Motor unbalance

[hosein_gh (Hosein Ghanbari)]

hi everyone
i have problem with my CW motors they are working harder than CCW

what i’m done :
my frame is fully Quad
i replaced my ESCs
ESCs are calibrated
Propellers are OK
and my copter is not underpowerd

my config :
CUAV Pixhawk with AC 3.6.11
F450 Frame
T-motor Air Gear 350 with T9545 Propellers
Gens Ace 4S 5500 mAh Battery
EMAX BlHeli 25A OneShot125
copter weight is 1500g

any ideas how to fix this problem ?
is my CW propellers generating less thrust ?

and another thing is that T-motor Air 20A has 400Hz refresh rate and my current EMAX ESCs have 8KHZ could this make issue ?

[dkemxr (Dave)]

This happens when Yaw is commanded. It’s often seen on craft with round arms and the mounts are not aligned. On an F450 frame maybe it’s just those cheap plastic arms are twisted.

[hosein_gh (Hosein Ghanbari)]

@dkemxr my frame is manufactured by DJI and at the-least i don’t see any twist in my arms
and i forgot to say my copter is not tuned yet

[xbnr99 (Jfff)]

Hi @hosein_gh

Some ideas-

Have you checked the frame’s flatness with a level?
Since the battery is so heavy, have you checked the center of gravity while the battery is mounted?
Are you sure the battery is mounted securely and doesn’t shift during flight?
Does the vehicle hover in stabilize mode and is it stable?

[Anubis (Rick)]

Check RATE.YOut. If it’s not centered around 0 while the drone is in a stable hover, then you have a mechanical yaw bias. Usually this is caused by motors not being level.

[Harald (Harald Schmid)]

I see also that the trust with the ccw props is different than with the cw props with the air gear props. Have the same issue. Test it on the bench and you will see.

[hosein_gh (Hosein Ghanbari)]

hi @xbnr99

@xbnr99

Have you checked the frame’s flatness with a level?

they are in a same level

@xbnr99

Since the battery is so heavy, have you checked the center of gravity while the battery is mounted?

yes, copter is physically balanced

@xbnr99

Are you sure the battery is mounted securely and doesn’t shift during flight?

yes

@xbnr99

Does the vehicle hover in stabilize mode and is it stable?

yes copter is hover and fly good in stabilize mode

[hosein_gh (Hosein Ghanbari)]

hi @Anubis
yes after checking frame arms one of them (arm/motor 1) is 5mm upper
but really 5mm upper could make this big unbalance ? and also its on CCW thread not CW
what is your idea ?

[hosein_gh (Hosein Ghanbari)]

yes @Harald
i think CW propellers of Air Gear 350 pack generates less thrust
for testing i ordered 1055 CF propeller to test them
now I’m waiting to receive them then i will share the result

thanks all

[xbnr99 (Jfff)]

Did you notice that on your graph the x axis scales
for the four motors are not the same?

[hosein_gh (Hosein Ghanbari)]

Yes motor 1 is 5mm upper than others

[Anubis (Rick)]

One arm being higher than the others probably wouldn’t cause this, but it would if it is twisted so that the propeller is not level with the ground.

[whatgoesup (Robert Jones)]

Yes it is possible the ccw and cw props could be slightly different.
You could also check how square the propeller hub is on the motor for each one. Install a propeller and secure just firm. Then mark a point on the arm. Take a height to some point on blade. Rotate the propeller 180 degree and check the other blades height above the arm at the same point. Should be approx the same. If not then it is possible the propeller hub is not level.