Yaw input and rapid decent induces flipping (Motor? Naza?) CRASH VIDEOS INSIDE

[Craig9080]

Hi Everyone,


Well after taking about a week to pull my head out of my 4th point of contact, I was able to get my naza configures correctly and I was in the air for my maiden. It was super stable but had a few times where I got very small oscillation and just chalked it up to gain. Well on a rapid decent my quad does a fill CCW rotation and lands on its top. After looking at everything I'm pretty sure it was a prop coming loose -lesson learned: use threadlock. Video Below

So I take it up after that and thier is a little of a droning noise I can hear and the performance is less then a smooth. Small pitching motions that I really dont feel great with but I am actually able to get some decent forward flight at the field when I tone the gains down a little bit.

Well this morning I am at my house trying to get some nice aerial shots from above the trees in my back yard and when I decide to take it down all of a sudden I get the horrible rocking and when I try to correct it the whole thing pitched CW and makes a horrible scream (on video...I couldn't hear it from where I was flying) and rockets into the trees. Although the video of me trying to get it is hilarious to my better half, the cause of the failure is troubling to me. Video Below

So I think it is maybe an esc calibration thing, I go one by one on the ESCs and calibrate them. Back in the air I go...but MUCH lower. I try to test things out and after getting into the yaw a little but - BAM - CW roll and she is down. Video Below

So just to check everything out I take her up again over a sandy bit in my year and at about a foot off the ground I see the quad to a hand stand on the right rear motor - scream some ungodly noise - and then after I cut the throttle It puts itself back on the ground. Video Below

I have two concerns


1. What the heck is causing this? Did I bang up a motor on my initial crash and are the bearings just deciding when the want to go?


2. I hear a knocking sound when the motors are at low speeds almost like cogging, should I be concerned?




Any help you guys can offer would be outstanding, my FPV gear will be here next week and would like to be able to fly without KNOWING that it is just a matter of time before my quad decides to take a dirt nap. Thanks




My Setup:


QAV500
FM-4006-13 740kv Motors
10x4.5 GF props
30A iPeaka SimonK ESCs
Naza-M v1 w/ GPS
Futaba R3110dps Pcm Rx
Futaba T9CAP Super


P.S. I did post this on RCG as well. I'm not trying to clutter the forums, but their seems to be a much more helpful bunch here.

 

[ewr]

Looks like the same motor every time, no? try labeling then swapping motors to different arms and see if it does it on only one of the motors, or ESC. When you use yaw input I believe it puts a lot of stress on the motors because they are slowing/speeding very quickly to produce the torque to yaw, so maybe one of your motors is pulling to many amps and when you try and yaw it heats it up or pulls too many amps for the ESC and it shuts it down for a second as most will do. I noticed on a small cheap quad of mine that as I crashed, and crashed, and crashed more...it started to drop the same motor at first only with the heaviest AUW (5000mah battery)...as time went on that motor would cut out randomly especially after a fast decent and recovery, or intense yaw input...but if I used a 2650mah battery it would take whatever flying I could throw at it. Few crashes later....it would do the same with the 2650 and was only flyable with 1600mah batteries. I replaced that ESC and it did it LESS, but it wasn't until I replaced the motor that it stopped. I think when you bang up these motors and hurt the bearings it just puts too much load on them causing the amps to rise and ESC to shut down.

 

[CrashMaster]

I know it is expensive to do but if you have a hard landing or crash it is always wise to replace the motors. They run at so fast that the tiniest bit of damage or pushing out of true is amplified when the rpm goes up under load, this has two results - Massive vibration and a massive amperage draw.

Vibration can result in a self destructing motor and the amperage increase can cause damage to the motor, wiring, esc and lipos.

 

[swisser]

Craig, with respect you're going about this all wrong. This is the kind of problem you ought to be trying to solve on a bench, unless you've got endless time and money to keep repairing the thing when you crash it!

So what's the right way to sort this? To use my catch phrase, it's certainly nothing to do with gains. At least you're not blaming a flight controller software upgrade which is what most people (erroneously) blame.

Motors should not make odd, weird, intermittent noises. Not ever. For a given throttle they should make a very continuous sound. Take the props off and don't leave the nuts on the top of the spindle either in case they fly off. Now connect each ESC directly to the throttle in turn. At each of 25%, 50%, 75% and 100% let them run for a good five minutes. They won't have as much cooling as normal (no big spinning cooler above them!) so check they, and your ESCs, don't get too hot. If there is at any point anything other than a continuous even tone, replace that motor. If they all check out ok, once you've done the last one go back and do the first one again, because by now you'll know what it ought to sound like.

