X8 and Contra Rotating Efficiency - A simple study

[Bartman]

I found this useful....Dont know why no one bothered to test and post before...so simple!

interesting but is it really relevant? the bottom prop is freewheeling due to the airflow from the top propeller so what is the conclusion from the test?

 

[eskil23]

Also, the power consumed by the windmilling prop is lost because it is (must be?) contra-rotating. A windmilling corotating propeller would actually add thrust compared to the single motor.

Now I've had the time to look it up in my reference literature. It is called a Vane Wheel. A free-wheeling, corotating propeller with larger diameter and larger pitch that is powerd by the downstream of the main propeller will add to the efficiency by transforming the rotational energy of the airstream to thrust.

 

[DucktileMedia]

One experiment i never got around to would be to make an adjustable motor separation assembly. This way you could separate the vertical motor distances as you read the output. I think this single handedly would have the biggest effect on performance and would need to be fine tuned for every setup. As everything in life has a resonating frequency you would need to dial it in for each individual setup. Somehow or other when NASA develops a coax it is more efficient. So clearly there is a way to make that lower prop "bite" into the dirty flow of air coming from above in a way that somehow benefits overall efficiency. I think making a cowling is a must as well to get max efficiency. maybe someone will one day come up with a way to economically manufacture these as they will not only protect things from hitting props but greatly add flight time. But what do I know. It has always been an interesting aspect of multirotors.