Motor stops twice in mid air on hexa

Q

Quinton

Active Member
Had my first major scare this morning while out flying.

Just took off and started to check everything was working, pitch roll..started to check my yaw and all of a sudden one of the motors stopped, and a whining pitch came out of it.
I still had control of it, it did not start yawing, but I had no yaw control at all.
Luckily I was not so high, so I just lowered it to the ground as quickly as possible.
I wasin that much of a panic that I did not take note of which motor it was.

I checked it all over again, and started the engines all again..this time I just kept it close to me and it flew OK or the next 13 mins.
I then changed my lipos and sent it up again, after 2 mins the same thing happened, like the propeller just locked up.
This time I was a bit more calm and brought here down, but kept the motors spinning this time, and seen that it was motor 2 on the Skyjib 6 Ti.

Now I will have to go through everything to find out what the problem is, however..where exactly do you start.
Has anyone experienced anything like this before.
I have read that it should have started oscillating if a motor fails, but obviously I know that this was not the case for me.
Thankfully it didn't happen when I was too far away or going with much speed, or it may have been a different case.

In a way I am sort of glad it has happened when it did, as it has made me a lot more wary of what could happen.

Anyone any thoughts on what should be my next steps?
Hobbywing 40A opos ESCs with tiger 3515-15 motors and Droidworx PDB

Have about 10 hours flight time with this new setup.
 

S

Silverburn

Member
Nope, mine did this too, imediately switching my TBS Disco from 3S to 4S.

Stopped once, and crashed, motor whining. Checked over...everything looked ok, spun smoothly etc. Attempted a test launch again, and...a couple of twitches, then magic smoke from the ESC. Motor was now jammed solid. New motor and new ESC.
 

J

jes1111

Active Member
Sounds like a power problem more than a control glitch. When you landed it that second time, was anything hot? The motor, the ESC, the wires, the connectors? Your next step should be to swap the affected ESC with another arm and see if it happens again (and on which arm), etc. - standard "process of elimination".
 

Q

Quinton

Active Member
Yeah .. problem is how do I keep testing now, it seems to happen when I put the yaw full on only, and I don't want to try my luck too much with something thats worth quite a lot of money 10 ft up in the air.
The motors are always cool to the touch, its hard to check the ESCs as they are buried under the plate, and not so easy to get at with the crash cage.

I will swap the ESC with another motor and see what happens, either way that is going to tell me if its an ESC or a motor I suppose.
Think I will hook up my Wireless Data Link Module also (which I have not used yet) to a computer next time I take it out, see what that says.
Actually counting up my lipos there was about 6 hrs and 40 mins flight time total.

I did change the yaw gains just before the problem, as I thought it was a bit unresponsive lately..hmm scary times ahead.
Just before I was about to put a gimbal on it too, that will have to wait now.
 

J

jes1111

Active Member
Mmmm... could be a timing problem or a PWM range problem if it only happens on full yaw - check that the timing setting is the same in all ESCs and your throttle range calibration is good for all ESCs.
 

Q

Quinton

Active Member
jes1111 said:
Mmmm... could be a timing problem or a PWM range problem if it only happens on full yaw - check that the timing setting is the same in all ESCs and your throttle range calibration is good for all ESCs.
Click to expand...

Will do, just as soon as I work out how to do that :)
I did do the throttle calibration when I first got them, is that something that you would have to do often, I would have thought only the once?
The ESCs were pre-programmed before I got them, I will buy a programming card for them, to give them a check.

These are the ones..
http://www.hobbywing.com/uploadfiles/sx/file/manual/HW-01-V4.pdf

Strange how its only happening now after more than 6hrs flight though!
Any insights on how I actually check if there's a PWM range or timing problem, any links to anything or some gear that can check that.
I'm learning as I hit each new problem..and its getting more expensive the more I learn :)

Just glad it happened on a Hexa and not a quad, or it would have been even more expensive.
 

S

Stacky

Member
If you have a set of old props you can chop them back to half size. You can do this by using a nail on a bit of wood at a set distance from your central hub and have them reasonably balanced.
You can then have your hexa safely secured to a bench etc and then give the Hexa full yaw inputs and the half props give you a loading without the Hexa being able to lift off.

Quinton said:
Yeah .. problem is how do I keep testing now, it seems to happen when I put the yaw full on only, and I don't want to try my luck too much with something thats worth quite a lot of money 10 ft up in the air.
The motors are always cool to the touch, its hard to check the ESCs as they are buried under the plate, and not so easy to get at with the crash cage.

I will swap the ESC with another motor and see what happens, either way that is going to tell me if its an ESC or a motor I suppose.
Think I will hook up my Wireless Data Link Module also (which I have not used yet) to a computer next time I take it out, see what that says.
Actually counting up my lipos there was about 6 hrs and 40 mins flight time total.

