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INTERMITTENT PROBLEM WITH 3648-770KV MOTOR

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  • INTERMITTENT PROBLEM WITH 3648-770KV MOTOR

    I have a FMS P-39, Have not flown it. After I built it I found that the prop without power to the motor felt like it had tight bearings I called MRC I spoke with one of the guys who said run a battery through it on the ground and it should loosen up.

    Did that. What is happening now if i run it for awhile and then with power off turn the prop it is very stiff ( tight bearings) put after it could down spins by hand o.k.
    I removed the motor from the plane, turning the can by hand if feels fine I feel nothing in the bearings and the can turns as it should be run it gain and it gets tight....
    ANY body have any idea's???


    )
    Last edited by bobtheman; Apr 16th, 2018, 10:36 AM. Reason: NEW INFORMATION!!

  • #2
    It's because when you remove it the wires are disconnected, the motor will act as a generator when turning it by hand when it's all hooked up..
    TiredIron Aviation
    Tired Iron Military Vehicles

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    • #3
      There's a problem with the ESC. It might be cured by hooking it to the programming card and resetting it (if you have the card) It also might be a bad ESC.

      Contact where you got the model from.

      You SHOULD feel some resistance due to the motor acting as a generator, but it should still let you spin the prop.

      I have had a battery fall out of a model in flight (pushed for a tight outside loop and the sticky back velcro let loose of the EPO foam) and the prop windmilling kept the RX operating for a safe landing. That should give you an idea of how much electrically induced resistance the prop would have if the ESC is working correctly. Not much until it gets up a pretty good RPM. (proportional to RPM squared)

      ********************

      I ought to rig the plane for a repeat to get it on video, but I need a parachute for the battery. Dropping a 4S 3300 from about 100 ft is not good for it.
      FF gliders and rubber power since 1966, CL 1970-1990, RC since 1975.

      current planes from 1/2 oz to 22 lbs

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      • #4
        Ok. Pilots this is insane....I run the plane in my shop for two minutes.. disconnect the battery turning the prop very stiff I plug in the battery ( I DO NOT RUN THE MOTOR) and the prop is spins free with your finger I disconnect the battery prop stiff plug battery in again spins free disconnect power and it is stiff did this 4 times in row always the same results however after power off for about five minutes the prop spins freely with a finger....It blows my mind

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        • #5
          Originally posted by bobtheman View Post
          Ok. Pilots this is insane....I run the plane in my shop for two minutes.. disconnect the battery turning the prop very stiff I plug in the battery ( I DO NOT RUN THE MOTOR) and the prop is spins free with your finger I disconnect the battery prop stiff plug battery in again spins free disconnect power and it is stiff did this 4 times in row always the same results however after power off for about five minutes the prop spins freely with a finger....It blows my mind
          https://www.youtube.com/watch?v=RaCjJbEB078 I FOUND THE ANSWER!

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