Coaxial Cinestar...

Discussion in 'Cinestar Misc' started by Benjamin Rowland, Jan 26, 2013.

  1. Benjamin Rowland

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    Kopterworx posted a video the other day of a coaxial Cinestar that they built and it got me thinking about coaxial multirotors. The pros and cons of these arrangements are fairly well known in this hobby/business, but I'm hoping that folks on this forum can share their personal experience. What I'm really curious about is performance in the wind. Is a coaxial really better in the wind? I'd love to hear your thoughts on this. Thanks!

    Here's the video I mentioned:
     
  2. Thijm

    Thijm Member

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    I can tell from experience that it handles wind better then the conventional way. But its an real pain to balance motor/props.
    The only way if you want to lift more then 5-6Kg. Otherwise the copter gets to big.

    Image was our first try back in may '11
     

    Attached Files:

  3. Howard Dapp

    Howard Dapp Active Member

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    I'd be curious in hearing someone's experience converting over to coax as well. The overwhelming verdict is you lose some efficiency. I'd love to hear about other flight aspects, mainly overall stability compared to a flat layout and stability in wind, as mentioned by Ben.

    Maybe we can promise Josh a FF Moderator status if he produces a "CS8 Conversion to Coax X8" write up similar to his heavy lift thread:D
     
  4. Howard Dapp

    Howard Dapp Active Member

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    Interesting. Do you feel the effort is worth it? Wind performance is good but what about endurance compared to a flat layout. Do you feel you'll achieve longer flight times if your coax hexa was a flat laid out dodecagon? (fun word to type..dodecagon dodecagon)
     
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  5. Thijm

    Thijm Member

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    When using different props >bottom>top. At best, efficiency goes down 10-15%. But difficult to compare (lighter frame) But who cares about flight times when its more then 8min!
    It's also possible to fly with higher gains while carrying heavier payloads
     
  6. Howard Dapp

    Howard Dapp Active Member

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    True indeed!
    Now question, Are you currently still flying your coax? When flying your Epic, would the flat layout be your first choice or would it be the coax?
     
  7. Thijm

    Thijm Member

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    Currently flying the flat octo. Thinking about building an coax again. But for us this only make sense if we have a gimbal that can handle some copter vibration.
    If i can modify my current Cs gimbal to direct drive so that it can handle heavier lenses i might just move to x8
     
  8. Josh Lambeth

    Josh Lambeth Well-Known Member

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    Hey if someone wants to help in the cost to do this im all for it! :D

    P.S.
    52725_10151213973218550_1850564108_o.jpg
     
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  9. Howard Dapp

    Howard Dapp Active Member

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    What size props do you have mounted here? I'm curious if using a 14x4.7 top prop and a 13x6.5" bottom prop would be a good setup (I have these props lying around unused)? Maybe the pitch being steeper on the bottom isn't good even though it's a smaller diameter prop? Some guys are setting up the top props to spin faster than the bottoms, have you done this as well?
    [​IMG]

    Thanks!
     
  10. Thijm

    Thijm Member

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    Normal Coax setup is Bottom larger then top. This setup was top/bottom same prop > 14x4.7> Correction made in the koptertool.
    So i guess 13x6.5 and 14x4.5 wont match.

    Thijm

    [Info]
    Name=Hexa_12coax
    Version=1
    [Gas]
    Motor1=64
    Motor2=64
    Motor3=64
    Motor4=64
    Motor5=64
    Motor6=64
    Motor7=54
    Motor8=54
    Motor9=54
    Motor10=54
    Motor11=54
    Motor12=54
    [Nick]
    Motor1=64
    Motor2=0
    Motor3=-64
    Motor4=-64
    Motor5=0
    Motor6=64
    Motor7=54
    Motor8=0
    Motor9=-54
    Motor10=-54
    Motor11=0
    Motor12=54
    [Roll]
    Motor1=-64
    Motor2=-64
    Motor3=-64
    Motor4=64
    Motor5=64
    Motor6=64
    Motor7=-54
    Motor8=-54
    Motor9=-54
    Motor10=54
    Motor11=54
    Motor12=54
    [Yaw]
    Motor1=-64
    Motor2=64
    Motor3=-64
    Motor4=64
    Motor5=-64
    Motor6=64
    Motor7=54
    Motor8=-54
    Motor9=54
    Motor10=-54
    Motor11=54
    Motor12=-54
     
  11. Howard Dapp

    Howard Dapp Active Member

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    Great, thanks. For kicks I'll test a X8 coax using this config with 13x6.5 props.
     
