X8 vs. flat octo redundancy comparison.

[jes1111]

That is the old story, people building flat octos claim that they are more efficient (compared to X8), and people (like me) building X8 claim, that the loss in efficiency can be covered by weight reduction.
I can build a frame for a 5kg (AUW) X8 with 150gr (14" props) , I am afraid, no flat octo frame with 14" props less than 500-700 gr is possible (with comparable stiffness). If you cannot save weight at the wiring when switching from an flat to an X8, there is something wrong.

Here an X8 with 60 min flighttime:
....
This copter has 14" props, and the copter has only 1,35kg possibly somebody can share the weight of a flat octo with 14" props for comparison ...

best regards
Ferdinand

P.S. I already thought, that the times of 10-12min copter has long gone ...

Sorry if you've explained this already - what prop pitch do you use top and bottom?

 

[FerdinandK]

@jes1111
I use the same on top and bottom,

... let the FC handle it ...

@Stacky
This (1,35kg) copter can carry 2kg payload so 1,35kg copter+ 1,65kg battery + 2kg payload gives 5kg AUW and 30min flightime

best regards
Ferdinand

 

[Stacky]

@jes1111
I use the same on top and bottom,

... let the FC handle it ...

@Stacky
This (1,35kg) copter can carry 2kg payload so 1,35kg copter+ 1,65kg battery + 2kg payload gives 5kg AUW and 30min flightime

best regards
Ferdinand

Im going to have to go look at everything again. I have watched over the last year or so your videos and length of flights you get.

 

[ary]

...let the FC handle it...
do you means you are using WKM custom motor mixer?
Would you share your custom motor mixer set up?
thx

@jes1111
I use the same on top and bottom,

... let the FC handle it ...

@Stacky
This (1,35kg) copter can carry 2kg payload so 1,35kg copter+ 1,65kg battery + 2kg payload gives 5kg AUW and 30min flightime

best regards
Ferdinand

 

[FerdinandK]

I am using the standard motor mixer, but I use CW and CCW mixed on top and bottom.

best regards
Ferdinand

 

[questech]

Im going to have to go look at everything again. I have watched over the last year or so your videos and length of flights you get.

So if each motor on each arm is rotating in opposite directions, how do you control yaw?

Does the FC know how to handle that?

I thought that you would have each motor on each arm rotating in the same direction in which case controlling yaw would be the same as with a fat setup.

I guess all the FC has to do though is slow down/speed up the top or bottom motor on the 2 opposing arms to achieve the yaw result.

I'm still deciding whether to go coaxile or flat for my current build??

AM

 

[FerdinandK]

On a octo (X8 or flat) there are 4 propeller CW turning, and 4CCW if the 4CW turn faster, the 4CCW turn slower, the copter turns CCW, if the 4CCW turn faster, the 4CW slower the copter turn CW, that is how YAW works, this has nothing to do with koax or not.

lg Ferdl

 

[questech]

On a octo (X8 or flat) there are 4 propeller CW turning, and 4CCW if the 4CW turn faster, the 4CCW turn slower, the copter turns CCW, if the 4CCW turn faster, the 4CW slower the copter turn CW, that is how YAW works, this has nothing to do with koax or not.

lg Ferdl

Thanks for the reply!

I understand that, what I don't know is how the X8, in particular, works to control yaw.

If the 2 motors on each arem had opposing rotation and were at the same RPM, all things being equal, they would cancel each other out from a torque standpoint. So initially I thought that you either had both motors on each arm rotating the same way (the props configured so that the thrust was vectored downward for both motors) or that the FC would change the RPM of the upper and lower independently, which I assume must be the case, especially after reading your reply.

Building an X8 has a lot of attractive aspects to it, but I read that there is an efficiency issue, which I need to explore further.

Thanks Again!

Anthony