My new MK heavy lift copter project

Discussion in 'Cinestar 8' started by Dave King, Jan 4, 2014.

  1. Chris Fox

    Chris Fox Active Member

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    you could experiment with a faraday cage ... that would be fairly simple to implement ..... take some old metal flyscreen ... possibly bond it to a substrate, thin piece of plastic, and place it under the NC and above the batteries .... In theory it would eliminate EMI from reaching the GPS/NC Combo ... A piece of carbon plate may (and it is a big may) be conductive enough to partially work at blocking the EMI .... it seems to work at blocking video transmitter signals ;)

    I wouldn't put the faraday cage around the GPS/NC combo though, then it is going to block out the signal from the sky ...

    Andy will chime in in a moment about copters and tin foil hats ;)
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Not really...there is something call mu metal which can reduce magnetic fields, but it's not clear whether the issue is magnetic or radio frequency fields. For radio frequency you can try a Faraday screen or cage, but the problem with aircraft is there is really not such thing as "ground" to which you can attach the Faraday screen -- the "ground" is really "just the negative side of the battery" and the RF noise might be just as bad on that line too. If you can find metal window screen material, you can fab a Faraday screen from that.

    Andy.
     
  3. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    G'day, Chris. Sorry, we posted more or less simultaneously.

    I was actually going to mention the tin foil cod-piece that I believe Mr. Maller has experimented with. It didn't work well as I recall, but it amused passers-by. ;)

    Andy.
     
  4. Jose Luis Ocejo

    Jose Luis Ocejo Active Member

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    How about placing the batteries some how under the booms a bracket would have to be made to get them farther away from the top GPS like on the Skyjib
     

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  5. Dave King

    Dave King Well-Known Member

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    Steve I was going to try moving the NAV board higher up but I didn't want to move the FCB any higher and I didn't have long enough cables to connect the FCB to the NAV. Are you still using the OSD board? If so how are you mounting it? Another thing I wanted to ask you is that you seem to have a good amount of space between the GPS and the NAV. I thought they were supposed to be together as close as possible?
     
  6. Steve Maller

    Steve Maller UAV Grief Counselor

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    Not using the OSD board right now.
    Why don’t you want to move the FCB?
    And there’s no reason to keep the two boards that close that I can tell.
     
  7. Dave King

    Dave King Well-Known Member

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    Let me rephrase I didn't want to move the entire assembly up too much higher and snag the trunk lid but I guess I could have gone higher. Right now I just put it all back to boom 1 as I need to be spending all my time with the gimbal.
     
  8. Bryan Harvey

    Bryan Harvey Member

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    What about RF shielding fabric? I have some from a job I did on aircraft carrier flight decks.
     
  9. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I think the RF shielding fabric is just another name for a Faraday screen, Bryan -- could be wrong, but doing a Google search suggests that's what it is.

    And.
     
  10. Dave King

    Dave King Well-Known Member

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    I had some downtime this week so I made some adjustments to my copter. I rewired the motor wires. I and now routing them above the booms and it made the wiring a lot more cleaner. No more big mess under the flight control board and I probably saved about 100-150 grams of weight.

    Next I went back to square one with my red brushless motor gimbal. I was using the Ipower 5108 motors with belt reduction system because it was recommended as the best combo for the RED but I just couldn't get it tuned it right. The 5108's just didn't have enough holding torque. I just installed Tiger GN85 motors on the roll and tilt and I did a bit of bench tuning with it and it seems already much better. Next step is to bolt it to the copter and do some tweaking with the gimbal hanging from the vibration isolators. Perfect timing because rain and snow is in the forecast.

    Here's the old setup.
    _MG_0439.jpg

    _MG_0448.jpg

    Here's the new setup.
    _MG_0491-3.jpg

    _MG_0497.jpg

    _MG_0499.jpg
     
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  11. Steve Maller

    Steve Maller UAV Grief Counselor

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    Dave, you are going to need some extensions for that landing gear. Look in my build thread for examples of what I did.
     
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  12. Dave King

    Dave King Well-Known Member

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    Why would I need extensions?
     
