You might do a search on Google for an Americn experimental military aircraft nicknamed Pogo (can't remember the official designation, TGIF). VTOL, mid-50s. If I remember correctly The project was shortlived, as were the aircraft.
Isn't there a Russian long-range bomber, swept wing ("Bear"?) with counter-rotating props?
Good luck. I'm not an aerodynamicist but it just doesn't seem logical to whack away at the air one way and then, 30cm back, whack away in the other direction. And the gearing must be diabolical.