I did change the yaw gains just before the problem, as I thought it was a bit unresponsive lately..hmm scary times ahead.
Just before I was about to put a gimbal on it too, that will have to wait now.
Click to expand...
 

C

Chalagi

Member
I had my F450 to tip down in the left front while hovering. So I switched the motor with the opposite front motor on the right and then it was tipping on the right side. After taking out the bearings and replacing them everything was all good again
 

Q

Quinton

Active Member
Just wondering if this could be the problem..
I opened up the Skyjib today to have a look at the ESCs and noticed a really small tear in the cable exposing the wires.
Maybe this is the problem causing a short and stopping the motor?

View attachment 15195View attachment 15196
 

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J

jes1111

Active Member
Is that a tear or a melt? Either way (and assuming that's the suspect ESC), I'd extract that ESC and strip the heat-shrink off to give it a thorough inspection before replacing the wire. What about the capacitors? - any sign of bulging or weeping on the exposed ends? If there is (even the slightest) then they should be replaced (with higher-spec units than the originals e.g. Panasonic Low ESR).

btw - I don't like the look of those wires - you can see the ends where they emerge from the heat-shrink have been over-heated during soldering - looks like the solder has wicked up the wire well past the heat-shrink. This is the crucial problem with soldering connectors: the wire will be vulnerable to fatigue breakage at the point where the solder stops since it is mechanically unsupported. On a "good" solder job the stiffened part of the wire will fall within the subsequently applied heat-shrink, thus affording it mechanical support to reduce the chance of vibration-induced internal breakage.

EDIT: these are the capacitors I use: http://uk.mouser.com/ProductDetail/...=sGAEpiMZZMtZ1n0r9vR22f2plZjWOZXTu0LqHMfIqXE=
 
Last edited by a moderator:

Q

Quinton

Active Member
jes1111 said:
Is that a tear or a melt? Either way (and assuming that's the suspect ESC), I'd extract that ESC and strip the heat-shrink off to give it a thorough inspection before replacing the wire. What about the capacitors? - any sign of bulging or weeping on the exposed ends? If there is (even the slightest) then they should be replaced (with higher-spec units than the originals e.g. Panasonic Low ESR).

btw - I don't like the look of those wires - you can see the ends where they emerge from the heat-shrink have been over-heated during soldering - looks like the solder has wicked up the wire well past the heat-shrink. This is the crucial problem with soldering connectors: the wire will be vulnerable to fatigue breakage at the point where the solder stops since it is mechanically unsupported. On a "good" solder job the stiffened part of the wire will fall within the subsequently applied heat-shrink, thus affording it mechanical support to reduce the chance of vibration-induced internal breakage.

EDIT: these are the capacitors I use: http://uk.mouser.com/ProductDetail/Panasonic/EEU-FR1H471/?qs=sGAEpiMZZMtZ1n0r9vR22f2plZjWOZXTu0LqHMfIqXE%3d
Click to expand...

No its def a tear, I can see where it was rubbing.
Will just replace the whole thing, but aren't we going a bit overboard with the other stuff.
I know you are going to say about, how much money is in the air etc..but.

It was actually my dealer who soldered them on for me, and he has made MANY flying machines for lots of professionals, just seems the heat shrink is a bit short, granted the others do look better?
As for the capacitors the one on it is 330uF, but again he says that hes never had an ESC fail yet and he unlike us spends 10s of thousands of pounds on this stuff.

I do like being helped and appreciate it very much, but is there maybe just going a bit too far with changing components as really they should be good when you buy them?
 

J

jes1111

Active Member
:) I recall a recent conversation in which I mentioned the need for sleeving to protect wires where they pass near to edges or through holes in the carbon fibre. And you're suggesting it's "a bit overboard" when you have in front of you a rubbed-through wire that has (probably) caused an in-flight failure for you? You can't just write that one off to bad luck and "hope" that it won't happen again. The only rational response (whether it caused your motor stoppage or not) is to sleeve every single wire on that craft where it comes even remotely close to a carbon fibre edge. Aviation safety (the real, Jumbo jet kind) is heavily about thoughtful and rigorous design work up-front followed by the ruthless pursuit and correction of anything and everything that causes in-use failures. I don't see why our MR world should behave any differently.

Re: the capacitors - the capacitance value is not critical - the voltage rating, the temperature rating and the low ESR value are the more important factors. Those capacitors take a hammering whilst doing their job - they will deteriorate over time and they will eventually fail. Poorer quality units will fail faster. China is awash with counterfeit components - just because they say "Rubicon" on them doesn't guarantee that they are. A bulging top is a sure sign that the component is dying - to not change it immediately is inviting disaster. I change all of mine for Panasonics as soon as I get them - at £0.35 each for known-good components it is certainly one of the most cost-effective steps you can take to improve reliability.