  13. Steve Maller

    Steve Maller UAV Grief Counselor

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    I find when I land in grass, for example, I need at least 3”-4” of clearance beneath the gimbal arms. If you don’t have that, you can end up with some bad oscillations and who knows what.
    [​IMG]
     
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  14. Gary McCready

    Gary McCready Active Member

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    Wow Dave. Those are some big motors! What does your gimbal with Red weigh? What are you flying CS8?
    Steve: You are really working hard on your heavy lifter, nice extension solution.
    I put plastic stops on my top bracket to keep the yaw arm from drifting too far right or left and keep the legs out of the video. I'd get really bad jello in flight. When the yaw arm hit the plastic stops, from a fast yaw, I'd get jello for the rest of the flight.
     
  15. Howard Dapp

    Howard Dapp Active Member

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    Looking good Dave! Why did you switch from belt drive to direct?
     
  16. Dave King

    Dave King Well-Known Member

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    The GN85 conversion only is another 185 grams total with cages so its not that much more. I'm about 11 pounds total payload.
     
  17. Dave King

    Dave King Well-Known Member

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    Because the belt drive with the heavier red combo just didn't work good enough for my strict standards. I just don't think it reacted fast enough either. Its my goal to have MOVI quality footage without paying the MOVI investment. I feel that the gimbal should work well enough that you shouldn't have to stabilize in post. Sometimes the clients just want the raw footage on the spot and it doesn't leave an impression when there's stabilization needed. In testing with the belt system I had to give the 5108 belt drive combo so much power that it was very vulnerable to vibrations which could easy ruin any footage. If I reduced power I could get more head room for vibrations but it just didn't have the holding power. I tuned till I was blue in the face (at least 16 hours of tuning) and it just didn't work.

    I've had a chance to attach the gimbal to the copter with the new motors running direct and do some ceiling tuning and it appears to hold much better without vibration issues. I'll put it to the test in the air by tonight or tomorrow.

    Dave
     
  18. Dave King

    Dave King Well-Known Member

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    Its been a real busy couple days working on my heavy lifter project. I spent quite a bit of time dialing in the new Tiger brushless motors. On Friday I made a made my madden flight with the Tiger brushless gimbal motors (GN85's) and I found out quickly that the new motors don't need a lot of Power. I was experiencing a lot of vibrations in the tilt axis especially when I was moving the camera up and down. I suspended the copter back to my ceiling and made some more adjustments. I went back on Saturday morning to make another test flight and I got the vibrations out of the tilt when I moved the camera up and down but I still had a lot of vibrations on the tilt access when the camera was steady. So I suspended the copter again to my ceiling and spent a few hours monitoring the vibrations in the software while making small adjustments. After I finished I had dialed the P gain on the tilt down about 40% of where I was.

    I went back early afternoon to do another test flight but my copter didn't want to cooperate. When I started the motors to take off I was experiencing a lot of sputtering and hesitation out of the motors. At first I thought it was the normal issues everyone was seeing before they adjusted the motor timing but this did not help. I started the motors again and my favorite lady spoke "major error". I noticed that motor 3 and 7 would not lighting up or spin on initial startup.

    I took the copter home and MK tools confirmed the problem. Error 17 FC to I2C to BL issue. Inspecting the board I see no signs of any issues. Nothing looks burned up or fried. So I switched out the power board for my spare one I had, do some quick tests and was able to make another flight before it got dark. I was fighting the daylight because the weather over the next couple days is supposed to be snow/rain. Got the copter back up in the air everything is back to normal flight wise. The footage is much better. It's definitely workable and all the vibrations are completely gone. Footage is definitely better than where I was with the belt drive system. I still have a little bit of work on the roll to sort out as I see an occassional movement but not very often.

    In the tuning of my gimbal I found that these motors work a lot better without a lot of P gain (thanks to Howard for that tip). I was so used to needing high gain with the belt combo that I didn't start out with lower gains and work my way upward. So I have a really good solid baseline to start making small adjustments to the roll.
     
  19. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Dave: Did you find out the problem with the "major error?" Is this another manifestation of the BL 3.0 and T-motors even after making the changes recommended by Holger?

    Andy.
     
  20. Dave King

    Dave King Well-Known Member

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    HI Andy

    The board is bad it definitely has a major failure. The motors now wont start and 3 and 7 do not light up on the board. My backup board works fine. I have an email into Holger still waiting for the responses.

    Dave
     

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