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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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.

yea, you can solder these wires together.  or use a crimp connector, or any choice to complete the circuit.

I would not 'pre-tin' the wires nor add any extra flux.. the solder has a core that is filled with flux.

splices should vary for each application and situation...

this connection, although it is critical to maintainng flight is not needing nasa standards. ps I dont think nasa will allow a splice..  a broken wire will get replaced... )

anyways... these wires are high strand count wires.. I would just streip the insulation a short bit, then shove the wires 'end to end', to try to inter-mesh the strands... as far as you can. it wont be easy as the strands are fine/small and will bend.. but do your best..

youwill probably need help by a friend to hold things...

then solde the interwoven wires. 

oh, btw, if you can find some heat shrink,  put that on first...

the reason I am not suggesting the 'twisting' of the wires, is that you dont have enuf wire to get a sufficient number of twists to make a difference, and then the wires will be shortened and pulling on the other ends..

you can add wire but that would mean two spliced connections... 

anyways, good luck


I soldered the cable but I want your opinion before I put the shrinking tube on the solder.

Is this soldering OK (I'm not the best one at this, but I think it'll do the job).
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?
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

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