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Speed 700 BB turbo

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Speed 700 BB turbo

Home › Forums › R/C & Accessories › Speed 700 BB turbo

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  • 12 November 2014 at 12:32 #53583
    Howard
    Participant
      @howard79726

      I have a Graupner 700 BB turbo motor with which which I would like to drive a 900mm MTB planing hull via a 40mm prop. The motor is rated at 12V according to the sticker on its side, but with a range of 7.2V to 19.2V also shown. I would also like to use a LiPo battery, but given the motor spec, should I use a 3S at 11.1V or 4S at 14.8V. In other words, what is the safe and sensible way of interpreting these voltage guidelines? I am sure many of you would suggest I use a brushless setup, but this motor has been languishing in its original packaging for some time now, and it seems a shame not not to use it!

      Howard

      12 November 2014 at 12:32 #5340
      Howard
      Participant
        @howard79726
        12 November 2014 at 13:16 #53586
        Dave Milbourn
        Participant
          @davemilbourn48782

          Howard

          Why not try both of them and stick with the one which best suits the model and you? Just keep the motor bearings lightly lubricated and don't run the model flat out all of the time. The 12v is simply the nominal rating at which Graupner quote the statistics.

          Dave M

          15 November 2014 at 09:08 #53640
          Howard
          Participant
            @howard79726

            Dave

            Thank you for the advice – common sense I guess, but I was just a little unsure of how to interpret these and similar motor statistics.

            Just finished reading your treatise 'Radio Ga Ga!' in the MB Winter Special. It's a real help; nicely written and put together. I shall save it alongside 'But I don't understand Electronics' from last year in my 'Special' ring binder!

            Howard H

            15 November 2014 at 09:44 #53641
            Dave Milbourn
            Participant
              @davemilbourn48782

              Thanks, Howard. Paul Freshney has already commissioned article #3 in the trilogy. All I have to do is research it!

              Dave M

              21 November 2014 at 01:05 #53736
              Geoff Sleath
              Participant
                @geoffsleath41411

                Within reason the voltage rating of a motor isn't very critical. What is critical is the current and that will depend to a large extent on the load you impose ie the prop size. Using a higher voltage battery may mean you need to use a smaller prop which will run at a high speed. Whether you use a small, high reving prop or a larger one at lower speed depends on the model I would think.

                As a warning, my motor expertise is with electric aircraft but I can't see that airs crews are going to be that much different from water screws when setting motor currents. They're just operating in a different fluid

                Geoff

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