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Soldering motor cable

Posted by Óscar Moreno García on September 17, 2014 at 7:28am

Hello,

My problem is the following: I had an unfortunate crash and one of the cables of a motor (the red cable, which I suppose that is the power cable) broke. The rest of my quadcopter is fine, I tested everything and it works.

Due to living in Spain, ordering a replacement motor from 3DR (the motor is the blue one from 3DR) would cost me 70$ thanks to shipment costs. What I thought was, could I solder the cable with tin and see if it works fine?

I haven't done it and I am asking for your opinions. Is doing this viable, will the motor receive proper amperage so that it goes more or less equal with the other 3 motors.

I also want to ask if it's possible to replace the motor with another different 850kv motor from EMAX.

Thanks in advance to anyone giving it's own experience, advice or thought about this.

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Tags: cable, crash, issue, motor, motor cable, power, solder
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Replies

  • bill bergovoy September 18, 2014 at 10:59am
    After a crash I check how freely each motor rotates without power. Just soon the blade by finger.

    Sometimes diet week hey into the motor or sometimes the bearing gets damaged, or the shaft is bent.

    I've learned to buy extra motors and how to rebuild then and change bearings and shafts.

    Some people would suggest tossing the questionable motor out as it is untrustworthy. But after watching how and where motors are made I chose to maintain motors.

    And fwiw do Jr oil the bearings. It will just attract dirt and debris
  • Óscar Moreno García September 18, 2014 at 9:33am
    The wire is soldered, however, I can spot a power loss in the motor as it flies unstabilized just after doing the accrlerometer calibration.

    Also, during the test flight, there was a front left motor failure, so the quad flipped (at 1m altitude) Iran the test motors in the console and the motor that failed couldn't spin in one direction (it spinned to the left a bit and a bit to the right, as if it was oscillating). I have no clue about what caused the motor failure (temperature was same as the others). Could it be an ESC failure?
  • OutbackUAV.com September 17, 2014 at 8:32pm

    Nice neat cut! 

    Do worry too much, put some solder on each end first then join them together.

    Almost all solder has flux, don't worry about NASA quality connections unless you're sending your copter into space.

    So long as the two ends are joined and the area of the join is the same or greater than the diameter of the cable and there's a bit of tape around it then you should be perfectly fine.

  • MR60
    Hugues September 17, 2014 at 11:17am

    you can resolder easily you motor wire, based on the picture you posted.

    1-strip about 5mm of the red silicon on each piece of wire

    2-Tin each tip with solder : do not hesitate to put lots of solder on the tips

    3-place the two 5 mm tips parallel to each other and overlapping (ask a second person to hold the two tips for you , so your own two hands remain free : one to hold the solder wire, the other to hold the solder iron)

    4-Melt the pre-tinned tips with the solder iron. Once you see the solder melts , remove your solder iron and let it cool

    5-wrap the solder with insulation tape

  • Chim Xotox September 17, 2014 at 7:58am

    A problem sometimes - not always - is if the motor wires (usually on cheaper motors) are coated with insulation lacquer or such (the wires inside the motor are treated like that). If so, then that must be cleaned off chemically and/or manually or the solder won't work.

    You can test for this if you cannot tell visually, simply twist the wires together and see if the motor runs (or check for continuity if you have a meter). 

    Other than that it is like any other electrical connection so if the joint is good there will be no effect on performance.

    By the way, the three motor wires are all the same, there is no meaning to the colors - to reverse a motor, switch any two wires, it does not matter which ones.

    Replacing a motor with one that does not match but has similar specs should not create a problem, so long as the ESC is happy with it. The flight controller does not know what is out there on the arm, it only knows the results of its commands -- there could be a hamster in a wheel out on an arm, it wouldn't matter if it does the job. 

    Remember to confirm rotation direction and change if needed as described above. I would compare temperature of the motor and ESC after a test flight to see that they are more or less the same as the others.



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