Cinestar 8 Upgrade for Medium Heavy Lift (8-10kg)

Discussion in 'Cinestar 8' started by Steve Maller, Jan 3, 2014.

  1. Steve Maller

    Steve Maller UAV Grief Counselor

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    I am rebuilding my Cinestar 8 as a heavy (or heavier...8-10kg) lifter using these bits:
    • existing 450mm Cinestar frame, but reconfigured as an X8 with 4 booms instead of 8. May go with longer booms eventually depending on camera angles and prop clearance
    • Avroto 3515 motors (decided against 3520s because Jim from MontoRC said at the weights I’m targeting, the smaller motors will be more efficient)
    • Props TBD, but likely 15” or 16” APC MR props. Going to experiment with different sizes top and bottom. Like maybe 15” tops and 14” bottoms.
    • MK FC 2.5 and existing Navi control
    • MK Okto XL Combi V3.0 (decided against Double Quadro 2XL for same reason as smaller motors...plus cost)
    • Going to run it at 6S using dual 8000mAh LiPos, but am going to mount them on outriggers like Ziv Marom is doing in the picture below. The 6S batts are so heavy that I think putting them closer to the vertical CoG is going to make the copter more stable and flexible with different cameras.
    Note: this is not my copter. It’s Ziv Marom’s from ZM Interactive.
    1559332_626455687411066_1564825060_o.jpg
     
  2. Brad McGiveron

    Brad McGiveron Active Member

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    Another X converted!! :D


    Looks like a nice build Steve. Looking forward to seeing how it goes.
     
  3. Steve Maller

    Steve Maller UAV Grief Counselor

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    He has seen the light! :)
    Me, too. ;)
     
  4. Devin Card

    Devin Card Member

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    Awesome! Keep us updated! Why the avroto motors over the MN4012 that quadrocopter is selling for $90?
     
  5. Dave King

    Dave King Well-Known Member

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    Steve
    Are you sure that's the board to go with as they are rated at 30amps per BL. The 2.0 BL's are rated to peaks of 40amps.
     
  6. Shaun Stanton

    Shaun Stanton Active Member

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    I will be interested in the results as well. In theory with 6S batteries you should be using significantly less current than the 4S depending on motors. I suppose for carrying 5D's and GH2/3's this board will be fine. Right now BL 2.0 4S it seems the typical average current for carrying a 5D with some heavy glass is around 12-15A for normal flight including climbs about 10 ish for hovers, some less some more depending on the climb rate etc. You should expect to see about 6 to 8 amps per BL with a 6S probably 5A per BL in a hover. Probably, you will see around 10-12A if carrying a RED type camera with some descent glass I would guesstimate.

    The question being that now the copter will suitably fly Canon 5D's SONY FS-100/700's safer with a BL Gimbal. Will the copter back to square one when carrying a kitted out RED, meaning it will do it but will require a FAN to keep the BL's cool? My guess is that issue is still going to show itself in certain configurations and probably will require the fan. It seems that fan works well as it does appear that temperature seems to be the culprit.

    It almost seems that the solution to using MK BL's for a real heavy lifter is to use 8 single BL's tied separated with enough distance to prevent the adjacent BL's from transferring heat to the entire system. This is why I am not a fan of the bL ring because it is simple thermodynamics that the heat goes from one bl to the other in a viscous cycle. My guess is that the heat transfer is not endangering the individual MOSFETS, more so than possibly damaging the micro-controller that is being used to send the small-signal pulses to the MOSFETS.

    But none the less i will be interested in the performance of these new BL's as well. The fan does seem like a viable solution if need be.

    Shaun
     
  7. Steve Maller

    Steve Maller UAV Grief Counselor

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    Actually, Holger wrote to me and I decided to go with the bigger board after all.
     
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  8. Shaun Stanton

    Shaun Stanton Active Member

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    That's awesome that picture's driving nuts! I missed my package of last today that had my remaining bits and pieces to start my HL build. I am going to start piecing as much much together for my Cinestar8 WKM this weekend :)
     
  9. Steve Maller

    Steve Maller UAV Grief Counselor

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    Which picture’s driving you nuts?
    Good luck with your build. I bet it’s gonna kick ass!
     
