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  1. #1

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    HELP PLEASE! Problem with Robbe U47 U-Boat running Rokraft 8367 ESC

    Hi everyone,

    Well I'm stumped.

    I acquired a beautiful Robbe U47 running the Rokraft 8367 ESC. It has worked fine for years, but has just recently started playing up.

    There are two big batteries for powering the twin motors, and a smaller, separate RX battery for powering the receiver (I was always puzzled as to why they did it that way in this age of BEC). It's also wired through what appears to be a relay. Is that what it is? I mean the blue thing next to the ESC - see picture.What is that?

    So here's the problem:


    • The motors only turn on a fraction of throttle, in both forwards and reverse. Full throttle and they stop.
    • I've re-calibrated the ESC several times, but still the same problem
    • The batteries are all healthy - they all cycled up to capacity
    • I got a 30 amp mtroniks marine ESC, and tried connecting it up in the same way as the existing set-up: Still incorporating the RX battery, still going via the relay (if that's what it is). Everything worked and the ESC responded to the transmitter, but the motors wouldn't turn over
    • I then tried a more modern, standard, simplified set-up: No relay, no RX battery, just connecting the Mtroniks ESC directly to the motor batteries. Again, everything worked and the ESC responded to the transmitter, but the motors wouldn't turn over


    Therefore, I'm stumped! I've put everything back to how it was and have started looking for another Rokraft 8367 ESC, but they're bloody expensive for what they are.

    Any suggestions?

    Many thanks in advance, really hope to hear from someone!

    Jason.
    Click image for larger version. 

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    "If I had all the money I've spent on radio-controlled models, I'd spend it on radio-controlled models."

  2. #2

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    Anyone? Anyone? Bueller?

    Otherwise, I'll just order another 8367 ESC and see if that fixes it.
    "If I had all the money I've spent on radio-controlled models, I'd spend it on radio-controlled models."

  3. #3
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    Hi,
    If you have already replaced the ESC and that didn't fix the problem then obviously that is not your problem....the reason many people have separate battery packs for the receiver (including myself, I do it too) is to prevent the esc from shutting down and the model not responding to commands should the main drive batteries go flat. True, it does create a little more hassle with batteries but what would be worse, an extra battery pack to maintain or swimming for your U-47? I personally would try an other radio, see if that fixes the problem. If that is not your problem, try the motors. The stock Robbe motors are fair at best. They draw a ton of current and over time they may have gotten even more power hungry.
    I\'\'\'\'m sorry Spanky, I have to live my own life- Alfalfa

  4. #4

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    Thanks so much for replying! The radio is fine, in that everything else is responding, so I guess it's motors next!

    What are the stock motors on the Robbe U47? Speed 600 or something? So what would be a present day equivalent of that? I mean, which motors could make eligible replacements?
    "If I had all the money I've spent on radio-controlled models, I'd spend it on radio-controlled models."

  5. #5
    subsinker's Avatar
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    I used Al Matevas setup...expensive but it is belt driven, reliable and draws less than half of what the stock motors draw. http://www.shipsnthings.com/indexNS.htm
    I\'\'\'\'m sorry Spanky, I have to live my own life- Alfalfa

  6. #6

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    Thanks again!
    "If I had all the money I've spent on radio-controlled models, I'd spend it on radio-controlled models."


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