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  • #1

    Vbar tail gain

    Hi Guys and Girls,

    Something doesn't seem right with the tail on my vbar. i am running it with main blades off and tail blades on, on the bench.
    I don't seem to be able to get the gain up above 40 with out getting some mega tail wag. seems to sit happy at about 30. I'm not sure if it is down to vibrations, getting about 900-2000 depending on the head speed. is this abnormally high ?

    I have tried moving the sensor around with not much effect and i cant really see anything that appears to be binding. short of of stripping the whole head and cleaning it or taking the sensor off my 7hv to check if there is a problem with that I'm not sure what to do. is there something that is notorious for causing vibes on the goblins ?



    all ideas and advice greatly welcomed

    Ben
    Trex 500- Goblin 770-Goblin 700 Black Nitro- E700 x2-DJI F550 FPV-DJI Mavic Pro-Tiny Whoop fpv
    Tags: None
  • #2
    As far as I know you can't do tail gain on the bench and you ought to have the rudder control disconnected as well.
    Member of Mk Heli Club



    GRAMMAR: The difference between knowing your shit and knowing you're shit!

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    • #3
      Hi there it might be vibration linked as i have
      the silverline on 700n dfc and at the wkend
      my vibe analysis maxed at around 450 in a hover
      and 700 on the ground

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      • #4
        I agree, you cannot test it on the bentch, as the gyro does not correctly sence the movement it is trying to correct, hence it is over correcting and that starts the wag.
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        • #5
          I would have thought running it on the bench is not a true guide to vibration levels. If you want to test for vibes, I would run with out main or tails (as mentioned).
          Cheers,
          Simon
          --------------------------------------------
          Trex 700N & E
          Futaba 18mz and some planks !!

          x 2

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          • #6
            You can put the tail blades on but it needs the control rod disconnecting to allow the blades to self centre. Do both on and off and look at the difference.
            Member of Mk Heli Club



            GRAMMAR: The difference between knowing your shit and knowing you're shit!

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            • #7
              yeh that would make sense, not torque from the main blades or anything so its not going to be accurate. ill stick the blades back on and get it into the air tomorrow and see how it goes. will start with a low gain just in case and work up

              thanks for the advice guys.

              Ben

              didnt see those last two before i posted. i ran it with tails off as well earlier and then it was absolutely fine. so i guess all should be ok. was just being a bit cautious because of it wigging out the other day as i couldnt get the settings right with the servo i was using. took the 272 off and now have a 256hv on instead so hopefully that will have helped.
              Last edited by Heliben; 19-02-2013, 09:22 PM.
              Trex 500- Goblin 770-Goblin 700 Black Nitro- E700 x2-DJI F550 FPV-DJI Mavic Pro-Tiny Whoop fpv

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              • #8
                Ben,

                Personally I would set the gains at the recommended levels.
                Cheers,
                Simon
                --------------------------------------------
                Trex 700N & E
                Futaba 18mz and some planks !!

                x 2

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                • #9
                  i tried to get her in the air today, it went less than well. as it was spooling up the cyclic started to go crazy and nearly rolled over. tried a few more times after changing around the gains and sensor position. still the same thing.
                  so i called mikado and told them what was happening and if it could be a faulty sensor. which i think it is. pulled my sensor of my 7hv (blueline) and stuck in on and did a blades off run up. the vibrations never went past about 60. bearing in mind that the silver line was registering 150-200 when just the electronics were turned on, compared to the 6 from my other sensor.

                  so i think its time to send it to mikado for replacing.

                  i have had some bad luck with my electronics on this build, what with this and my yge esc having a duff phase sensor it has been a bit disheartening.

                  good thing i guess that my eyes are set on a nitro for the next acquisition
                  Trex 500- Goblin 770-Goblin 700 Black Nitro- E700 x2-DJI F550 FPV-DJI Mavic Pro-Tiny Whoop fpv

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                  • #10
                    Yup definitely sounds knackered to me. Hopefully they'll be swift in repairing/replacing it for you.
                    Harry

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