  10. Steve Maller

    Steve Maller UAV Grief Counselor

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    Motor mounts arrived this morning from FamousHobby.
    I’ll pop out the press nuts from one of each pair, and use my aluminum boom clamps for the coaxial configuration.
    Avroto 3515 motors arriving later today.

    IMG_8869.jpg
     
  11. Shaun Stanton

    Shaun Stanton Active Member

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    I just mounted my motors to those mounts. The press nuts pop out pretty easy for the bottom motors.
     
  12. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    If the press nuts prove tough to get out, I put a short M3 screw into the press nuts from the far side and then use a tiny little C-Clamp (In the UK G-clamp), offset so that it misses the press nut on one side but rests on the screw on the other -- and tighten it up gently and it pushes the press nut out without damaging the thread.

    Andy.
     
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  13. Shaun Stanton

    Shaun Stanton Active Member

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    Fortunately they are not that hard as the FF mounts. If you put the bolt on the other side al you have to do is wiggle them a little and they pull right out fairly smoothly.
     
  14. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Excellent! You can pull'em out with your bare teeth! :)
    Andy.
     
  15. Steve Maller

    Steve Maller UAV Grief Counselor

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    I have a technique that involves chewing gum, a broadsword, and a pint of ale.
     
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  16. Dave King

    Dave King Well-Known Member

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    Question for you Coax guys. Does the boom length make any difference in efficiency? What I mean by this is for example say you build a X4 with 450mm props and you run 16" props, would there be any differernce in efficiency if you run 550mm booms with the same props? I would imagine that the efficiency is all in the weight of the copter, motor selection, and prop selection provided you use the same batteries?
     
  17. Steve Maller

    Steve Maller UAV Grief Counselor

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    As always I have to preface comments of this nature with the disclaimer that I’m not an engineer, and this is just my uninformed opinion.
    And as such, I believe that the raw efficiency of the platform WRT lift and payload is unaffected by the boom length. However, there are a couple of issues to consider.
    1. Structural integrity: the copter’s lifting capability is generated at the ends of the booms, and the payload is hanging off the middle. So structurally, the longer the booms, the more the stress on the hub’s joints. There’s also more opportunity for resonance.
    2. Maneuverability: yawing in particular is a side effect of centrifugal force, and I would assume that the yawing capability of a copter may be adversely affected by the distance between the motors. Ever try the experiment in a playground merry-go-round where you measure the speed depending on how close to the middle you are? You definitely spin faster when you’re in the middle, as opposed to the outside.
    Another advantage of an X8 vs. Flat8 is that you can run significantly bigger props with shorter booms in the coaxial config. That will have a positive effect. I’m planning to keep my 450mm Cinestar booms as is. I can easily run 16” props in X8.
    I imagine that there might be aerodynamic justifications for moving the pairs motors farther away from one another.
    I’d love to see an actual mathematical model of this, as adding 50 or 100mm of boom length is easy, but I hesitate to do it just because it might look better and cooler. :rolleyes:
     
  18. Steve Maller

    Steve Maller UAV Grief Counselor

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    Shaun,
    Are you using a washer under the bolt head on the top of the motor mount?
     
  19. Dave King

    Dave King Well-Known Member

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    My backets are similar to yours and I am using a spacer.

    HL01-6.jpg
     
  20. Michael McVay

    Michael McVay Active Member

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    Steve or Shaun: Could you please measure the distance between the insides of the press nuts on those motor mounts (the long side)? I am trying to determine if I could get U7s on them or not. The U7 is 60mm wide and tapers in to a little under 55mm at the bottom of the motor. I would like to try them in a coax set up so I need enough room to have decent access to both ends of the bolt.

    I had gotten the ones Dave has (above) and they are only about 26mm between the press nuts so they are no where close at all.

    Thanks!
     

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