DJI F450 Shall I be worried or not about the stock motors

[krante]

[h=2]Dji f450[/h]

Hi All,

DJI 450
Stock motors
Stock ESCs
NAZA 2
H3 2D Zenmuse
Gopro
Landing legs VER2 from quadframes

I am all new to quad copters and recently purchased DJI 450 and I might have a problem.

The problem I think I have is that, on take off, one of the motors make strange noises (vibration like almost). It seems to be coming from the front left leg but I could be wrong. I have stored a video here to demonstrate the issue http://youtu.be/PjIVPMHxwAA . It does not occur with 3S packs but with 4S 4000mha batteries. Is the quad too heavy? The strange noise is almost prominent when throttling up / climbing. I also take off in gps mode. Any advise please? I don't want to see my quad fly away due to bad motors so it is grounded until I understand the source of my problem.

Thank you all,

krante​

 

[OneStopRC]

Grab hold of the acorn and see if you have any side to side or up and down play on the shaft, if you do you could have faulty bearing or even a badly cut motor. Either way, you should see about a return on the motor or buy new bearings for it. gothelirc.com has the bearings in stock most times..

 

[photobobga]

At some point you may want to consider replacing the stock motors. There is a large plethora of options. I found the T-motor MT 2216-11 900KV is a worthy consideration.

-Bob

 

[TheUFGadget]

Hi there!

Did you put tape on your props to balance? Have they taken any hard hits? Also, is it a constant noise or rather only at a high RPM? I am thinking if it only happens with the 4S it may be due to speed. Let me know and we can help out further!

 

[haha49]

Did you balance the quad it self? I found with a badly balanced battery it can really shift the weight and make 1 or 2 motors work allot harder. It could be a combination of things. Could even be a bad connection and it's not getting enough power. You can see the arm actually shake back and forth so it was allot of vibration. Me I would check the joints then make sure everything was screwed down well and balance the props then pick up the quad and see if it leans 1 way or the other and balance it well I also use 3 straps to hold my battery on 2 across and 1 length wise as they can shift in flight causing the quad to drift in 1 direction. It just starts leaning over slowly.

 

[sk8brd]

the gains are a bit too high, you can hear that in the motors. i have the same sound when mine were too high and or the balance of the battery is off. i have a similar setup on 4s. spin the props when the motors are off if you hear any abnormal metallic grinding or rattle sounds a bearing could be on its way out. you can also get a vibe meter app for an iPhone or android phone then disconnect the bullets on the motors and throttle up w/out props each motors one by one and see if one motor is worse then the others. you can also feel the arms in your hands and do the same. what are you gains and what size props are you running?

also make sure when you put the battery on it balances on the frame correctly cog wise. i pick up the craft with two fingers on the side of the frame in the middle. it should not tilt in the same direction over and over again but somewhat balance. you can also check the balance by other ways but a simple test is going into manual mode during hover and see what happens. if its front heavy it will tilt frontwards back heavy tilt back etc. keep in mind when you do so half throttle may not be enough to hover, depending on what size prop it could slightly fall or rise. manual mode has no self leveling so if your not comfortable with that make sure the balance of the battery on the craft is where it needs to be. i feel its that but the motors sound a bit over gained. i run the same setup pretty much and use 8 inch props with basic gains 125/125 yaw/120, vertical 110, atti 90. i use slightly bigger battery though on 8inch props.

 

[krante]

Hi there!

Did you put tape on your props to balance? Have they taken any hard hits? Also, is it a constant noise or rather only at a high RPM? I am thinking if it only happens with the 4S it may be due to speed. Let me know and we can help out further!

Hi there,

Thank you for your input. The strange noise only occurs when I am throttling up to climb and stops when hovering ( Fly mostly in GPS mode). Did not have the issue with 3S and I am running 8' CF props. Could this be the gain set too high?

Regards,

Krante

 

[krante]

the gains are a bit too high, you can hear that in the motors. i have the same sound when mine were too high and or the balance of the battery is off. i have a similar setup on 4s. spin the props when the motors are off if you hear any abnormal metallic grinding or rattle sounds a bearing could be on its way out. you can also get a vibe meter app for an iPhone or android phone then disconnect the bullets on the motors and throttle up w/out props each motors one by one and see if one motor is worse then the others. you can also feel the arms in your hands and do the same. what are you gains and what size props are you running?

also make sure when you put the battery on it balances on the frame correctly cog wise. i pick up the craft with two fingers on the side of the frame in the middle. it should not tilt in the same direction over and over again but somewhat balance. you can also check the balance by other ways but a simple test is going into manual mode during hover and see what happens. if its front heavy it will tilt frontwards back heavy tilt back etc. keep in mind when you do so half throttle may not be enough to hover, depending on what size prop it could slightly fall or rise. manual mode has no self leveling so if your not comfortable with that make sure the balance of the battery on the craft is where it needs to be. i feel its that but the motors sound a bit over gained. i run the same setup pretty much and use 8 inch props with basic gains 125/125 yaw/120, vertical 110, atti 90. i use slightly bigger battery though on 8inch props.

Hi there,

Thank you for your input and from your comments above, I think the problem could be gain are set too high. Mine are: 170/170, yaw/150, vertical 120, atti 120. I am also running 8 inch CF prop. The reason why I wasn't getting the vibe with 3S was because the motors were not spinning fast enough, am I right?

Two things I am going to do:
1) Reduce the gain
2) Balance quad in manual mode ( I can fly helis so this shouldn't be a problem)

I will report back of my findings.

Thanks again

Krante

 

[sk8brd]

the way i always have understood it is that when the gains are too high oscillations start to occur. the crafts flight controller is basically trying to over correct itself to remain level. this can happen on 3s as well with gains too high. Any change in weight or prop size may require a change in gains. you should be able to go full throttle burst in any direction in gps/atti modes without oscillation. here is an example i found on youtube..not my video but may help illustrate. the higher voltage, heavier weight and higher prop speed as you mentioned i imagine could of brought it out more. lhttp://www.youtube.com/watch?v=ITJhJ34BiMc

 

[TheUFGadget]

Hi there!

If you have the time try and move the motor on another arm and see if you get the same thing. Preferrably try a different prop as well . Let me know what you get or if you figure it out before then. I always due a process of elimination . I also don't have a lot on "inner motor" knowledge...

 

[krante]

Hi All,

The problem is resolved by reducing the overall gain. I don't think it flies perfect just yet as it wobbles on descend and does not appear locked in when hovering. I will get this down soon though. Thanks everyone for their valuable input.

Regards,