X8 Coax Experts

[JLO]

To all X8 Coax setups experts
questions:

1 Are you using DJI x8 (Octo-rotor X) mixer as it is, Top props counter clock rotation, bottom prop clock rotation? or are you modifying this setup

2 Are you using same size props for top and bottom motors?

3 Do you know why in the advance motor mixer the boxes for the mixer numbers are in 0% instead of a value?

4 Has any one modify the numbers in the advance motor mixer? if yes could you share your numbers to have an idea

Thanks guys it would be great to expand our general knowledge about this

 

[Cheshirecat]

I run an X8 using the default DJI scheme all top = CCW all bottom = CW. It flies well as is.
I did try to setup an alternative custom mixer with my HerkulesIII as sugested by the designer but i had an issue with 2 of the motors failing to initialise on the bench so went back to the "if it aint broke" approach with the default setup.
I run 15x5 Props and have run it with 15X5 on top and 15X6 below and i beleive i saw a small improvement in climb/decsend (uncommanded) in horizontal flight (ie altitude hold) but then broke one of the 15X6 so been running all 15X5 since, not unhappy with it as is.

 

[Quinton]

There are people running the configuration as it the picture below.

There was a post earlier i a German forum about a person who tried out changing the bottom motors to try and even everything up a bit, and he ended up at around 93.
Would love to try this out in the future to see if it makes any difference, although I would prefer to have telemetry on each motor which I don't have, instead of relying on bench tests only.
This would really only deal with efficiency, and not address how well it flies, very interesting though if you had a proper setup to test the theory.

 

[Cheshirecat]

Thats the config and mixer setup that Andreas Baier recommends but for un identified reasons i could not get Motors 6 and 7 to initialise in the motor test utility on the WKM. put the Mixer back to defaults and all was well, would love to find out why?

 

[Quinton]

Thats the config and mixer setup that Andreas Baier recommends but for un identified reasons i could not get Motors 6 and 7 to initialise in the motor test utility on the WKM. put the Mixer back to defaults and all was well, would love to find out why?

I had no motors work in the motor test once with the WKM, but it was fine doing CSC so did not worry too much about the motor test.

 

[Cheshirecat]

CSC? What is that?

 

[Quinton]

CSC? What is that?

"Combination Stick Command" basically what you use to arm/disarm your motors.

 

[Cheshirecat]

Well of course it is:shame:

 

[JLO]

Some guys at the Freefly forum are using a mixer similar to this and like it a lot, also are you guys getting actual number in the boxes of the advance mixer menu?
Quinton where did you get the digits (100)

Mikrocopter FC mixer window had values of 64 and -64 across all of the mixer boxes as defaults, in recent months MK did a slight modification to the default values where for example in a octo mixer, motor #1 and motor #5 had no value on roll, and motor #3 and motor #7 had no value on Nick, when you look at it it makes sense

so the question is: base in the theory that a mixer in DJI or MK may work similar has any one experimented with DJI A2 or Wkm mixer values on a simetrical octo, hex or quad? what the values would look like if we copy the MK way, and would this help the overall flight performance stability​

There are people running the configuration as it the picture below.

There was a post earlier i a German forum about a person who tried out changing the bottom motors to try and even everything up a bit, and he ended up at around 93.
Would love to try this out in the future to see if it makes any difference, although I would prefer to have telemetry on each motor which I don't have, instead of relying on bench tests only.
This would really only deal with efficiency, and not address how well it flies, very interesting though if you had a proper setup to test the theory.

 

[Cameraj]

X8 gain and setup,

What gains have you found with the x8 and wkm? I tried the default and got some crazy side to side action, I have also noticed I'm getting some white flashing lights, I'm run 6s tmotor 4014 with 16in prop wkm on a x8, any help would be great

 

[Cheshirecat]

What gains have you found with the x8 and wkm? I tried the default and got some crazy side to side action, I have also noticed I'm getting some white flashing lights, I'm run 6s tmotor 4014 with 16in prop wkm on a x8, any help would be great

I Have all my gains at Defaults (all at 100%) and have the basic gains linked to a pot on my TX, i usually fly with them set around 86% unless it is windy and i might up them to around 120% and happy with the performance.
I have also had them set at:
Basic - Pitch = 160 Roll = 160 Yaw = 150% Vertical = 150% and Attitude Pitch = 70% and Roll = 70% also flew well but found i was dialing them back anyway so went back to defaults when i swapped out a BAD IMU V2.
If you are getting flashing white maybe there are excessive vibrations getting to the IMU. have you checked motor and prop balance? or the IMU isolation on its mount.
I upgraded my IMU V1 to IMU V2 and started getting wild oscillations in the hover (worse with a full load) and landing became difficult because the X8 would suddenly jerk sideways just as i went touch down, after 2 tipovers and 2 broken props and a lot of gain adjustments without any improvement i went back to the V1 IMU and everything dropped back into place, i have it down as a bad IMU V2 which now lives in the back of a cupboard.

 

[JLO]

Well I must say Im liking the X configuration a lot on the gains its kind of hit and mist, what I did is put the roll and nick gains on 1 a knob and the attitude gains on the 2nd knob of my futaba radio i found out "i think" (need more test to verify more firmly this) that in calm wind flight I had to lower the roll and nick gains and on a windy flight I had to increment the gains, also on a forward flight I notice that I was loosing altitude so I also increase the attitude gain I guess it all dependes on the crafts Auw and how all of its main flight components play within in flight for sure more specific test flights are needed to understand and get this right