5 inch Alien
Full KISS set up

Machine ran great all spring, mid July had a light tumble onto a gravel road.
Replaced props, noticed ossolation around mid throttle punch.......

Replaced motors and props, noticed a little improvement.......

Played with data logger and set notch filters accordingly, again maybe a little improvement, not a whole lot.........

I have been flying it all summer and fall because it has been more of a nusciense than an outright problem.

Fast forward to yesterday, started up like normal, dropped goggles on, armed up, went to lift off and the quad flipped itself over, right into a little mud spot, not submerged in water and mud, just enough to cover the front end enough that I had to do a little disassembly to clean it up.

I took it out today, and the vibration is s LOT worse and when in forward flight there is a sound like a blade is fluttering........

Changed props same thing, the gap between the motor bells and bases looks ok, can't see any missing magnets (Emax 2205 2350 motors)

Ext up is a complete teardown I think, also, as far as I can tell all solder joints look ok, but need to take it apart to inspect for damage.

Any thoughts are appreciated !
Danny Z

I'd put my money on a bent motor bell. If you can't see a difference in height between the base and the bottom of the bell when you turn the bell then you don't have a bent shaft. A collision with a hard surface could easily deform the bell though. Try inspecting the motors from above and see if the side of the bell looks the same as you rotate it.

Check also for up and down movement on the bells which could be caused by the bell having moved on the shaft or from the bearings being worn out.

The new problems would point to an ESC being on the way out. They are easy to damage in crashes if you haven't disarmed early enough.

Unseen, Thank you very much for your reply,

I have been wondering what the symptoms of an ESC on the way out might be,

As soon as I made the initial post, I got home and did a tear down of the machine, the motor bells look good, no deformity, no excessive vertical play in the shafts when I pull up on them

BUT !!!!, as I was disassembling, I discovered that one of the bolts that holds the right from arm in, IS SLIGHTLY BENT, it needed a little extra work to get out, but there is a definite bend in it. I must have had a crash at some point that did the damage because when I built the bird it was definitely not bent !!!!

After I got everything apart all the carbon looks ok, so Im thinking at this point to just go ahead and replace the esc's and 
give it a test flight..........what do you think ?


One more question, do flight controllers ever "wear out ?  my initial thought is no, or maybe after thousands of flight hours maybe they do, but I definately dont have that kind of time on my equipment  !!!!!

Thanks again  !!!


DZ

Nice find!

If that bent screw also indicated a loose arm, that would certainly account for the vibration. Is this the same arm that you started flipping towards?

The most fragile part of an ESC is the ceramic capacitors, particularly if they are near the middle of the board and run along the arm. As they are made from ceramic, they really don't like to be bent, not even a tiny amount. On a flight controller, there are not only ceramic capacitors, but there's the IMU. An IMU is a small marvel of a micro machine.



It's also a mechanical thing, no matter how small. The thinner the flight controller's PCB, the larger the chance that you'll break the IMU in a bad crash. Frames that use the PDB and flight controller as structure are particularly prone to this.

In general, all electronic components are sensitive to mechanical stress. Bending or twisting is the worst type and tends to break ceramic capcacitors, MEMS devices and integrated circuits in particular.


So, you probably could say that the electronics in a quadcopter will wear out. The more often and the harder you crash, the faster your electronics will fail. It's pretty much unavoidable.

Thank you for the awesome explanation !

I honestly dont know which way the quad flipped on take off the other day.
 
I know on the Alien that the PDB is a very thick component, with that being said, This particular machine definitely developed its oscillations  before I soft mounted the FC.........sssooooo either esc damage or FC damage or both ???????

 This may be a multi step process to figure out the issue, I currently have 2 spare esc's on hand and 2 FC's.

I think I will replace the esc that was on the arm that had the bent screw, and give it a test flight. we have rain here for the next day or two here in CT, I may not be able to get a test flight in until next Thursday, but I will report back with what I find.

If that doesnt solve the issue, I may replace the other 3 esc's before I think about putting in another FC. I have put quite a few packs through this machine since April !

And no, the arm that had the bent screw was tight, none of the arms were loose at all..............................

stay tuned !!!!!!!

Danny Z

Good luck!

It can be tricky to work out what's wrong sometimes. It's much worse if there is more than one thing wrong at the same time.

Does KISS have a black box feature? That would tell you which motor/ESC was giving the problem where the quad flips.

I have run a "blackbox" data logger earlier this summer, it showed where the noise was, but not much improvement after I applied the filtering.

I also tried using TPA, but not much luck with that either, and yes, it can be very frustrating if more than one thing is going wrong at the same time !!!!

I will be replacing one esc tomorrow night, but it may be thanksgiving morning before I can get a flight in........stay tuned 

Danny

I hope you get it fixed, but i also read about a few cases of kiss fc's going bad... like, the gyro sensors broke or something like that.

I don't doubt this can happen with any type of fc, it's just the kiss is not as cheap to replace as certain others...

Thank you for the suggestion about the FC................

So I replaced the ESC on the arm that had the slightly bent screw in it, I just got back from a Thanksgiving day flight !

While there was some improvement, it was definately not enough to call it fixed................

I was going to replace the ESC's one at a time and then move on to the FC, BUT, I am now thinking I may just replace the FC next and see where I end up..........

Stay tuned, I will try and get the FC swapped out later today, and I am working tomorrow (Cant turn down overtime !!, got to keep my drone fund solvent !!!!)

At a minimum, I should be able to get out flying on Saturday, I will post an update then. 

Danny Z

11/25/17 Update:

Was out flying yesterday and a friend recommended re-flashing the FC, So I re-flashed both the FC and the ESC's.....................and it did not make a bit of difference, so I am torn between swapping out all the ESC's one at a time, or just swapping out the FC next............

I'm also wondering if a cracked PDB could be the issue, but the PDB on the Alien is crazy thick...............................

Thoughts ???

Danny Z

I would try whatever is easier to do... I think replacing the fc might be less work.

Edit. Have you tried to set a large deadband in the fc firmware, just to make sure it's not something with the radio pots...

What is a dead and?
Does it reduce control input from the stick movements ?

(28-Nov-2017, 12:27 PM)DannyZ Wrote: What is a dead and?
Does it reduce control input from the stick movements ?

Basically yes, if you increase deadband in the fc, you have to move sticks further before they start having an effect (it increases the deadzone at center of sticks). You can use this if you have radio jitter.

Default is 2 on kiss i think. On very old firmware it was not adjustable though.

Edit. I don't think it's an issue here, but setting a ridiculously high deadband would exclude your radio/rx as a possible cause of problems.

Understood, thank you for the explanation, I am really struggling with just swapping out the FC, or sticking with my original lpan to swap out the ESC's 1 at a time, then move onto the FC..................

I have to work late all this week, plus I am working this Saturday, so it will be Sunday before I can do any work on the bird.........................BUT, I think it will be the FC next...............swap it out Sunday morning and test fly if the weaather is good, I will update Sunday night !!

DZ

OK, 
the new fc definitely helped out a LOT, HOWEVER, I am still getting some definite jitters at full throttle now.

I still think there may be either:

 1-a bad ESC
 2-A bad motor

Even though I replaced the motors 2 months ago, does not mean one of them is not out of balance, visual inspection of the motors does not revel any scratch's , nicks or deformities and the gap between the bottom of the bell and the base of the motor appears to be the same when I rotate the motor by hand...................

so the investigation continues.....................

but like I said before, the new FC definitely made a BIG difference.

stay tuned, although here in the Northeastern part of the US, we may be getting some of that white crap soon.............