  12. Thijm

    Thijm Member

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    Nice! But don't copy paste my settings > got the motor/BL wires wrong so some settings are reversed
     
  13. Howard Dapp

    Howard Dapp Active Member

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    Ummm yeah coax rocks! Waaaaay more stable than a flat layout. I thought I had solid yaw hold running a flat 8 layout, well I REALLY have solid yaw hold with the coax it's amazing how well this bird flies and how stable it is. Very smooth and much more wind resistant. I've confirmed that you're ONLY losing about 7-8% thrust running a coax config but the stability gains and flight smoothness totally overshadows a measly 7% thrust loss. I'm excited! No more 8 armed freaks. Feels like I'm flying a quad again but on steroids. Nice and compact, easy to transport and only 4 arms to remove. Funny thing is I'm using the same MK gyro settings as the flat layout and it flies perfect.
     
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  14. Benjamin Rowland

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    Howard, thanks for that feedback - I appreciate it!
     
  15. Pavlos Antoniou

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    Hmmm you make me want to convert my cs8..!
    You have the same props up and down?!?

    ALso can you tell me why you do you think that it is better???

    The Flat must be better because there is more surface ... ( i dont know how to tell it in english..)

    One think that i can think so is that the coaxial is easier for the Controller because it like a Quad..!

    Also BEN (thats for you as i know you have HFpro) hoverfly prefers flat octo from Coaxial..!
     
  16. Howard Dapp

    Howard Dapp Active Member

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    -Yes, using same props (13x6.5") top/bottom with a 64/71 motor speed difference in the MK mixer.

    -Why do I think it's better? It feels more stable in the air, more planted compared to flat layout. Don't get me wrong, my flat 8 flew extremely well but the coax feels much more solid and less influenced by wind. Also yaw control is better and stronger compared to my flat layout. Motor distance is 890mm so it's not a huge machine. In addition, when I'm ready to use larger diameter props, I don't have to change boom length so the coax will remain the same size. To sum it up, stability and size, transportability are the advantages.

    -My none scientific theory as to why an X8 coax is more stable (as confirmed by many) because there is more distance in between each spinning prop = less disk surface for wind to catch and more space for wind to pass through compared to a flat layout where each spinning prop are within an inch of each other.

    Give it a try...you'll love it.
     
  17. Pavlos Antoniou

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    ooooo DOnt do that...! I think i am ready...!!! :( :( :(

    THe down props goes as the up props?? letters UP??

    I know that the UP motors have CW props and turn CW and the down motors have CCW props and turn CCW...

    RIght?

    Also whats the Con if i put different props up and down?

    On coax is better to put APC 14x4.7 or Xoar 14x4 ??

    Thank you!
     
  18. Howard Dapp

    Howard Dapp Active Member

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    reply below..

     
  19. Pavlos Antoniou

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    Hmmm you have MK.. so it might be better for MK and not for Hoverfly.. :) :)

    Benjamin you go first or i go?? :)
     
  20. Brad McGiveron

    Brad McGiveron Active Member

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    I have a WKM in X8 which handles very nice and recently with some spare parts kicking around from various en devours, threw together an xy8 with MK stack, CS center plate, booms and QC motors. I used just the good ole APC's here and it flew great.
    Sorry no on board footage yet as this was just a weight test with the GH3 but it went for around 10 mins on two 6200 4s quadropowers.

     
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