### Y6 / X8 Thrust efficiency test

Hi,

Almost 1 year ago I started a topic on the diydrons forum in wich I asked on how much efficiency loss I will have on converting my quad to an X8. Almost no reaction to my question. Nobody could give some figures wich I could use for my calculations. The only helpfull answer I got was from somebody who said that the efficiency loss depends on prop size and distance between the props.

Time has past, other projects are closed so I'm starting with the build of a Y6 multirotor. And the first thing before building the frame is a thrust test of 2 motors in sequence. Result is a 10% efficiency loss. See full graph and info on my blog at http://wipo-y6copter.blogspot.be/

This figurs can by handy for everyone who is building Y6/X8 copters. Currently I'm building the frame, but I will try to post more efficiency loss tests for other prop sizes asap.

• @koen.hufkens: I compared a hexa and y6 model full carbon and the weight loss for my Y6 model is zero. Because  a Y6 needs bigger/higher landing gear, wich increases the weight. A normal hexa can be equiped with no landing gear (just some foam arround the arms).

• Ok, looks like it's my turn to be the dumb ass asking the stupid question...

This means that you get 90% more thrust with two motors than with one motor? So - theoretically - with all other things being equal:

1 x motor @ 100% = 2kg thrust
2 x motor @ 100% = 3.6kg thrust

•  @Randy: I tested the thrust with a scale but not mounted on the copter because the frame isn't ready yet. The distance between the props on my Y6 copter will be less then 9 inch. So when I got the time I'll test that also :)

• the best way to reduce efficiency loos is to have the lower prop be smaller and higher pitch or angle of attack than the above offering both power and stability

• @Matthew Schroyer: the loss of 10% efficiency is acceptable in my project. I look at weight/thrust ratio and flighttime.

@John C.: I have some EPP 1045 that I can test and I ordered 12x45 slowfly props as well. result will be posted asap on my blog

@RoboCopter: Thx for the info, as soon as I got more props and the time I'll perform a test on your configuration.

• What would be the effect of the side-by-side distance on thrust efficiency?

• Great! Some folks here recommend using different prop size on top and bottom. I.e. 3dr coaxial frames use 10 inchs props on top, 11 inchs props on bottom. I assume they made their tests to get to that configuration...Woul'd be great to see the graphs in that configuration

• This is a dry test (motors on a bench) no? I wonder how much efficiency you gain from the lower weight of a Y vs standard hexa system. This would provide you with a true final answer. You might gain more form the loss in weight in parts than what you lose in motor efficiency. Any clues on how this would pan out?

• would be really interesting to see efficiency number change with bigger props underneath.. :)

• Hi

I am also building an X8 now. I have been wondering about the efficiency of coaxial arranement of the motors but have not been able to do any tests. I have different motors on top and bottom and also different props. Have you tested this with lower RPM motor on top than bottom? And also the effect of having having smaller propellers underneath with higher pitch. This is the arrangement I am going for and I am hoping this increase the efficiency.