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  1. #1
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    Unhappy RPM's in and out at 60% and higher throttle

    Help! I am stumped with this problem. I recently received a used 'pede 4x4 vxl, and have loved it so far! One problem though, that irks me and my OCD, is that whenever I have it at full throttle, the RPM's go up and down, not really to a beat but more random. it almost seems like it's going on and off, like a capacitor in the esc handles that portion of the throttle or something, and it's glitching. I have seen one other thread on this, but it was way back in 2011, and nobody really said that (if they) solved the problem. Link will be at the end of this post. Running vxl 3s, a 3s, 5000mah 50C and a 2200mah alike, both have this issue. Gearing is stock, 11/54 and i have the mesh set properly. I have cleaned out the motor, and it has made no difference. I haven't the slightest idea what this means, as i can still pull wheelies and all that jazz. Hope someone can help!

    https://forums.traxxas.com/showthrea...top-end-speeds

  2. #2
    RC Qualifier GotNoRice's Avatar
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    The only time I've seen something like this was when the slipper-clutch was a bit loose (or simply worn out). This, in conjunction with the rev limiter.

    Basically, at full speed the slipper-clutch begins to slip, which causes the motor to over-rev and hit the ESC's rev limiter, at which point the motor slows down and the slipper-clutch re-engages. Rinse and repeat.

  3. #3
    RC Racer
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    Does is accelerate normal? If you pin from a dead stop does it have issues? Could be a loose/faulty connection somewhere. Like the battery connection.

    Sent from my SM-G970U using Tapatalk

  4. #4
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    Steve, I can pin it and it goes like a rocket. no problems on the low end.

    Rice, Thanks for the opinion, I will check the slipper and the center diff for any slipping, and will update you on my success (or failure.)

  5. #5
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    update: I unmounted the motor, and it still did the skippy thing. i believe it is the motor, as i plugged in my 20t stinger (brushed) and it revved up just fine. As of right now, I have broken my driveshafts, and am waiting on my new metal ones. I will also order a new BL motor and test to see if it works fine. I'll post what fixes the problem, for anyone else who may have this problem

  6. #6
    RC Champion RazorRC22's Avatar
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    Maybe a loose wire on the motor.
    youtube.com/c/RazorRCvideos

  7. #7
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    Update: I flashed a light inside the motor, and the magnet looking things that directly surround the rotor are rusty. I was thinking that this would cause a problem in the low rpms too, but maybe i'm wrong.

  8. #8
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    Would a 50C battery cause this? The recommended C rating in the manual is 20C.


    Edit: I have found that it would, as the esc can take 50C, but the motor is rated for 65A constant, 100A burst. I believe that this is what is causing it, and I will order a new battery and see how it goes.
    Last edited by Nill_Wrench; 06-08-2020 at 11:00 AM.

  9. #9
    RC Qualifier GotNoRice's Avatar
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    Quote Originally Posted by Nill_Wrench View Post
    Would a 50C battery cause this? The recommended C rating in the manual is 20C.
    No, the 20C recommendation is a minimum. There is no situation where having a higher battery discharge rating is a bad thing.

    Also, earlier, you said that you were having the same problem with two different batteries (5000mah and 2200mah). Even if both were 50C, the discharge rating is relative to it's capacity, so a 50C 2200mah pack would have discharge equivalent to a ~22C 5000mah pack.
    Last edited by GotNoRice; 06-08-2020 at 12:17 PM.

  10. #10
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    Yeah, I realize that. But if i get a 20C 3000mah pack, the output amperage would be almost exactly the same with the motor's specs. But if others are using 50C (any 50C really is over the motor's draw) then I guess that narrows it down to the motor. I know the ESC is fine, as I explained earlier, so I will be waiting for my new driveshafts and a cheap BL motor. Thank you for your help!

  11. #11
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    Alright, the problem revealed itself, and the esc emitted magic smoke, so now I guess i'm going castle creations. Thanks for all you help anyway!

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