I don't doubt that your dealer is sincere but it is flawed logic to jump from "my dealer has never had an ESC fail" to "ESCs never fail". Likewise with soldered connectors.
 

Q

Quinton

Active Member
jes1111 said:
:) I recall a recent conversation in which I mentioned the need for sleeving to protect wires where they pass near to edges or through holes in the carbon fibre. And you're suggesting it's "a bit overboard" when you have in front of you a rubbed-through wire that has (probably) caused an in-flight failure for you? You can't just write that one off to bad luck and "hope" that it won't happen again. The only rational response (whether it caused your motor stoppage or not) is to sleeve every single wire on that craft where it comes even remotely close to a carbon fibre edge. Aviation safety (the real, Jumbo jet kind) is heavily about thoughtful and rigorous design work up-front followed by the ruthless pursuit and correction of anything and everything that causes in-use failures. I don't see why our MR world should behave any differently.

Re: the capacitors - the capacitance value is not critical - the voltage rating, the temperature rating and the low ESR value are the more important factors. Those capacitors take a hammering whilst doing their job - they will deteriorate over time and they will eventually fail. Poorer quality units will fail faster. China is awash with counterfeit components - just because they say "Rubicon" on them doesn't guarantee that they are. A bulging top is a sure sign that the component is dying - to not change it immediately is inviting disaster. I change all of mine for Panasonics as soon as I get them - at £0.35 each for known-good components it is certainly one of the most cost-effective steps you can take to improve reliability.

I don't doubt that your dealer is sincere but it is flawed logic to jump from "my dealer has never had an ESC fail" to "ESCs never fail". Likewise with soldered connectors.
Click to expand...

I agree with you 100% regarding sleeving every wire that comes close to a carbon edge, it was my intention to do so but was too busy "testing" the new setup.
Now that I have her apart it will be my first job.
As for the capacitors, I am not the greatest solderer in the world, so the last thing I want to start doing is taking things apart to solder new parts (which I have no idea how they work) on.

I am just hoping this was the cause of the motor stoppage (hopefully it was) but it has made me stop and think "what if" a lot more now, and I am sort of glad it did happen the way it did.
May I ask what ESCs you actually use yourself?
 

J

jes1111

Active Member
I use ZTW 40A ESCs - got some a long time ago on a recommendation and I've stuck with them since - "better the devil you know" etc. ;)

Re: soldering - it's really, really worth getting into it. Not unsurprisingly, the more money you spend on the soldering gear, the easier it is. Many people think soldering is difficult because they first try it with a bum soldering iron and never progress!
 

Q

Quinton

Active Member
jes1111 said:
I use ZTW 40A ESCs - got some a long time ago on a recommendation and I've stuck with them since - "better the devil you know" etc. ;)

Re: soldering - it's really, really worth getting into it. Not unsurprisingly, the more money you spend on the soldering gear, the easier it is. Many people think soldering is difficult because they first try it with a bum soldering iron and never progress!
Click to expand...

I bought a good soldering iron from Maplins and had a few bad experiences at the start, so I then bought a really good gas one.
The problem wasnt the soldering irons at all, it was the fact I started off with lead free solder, as soon as I changed to 60/40 solder then it got a LOT easier after that.
I just don't like the thought of soldering things that don't need soldering just in case.
Just want to get this "problem" sorted before I put a 5D Zenmuse underneath it, thats why I am kind of glad it happened when it did.
Although I still have to find out what the problem is, but next step is to change ESC and swap with a different motor.

Do you thnik closing it with liquid tape would be a bad idea, the wires arent damaged at all, they are just showing, and its def a rub mark not a burn mark.
 

J

jes1111

Active Member
Liquid tape would be a temporary band-aid, but the problem with the wire is that you don't really know if there's any broken conductors inside. I understand what you mean on the soldering thing - maybe a quick trip to your dealer? - would only take him minutes.

Ah, yes - lead-free solder - PITA that stuff!
 

iceman

iceman

Member
Instead of protecting each wire where it enters/exits the centre plate (18 wires) why not just add protection to the plate with a large rubber gromit, much quicker and easy to do.
 

Q

Quinton

Active Member
iceman said:
Instead of protecting each wire where it enters/exits the centre plate (18 wires) why not just add protection to the plate with a large rubber gromit, much quicker and easy to do.
Click to expand...

I've always though Droidworx should have already been doing this with their design at least on the ends of their booms.
Where exactly can you buy large rubber grommets in the UK?
That cut actually came from my PDB, but ts only a matter of putting 1 sheath over each of the 3 motor/esc wires.
 



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