Burnt out motors

[Carter7868]

So just recently I put together my very first drone. I had a couple of flights and then 1 of my motors started shaking back and forth. I Un-Armed the motors straight away and then I went and checked the connections. It looked like the motor had a lost connection so I went ahead and fixed the connection. Once I went out to test the quad again the motor didn't shake/vibrate this time it just made a noise and didn't move at all. So I contacted the seller and they agreed to send me another one for free. Then I went out and tested it again but this time a different motor had the same problem. Thinking it was the connection I checked it but there was no lose connections this time. Do you guys think they're just bad motors or is it my newbie mistake? Can motors just die that easy if 1 wire is loose? Here is my part list below.
APM 2.8
Emax XA 2212 980 kv Motors
Simon 30A Esc's
Realacc / Matek HUBOSD PDB
Venom 8000 mah 20c 2 cell
If you need any more information please feel free to message me and I will be happy to send anything that will help.

 

[Jackson]

Seems odd that it has happened to more than one motor. Do the affected motors seem overly hot? When you spin them by hand do they feel gritty? One thing to check is the length of the mounting screws. If they are too long they can be going into the motor and scraping the actual copper wire windings. Take a look in bottoms and look for any signs of scraping.

 

[Carter7868]

Do the affected motors seem overly hot?

The Motors were not hot when I checked them.

When you spin them by hand do they feel gritty?

They Feel Normal When I spin them By Hand. I Did some research and it said If I put two wires together and spin the motor it will spin less freely then when 2 wires are not connected. So I tried this and when I put motor wires 1 and 2 together and they had more resistance, And then I put Wires 2 and 3 together and it did not change it, it still spun without resistance. Then I tried 1 and 3 and it still spun without resistance. So what I think is wrong is that wire number 3 is somehow disconnected? But how does the wire just disconnect that easy? I used a multimeter after to check resistance and wire number 3 is not showing a connection with any of the other wires.

One thing to check is the length of the mounting screws

Mounting Screw length is good, No sign of scraping.

 

[Gyro Doctor]

So what I think is wrong is that wire number 3 is somehow disconnected?

That is correct.
Quad motors with three wires are aka "Delta BLDC Outrunner" motors (electrically think of basically a triangle with a wire at each point).
If, as you've done, found continuity from any two wires to another but one wire that has none to any others then it's a bad connection there (#3).
Disassemble the motor and find the connection of that wire to the stator coils then resolder it and you'll be good to go !

 

[mozquito1]

Reflow the solder joints. Got any pictures? I got a crappy racerstar that had about 2 or 3 strands of core in a wire that jerked after a bit. Pretty much the same as a bad solder joint.

 

[Carter7868]

Got any pictures?

Also, Earlyer someone was talking about the screws scraching? How would that even happen since the coils turn with the motor? The Picture above shows the motor. I am Kinda confused on how to solder any broken wire strands that are in there since the bottom piece is in the way. How would I remove the bottom peice?

 

[mozquito1]

You can't. It's the prop screws that catch on the windings. The bottom ones just get squeezed then ultimately snap with vibration fatigue. That looks fine from what I can see. Well Atleast the one wind I can see. Have you not got a servo tester.
Only a few £$ easy to test every esc & motor as they come in the post b4 you put it on a build. So then you know any jerked movements is down to esc or dodgy soldering.

 

[Jackson]

If you look carefully, you'll see that overly long screws will come in contact with the windings in at least 3 of the mounting holes.

 

[Carter7868]

Ok, so how am I supposed to re-solder the wires if I cant get to them? Also, I just checked and my screws don't hit the motor coils. I don't have a servo tester but when I try the motor in a working ESC it still doesn't work so I know that its the motor.

 

[Gyro Doctor]

How would that even happen since the coils turn with the motor?

The coils do NOT turn with the motor (hence the term "outrigger") the coils are stationary and the "bell" (top half with the magnets in it)
is what spins.

Moz, mounting screws being overly long CAN TOO cut into the coils and create short circuits ! The coils not moving has nothing to do with a screw's
ability to compromise the thin enamel insulation on the wire and shorting out the coil.

A fine pencil tip soldering iron is used to reconnect the stator wiring to the motor leads (or repair a broken coil winding) by working through the bottom of the motor.
If the stator wire has broken off within the the motor lead then the (new) tip of the broken stator wire may need to be scraped with an exacto knife to remove some insulation and retinned before trying to solder the connection. It's a simple process that's not that hard to do, and even if it doesn't work you've lost nothing in trying to revive a motor that's already dead.

 

[Carter7868]

A fine pencil tip soldering iron is used to reconnect the stator wiring to the motor leads (or repair a broken coil winding) by working through the bottom of the motor.
If the stator wire has broken off within the the motor lead then the (new) tip of the broken stator wire may need to be scraped with an exacto knife to remove some insulation and retinned before trying to solder the connection. It's a simple process that's not that hard to do, and even if it doesn't work you've lost nothing in trying to revive a motor that's already dead.

Ok thanks, Now I just have to try to find the disconnection. Does anyone have a diagram on what wires are going where so I know where to look?

 

[Carter7868]

Ok, I can't seem to find the break in any of the wires. Should I try to find a place that can re-wind my motors for me?

 

[RENOV8R]

It's a $10 motor, it would cost more to fix than what it's worth. Buy a new one and grab a spare or two while you're at it.

 

[mozquito1]

Ok, I can't seem to find the break in any of the wires. Should I try to find a place that can re-wind my motors for me?

It be cheaper to do it yourself.

 

[edward sox]

I don't think so. It is not related to being cheaper than usual. I have just bought the cheapest motors that have different KVs and simonK ESC. I could work some motor easy but some were very hard for me. I did some wrong with motor cables. I tought before that ESC has 3 out cables and the middle cable of ESC is related to yellow cable of motor. But not.

Then I just changed connection places of yellow and black cables each other then It worked like this: