problem with 1 of 4 rotors on Phantom 2 Vision

[bighertz92]

After recently purchasing my Phantom a month ago, I am having an issue with one of the rotors. For sake of context, the problem started due to a crash from about 15 feet off the ground. I was unaware that you can override the Fly Home program, and wish I had because it did not account for a tree right before landing and got caught up in one of the low hanging limbs before falling directly on one of the rotors.
I was able to bend the frame back into shape fine, but even with no interference from anything else, the one rotor does not spin correctly. When I turn on the drone to compare it to the other three rotors it will spin in a "sticky" rotation as if there is some sort of internal interference keeping it from accelerating fluently. Can someone please shine some light on how to bring it back to a flying condition. I am fine with replacing it if need be, but I have several things here in Chicago that I would like to film from the air this weekend if at all possible.
THANKS!!!!

 

[captej26]

Bent what back in shape? Body? Was one of the arms bent?

 

[RipperFox]

I've read a few post about people having the hard landings and the "sticky" motors directly afterwards like yours. The ESC was the culprit.

So I am suggesting that you make sure its the motor before ordering. Maybe swap two motors, and see if the problem follows the motor or stays with ESC.

 

[bighertz92]

RipperFox: great heads up response thank you! I have no experience working with the motherboard or internal components and would rather learn through trial and error than send it off for maintenence.

Quick Follow Up Question: What is ESC (where is it located) and what is needed to swap out motors to test it

 

[CrashMan]

You need to split the phantom shell, there is one esc (electronic speed control) for each motor in each arm. There are a few vids on youtube that will show you how to do this. ripper is right, swap motors with the one that turns the same direction, if the problem stays with the suspected bad motor, your esc is ok, just replace the motor, if the problem stays in the same arm, replace the esc. A word of caution, when melting solder to remove a wire from any circuit board, make sure the solder has melted well enough before pulling on the wire or you will pull the little pad on the circuit board off with the wire. Dont let that scare you though, it's easy to do this. Check youtube, you will find a tutorial to fix almost anything on the phantoms.

 

[RipperFox]

You need to split the phantom shell, there is one esc (electronic speed control) for each motor in each arm. There are a few vids on youtube that will show you how to do this. ripper is right, swap motors with the one that turns the same direction, if the problem stays with the suspected bad motor, your esc is ok, just replace the motor, if the problem stays in the same arm, replace the esc. A word of caution, when melting solder to remove a wire from any circuit board, make sure the solder has melted well enough before pulling on the wire or you will pull the little pad on the circuit board off with the wire. Dont let that scare you though, it's easy to do this. Check youtube, you will find a tutorial to fix almost anything on the phantoms.

With crashmans cautions, you should invest in the proper tools first too. A good soldering iron, solder wick, etc.
This guy is working on an ESC.

 

[bighertz92]

Thanks guys. This forum is incredible. I'm just wondering whether you two think that the soldering is necessary and wanted to mention one more thing here before doing so. The motor is "sticky" and refuses to turn fluently even when manually spun by hand. That being said, should I still solder and test the ESC?? If the motor does in fact need replacing, is there a retailer in Chicaggo that would carry the spare motor for pick up tomorrow? We do not have a local DJI tetailer

 

[bighertz92]

Thanks guys. This forum is incredible. I'm just wondering whether you two think that the soldering is necessary and wanted to mention one more thing here before doing so. The motor is "sticky" and refuses to turn fluently even when manually spun by hand. That being said, should I still solder and test the ESC?? If the motor does in fact need replacing, is there a retailer in Chicaggo that would carry the spare motor for pick up tomorrow? We do not have a local DJI tetailer

 

[singapore_phantom]

Big Hertz, does the engine make a grinding sound, any kind of sound, when you rotate it by hand? Or does it just feel like it turns with friction without any sound whatsoever? Is the friction along the entire revolution, i.e. 360 degrees, or only in part of it?

 

[rjstone]

I'm hardly an expert as I just bought one of these, but I managed to clip a tiny tree when I was flying really low, and it caused a flip and crash on wet grass. Immediately afterwards one of the motors was "sticking" like this and spinning very slowly and very irregularly. In my case all I had to do was blow out the motor area with a duster can and let everything dry. Either some water was in the stator coils, or maybe some got onto the ESC board on that arm, but whatever it was I got it out and it returned to normal after that.

In case you don't know, the motors on these things are basically step motors where the rotor gets pulled into a specific position by energizing a specific coil, then to keep the motor running a timing circuit has to switch on the next coil at the right time for the right amount of time depending on the current speed. If one of the stator coils doesn't switch "on" at all (due to a short, broken wire, etc) then the rotor doesn't keep moving at the expected speed and so its not in position for when the next coil switches on. Sometimes it gets pulled forward by the next coil that's too far away, and sometimes it doesn't, so if that's happening it'll jerk from position to position. (I usually think of them as being used to move print heads around in ink jet printers where they're attached to a gearbox etc and one "step" would be a fraction of a pixel or something, allowing for really precise movement, but of course they also allow for the very precise speed changes needed for quadrotors.)

So if it's jerking then it's a coil not turning on at all, or when it should, but it could be caused anywhere that the coil or the timing of it is interfered with. (I'm assuming there must be rotor position sensors as well to provide feedback so anything screwing up one of those or the associated electronics could be causing it, same as a coil not working.)

This is all assuming that nothing is bent and there's no actual mechanical problem causing an irregular gap between stator and rotor, irregular friction, etc. So I'm basically just talking about what could be wrong from a circuit perspective. Fortunately for me it was just something like crap in the motor or a water droplet, but in your case it could be a crack in a board or broken wire (especially if somehting got bent).

Edit: What Singapore_phantom said, but I'd also suggest compare how it "feels" to the other motors. These types of step motors will normally be attracted to the center of the poles on each step position so you'll feel the magnetic pull at each step position when turning manually, even when powered off. (At least on mine I do.)

 

[singapore_phantom]

Ya, good point RJ. I also felt something wasn't quite right when I slowly hand-spun one of my motors after a dusty landing. It felt a little "gritty", not the same as the other motors, which all rotated freely when I pushed the props by hand. But whatever it was that was causing the issue, it fell out after tapping the craft gently while holding it upside down.

So yeah, try to get as many clues by seeing, feeling and hearing for anything untoward.

 

[rjstone]

Oh, and rather than try to recite stuff off the top of my head that I barely remember, I should probably just post these links:

http://en.wikipedia.org/wiki/Brushless_ ... tric_motor
http://en.wikipedia.org/wiki/Step_motor

Technically you have a brushless motor, but the distinction is kind of minor for purposes of getting the basic idea and the step motor article has better visuals for understanding how they work. This is more info than you need of course but the basic concepts would probably be helpful in figuring out what is wrong.

 

[oscar19]

same problem here...

Wow, I'm not the only Chicago local to have the same problem.

I recently crashed my phantom 2 into my house, and am now seeing the same symtoms you mentioned of a "sticky motor". I would love to hear how you resolved this and also is there a local dealer (Chicagoland area) I can go to for parts/repairs.

Most important for future reference; what are some reputable dealers to use where I can send my drone out for repair and have a good job done in a reasonable amount of time for a reasonable price? I'm not much of a handyman and expect to need this service eventually.