If all motors check out ok then I would suspect a bad connection somewhere between battery, ESC, flight controller and motors. Only sure-fire way to solve that is to redo them all.

Oh and taking off from sand is likely to be catastrophic. Sand is really bad for motors - think about it - those things are pretty small and spinning at thousands of RPM. Take off from sand and you've got a ton of the stuff blowing around every which way and it's bound to end up in the motors. Stop doing that. Take off from somewhere else, lay something big and flat on the sandy ground, or hand launch/land.

 

[Silverburn]

That droning sound is a motor out of balance or with damaged bearings, possibly on route to complete failure.

 

[Craig9080]

Craig, with respect you're going about this all wrong. This is the kind of problem you ought to be trying to solve on a bench, unless you've got endless time and money to keep repairing the thing when you crash it!

So what's the right way to sort this? To use my catch phrase, it's certainly nothing to do with gains. At least you're not blaming a flight controller software upgrade which is what most people (erroneously) blame.

Motors should not make odd, weird, intermittent noises. Not ever. For a given throttle they should make a very continuous sound. Take the props off and don't leave the nuts on the top of the spindle either in case they fly off. Now connect each ESC directly to the throttle in turn. At each of 25%, 50%, 75% and 100% let them run for a good five minutes. They won't have as much cooling as normal (no big spinning cooler above them!) so check they, and your ESCs, don't get too hot. If there is at any point anything other than a continuous even tone, replace that motor. If they all check out ok, once you've done the last one go back and do the first one again, because by now you'll know what it ought to sound like.

If all motors check out ok then I would suspect a bad connection somewhere between battery, ESC, flight controller and motors. Only sure-fire way to solve that is to redo them all.

Oh and taking off from sand is likely to be catastrophic. Sand is really bad for motors - think about it - those things are pretty small and spinning at thousands of RPM. Take off from sand and you've got a ton of the stuff blowing around every which way and it's bound to end up in the motors. Stop doing that. Take off from somewhere else, lay something big and flat on the sandy ground, or hand launch/land.

Thank you, this is some great advice.

I have already ordered new sets of bearings for all of my motors, I'm very sure that at least one of them is bad as I can now hear a tick when I spin it manually. This makes me concerned that one of my motors was bad from the start as that odd "cogging" noise was always present even on all 4 new motors without props. Could this be an ESC issue?

Bench testing sounds like a great idea, I really did not think of doing one motor at a time connected directly to my receiver - that makes allot of sense.

Sand - Again, makes sense. We have a ton where I live but I can manage to find the grassy bits.

 

[Craig9080]

Looks like the same motor every time, no? try labeling then swapping motors to different arms and see if it does it on only one of the motors, or ESC. When you use yaw input I believe it puts a lot of stress on the motors because they are slowing/speeding very quickly to produce the torque to yaw, so maybe one of your motors is pulling to many amps and when you try and yaw it heats it up or pulls too many amps for the ESC and it shuts it down for a second as most will do. I noticed on a small cheap quad of mine that as I crashed, and crashed, and crashed more...it started to drop the same motor at first only with the heaviest AUW (5000mah battery)...as time went on that motor would cut out randomly especially after a fast decent and recovery, or intense yaw input...but if I used a 2650mah battery it would take whatever flying I could throw at it. Few crashes later....it would do the same with the 2650 and was only flyable with 1600mah batteries. I replaced that ESC and it did it LESS, but it wasn't until I replaced the motor that it stopped. I think when you bang up these motors and hurt the bearings it just puts too much load on them causing the amps to rise and ESC to shut down.

This will give me some more motivation to shorten my motor wires to lesson that amp draw. I also have a eLogger v4 that I will be using now to log amp draw even on bench testing.

 

[Craig9080]

I just realized that I had my maiden video set to private. Please take a look a notice the "cogging" sound from the get-go. Anything to be concerned about?

 

[Craig9080]

So after replacing all bearings and ESCs it is flying great minus a few excess vibrations. 90% sure it was actually and ESC issue as I had a tough time calibrating one for throttle input when I was doing my rebuild. Anyway, here is a great vid of it flying recently.

Thanks again for everyone's help!