H8 frame Pixhawk 4

Hi, wonder if any one can help on this.
I have designed and built a very large H octo, all works but in Ardupilot only has a quad H frame. does it use two motors on the same arm as one but different rotations to each other or is all 8 controlled separately. I have looked at the X octo but having issues with two motors on the same arm slowing down after 50% throttle and some left and right movements. restart the octo and all is good with the motors and then it does it again. I know its not the ESC or the motors
I think that it will support 8 motors but the confusing part is, the numbing of all 8 motors and rotation of all 8.
I have tested the motors and ESC on a different flight controller and do not get the same motor slowdown, but I do need to use the pixhawk on this project.
Please any help on this would let my hair grow back again lol.

Update to ArduCopter 4.0.4 and post some .bin logs

HI, thank you for getting back to me.
just done another tes,t recal every thing.
in servos i see all 8 motors, then i throttle up to 50%… move the sticks to full ali and elevator back to centre all seems ok
then i move the rudder and things get interesting, the same two motors slow down to about 1/3 speed and there is another two that start revving up slowly, they all do not center them selves. thottal off and start again all is as it should be until i repeat the movements.
i left it running for about 5 mins with out touching the sticks and they all stayed in the mid range ish.
i will do as you said. and see if there is a difference.
i did also changed the X octo to H same this happens.
not sure how to do .BIN logs

If the copter is not flying, the motors behave erratically.

Hi, i cant let this go free flight as the weight is 14Kgs, so all I can do at the moment is do a strapdown test. its just the rudder stick that is doing this, all eight motors are reving up or down. all other sick commands are ok.
what i need to know is, is the H frame configuration a quad with eight motors each pair operating as one, or each one of the motors operating independently from erah other.
the location position of the props and direction of rotation.
its not clear on any thing i have looked at so far.
i am using ardupilot 4.0.4

Hey! You don’t need H8 configuration for coaxial setup with all motors controlled independently. The X8 config that’s on Ardupilot wiki should just fine since the torque yaw doesn’t create any torsion in frame like quad H-frame.
Just use X8 config and you should be good.

HI I had that on yesterday, but still had the rudder problem motors doing this thing, as I said it seems to be just the rudder stick when i move it.
I will reflash it back to X8 again.
Disarm and then arm increase the throttle, its good until i move the rudder stick then it starts.
I am looking at how to download the logs now.

Share a video with log file.

Again, regardless of parameters or settings, a strapped down copter will move the motors erratically. Period.

Hi, just reflashed the firmware and re cal every thing.
set it to X8 conf. am i looking to hard at this, its just worrying that if i let it fly it will go nuts, a year in design and tones of cash on it for it to smash its self in seconds.
props off and the same happens.
inc the radio settings.
motors spin up ok.
until the rudder input.
i will put up a vid soon

yes i would expect the motors to not behave as the should, some differences, but this is just so bad. some motors go into 90% and some are where the should be, others are just over 10 to 15% idle, its not instant but a creep down and up. with the throt stick at zero then increase it rights its self until the rudder it all goes to put again.

being a total Deerr… here what logs are needed and where are they.I have never used Ardupilot as I am a usualy a manual flyer.

Lots of people have been in your situation before you. Tried to validate motor movement on a straped down copter. Some of them come to this forum and ask the same questions as you do. We answer it the same way, motors do not operate correctly when strapped down. Then they are very suspicious of our answer… Then they test it and it flies. Then they thank us… :slight_smile: :slight_smile:

This loop repeats itself every three months. You are just the September iteration of the same issue. Just search the forum, if you do not believe me.

That said, of course you should test as much as possible before taking off. But you should add props and tie the copter so that it can only move one centimeter of the ground… That will give you safer results than a fully static test.

We need .bin log files.

HI yes i do understand you, just being very safety minded here as it weighs 14Kgs
i will do that as soon as it stops raining here.

ok, would it be ok to test the pram in simulation mode?
if so HOW THE Hell do you do that, and what do i need. i have looked at the Arducopter side of the sim but cant work out what i need, looked at some google things on it at it just became more and more confusing.

The simulation won’t do anything for you in terms of hardware. You can watch the craft fly nicely around in the simulation but then if you connected the motors wrong (out of order) or the motor direction is wrong it will likely flip on take-off.

And the only useful thing you can do with the props off is run the Motor Test Function in Mission planner to confirm proper motor order and direction.But surely you have done this already. Perform all the mandatory calibrations, put the props on the right way and make a test flight. If you do tie it down things will go wrong if the tie downs are tensioned. The whole point being made here about this is the craft needs to be freely flying for the Control Loop to operate correctly.

HI yes i do understand all this, it will be bum twitchy time lol.
i have been through the set up so many times. i cant risk the thing getting out of control.

Hi, the tie down test was done with props on (and all on the the correct way, motor spin the correct way), as soon as the weather here is good i will go for it (still tethered tough.
i did also think that I would zero all settings and re install the the Ardupilot prog. start from fresh.

Im going to try a brand new un used pixhawk 4 , before i give up and let it free… see if the problem is the same on this.

What problem is that?

Ok did the swap out problem has changed to the front motors, I can say now it’s not the ESCs, motors or the flight controller. It is definitely software. If I move the flight controller the motors speed up, so once it’s stopping raining this week I will recal the compass and try again in open ground.