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  • #1 by Trimitsos on 14 Feb 2018
  • Does anyone has any piece of old Cobra motors that is not needed anymore?
    2205 2300KV 27788587_10156472618867697_3836445789279065061_o.jpgCOBRA MOTOR is needed pleaaaase 2205 2300KV

    I have ACHIEVED to burn the coils on one of my cobra 2205 2300KV.
    28108993_10156472784702697_1524846588_n.jpgCOBRA MOTOR is needed pleaaaase 2205 2300KV

    I live in Greece and my fpv friends here do not use Cobra motors, So I can not find any spares.

    I would really really appreciate it if someone could donate me an old motor OR just the coils....

    THANK YOUUUUU
  • #2 by atomiclama on 14 Feb 2018
  • Rewire it if you are desperate.
  • #3 by Cheredanine on 14 Feb 2018
  • So sort of like this? (Note he wire length)<br /><br />
    Those are nit old cobra, those are the champion range still available.
    The old cobra 2205s were labelled 2204
  • #4 by Trimitsos on 14 Feb 2018
  • Rewire it if you are desperate.

    I have already considered that option...
    But i don't have this knowledge.
    Moreover it must not be as simple as one might think.
    Each of the three wires consist of 3 cores. so 9 wires in total, in a very confined space.
    I am not sure I can manage, or if I get close to repairing it wthat the result will be like....

    It would be better to buy a new one or get a used one by you guys....
    :-)


  • #5 by atomiclama on 14 Feb 2018
  • The knowledge is easy to come by and the theory of the rewind is not that complicated.

    But doing it is a different matter  ::)

    Getting the boogers apart without damage is quite a feet in it's self.
    The rewind is a bit fiddly.
    The end result, that warm feeling inside that you did it.
  • #6 by Trimitsos on 15 Feb 2018
  • were could i buy cable for motor winding. i am thinking of trying it out.....
  • #7 by atomiclama on 15 Feb 2018
  • #8 by Trimitsos on 16 Feb 2018
  • <br /><br /><br /><br /><br /><br /><br />upload image<br />


    Removing the stator without damaging alluminium parts was the most difficult part...
    now I am on the market for the wires....

    @atomiclama
    Thanks for offering wires, but sending to Greece will have some posting charges anyway!
    I will try the local market these days.

    It seems the wire was 0.35mm
  • #9 by Trimitsos on 17 Feb 2018
  • I found a bit of wires.... for 10€
    0,35
    0,50 (this dimention equals with two wires (of 0,35mm diameter) in parallel - as the guy in the shop indicated)

    <br /><br />*Cobra motors had for each phase two wires in parallel, with 11 revolutions each.


  • #10 by Trimitsos on 21 Feb 2018
  • Finally done.....
    Thanks for all the info guys

    <br /><br /><br /><br


    BTW, I switched from x2 parallel 0,35 to single 0,5mm which is equivalent cable.
    Moreover I changed from 11 revolutions to 9 in order to have higher KV
  • #11 by hoverfly on 22 Feb 2018
  • Well done , heroic,   ~~.... I have only ever rewound one motor and that was for a rear window wiper motor. After that i have just coughed up for a new one.
  • #12 by VaNDAL_UK on 15 Mar 2018
  • How does it fly???


    You can't stop there!!!  :crossfingers:
  • #13 by ched999uk on 15 Mar 2018
  • Hope the flights go well. I assume you did all 4?
    I thought that changing to a single wire would change the properties. i.e. the resistance will be different as will the reluctance. Not sure if just having a single wire will have an effect as you are reducing the total surface area and if I remember my electronics theory correctly there was some thing about most atoms flowing close to the surface of the conductors and you have reduced the surface area.

    I will be very interested in how you rate the motors vs the old windings. Do they have more or less torque, better punch outs etc..

    Please post back how you are finding it/them.
  • #14 by atomiclama on 17 Mar 2018
  • Not sure if just having a single wire will have an effect as you are reducing the total surface area and if I remember my electronics theory correctly there was some thing about most atoms flowing close to the surface of the conductors and you have reduced the surface area.

    The skin effect comes into effect at high frequencies and only matters when a certain freq/wire diameter ratio is exceeded. Looked into it a long time ago and the frequencies these motors are running at it was not a problem.

     I think there was also something about multiple wire being better when run as a generator but single wires better as a motor.
  • #15 by ched999uk on 19 Mar 2018
  • You are quite right about skin effect only having issues at high freq.

    Thinking why a manufacturer would have used 2 conductors when 1 would be simpler. I wonder if it was to do with heat transfer or packing more cross sectional area of conductor in the small space.

    Hope the OP's rewound motors are doing well. I would love them to came back and give their impressions.
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