons for the trend toward fewer engines when feasible.